Guide to best buiding interior finishes:
Selection, installation, maintenance - this article series discusses and provides a best construction practices guide to the selection and installation of building interior surface materials, carpeting, doors, drywall, trim, flooring, lighting, plaster, materials, finishes, and sound control materials.
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As described in the book, Best Practices Guide to Residential Construction Chapter 5, Interior Finish:
Interior finishes are the most visible and, on a square-foot basis, often the most expensive components in a house. However, since many of these products and materials are marketed directly to consumers, they are often not well understood by builders and designers.
Making good decisions on such finish materials as flooring, carpeting, and lighting fixtures can make a critical difference to homeowner satisfaction. The builder or designer can play a key role in helping the homeowner choose finishes that are well-suited to the intended use, as well as providing the structural support and prep work the materials require for good performance.
Details about installing drywall are found at DRYWALL INSTALLATION Best Practices. Excerpts are below.
Single-layer, 1/2-inch drywall is the default wall and ceiling treatment in most residential construction.
Photo at left courtesy of Eric Galow, Galow Homes.
Done well, it goes largely unnoticed. Nail pops and cracks, however, are very conspicuous and remain the leading cause of builder callbacks.
With wet or poor-quality framing, there are bound to be problems in the drywall finish. With dry lumber and proper detailing, however, drywall problems can be kept to a minimum.
Drywall consists of a gypsum core covered by two layers of treated paper. The long sides are tapered for easy finishing with joint compound. The short or “butt” ends are not tapered.
Also see CHINESE DRYWALL HAZARDS.
This material comes in four thicknesses: 1/4-inch, 3/8-inch, 1/2-inch, and 5/8-inch. A single layer of 1/2-inch drywall covers most residential walls and ceilings. For a stiffer wall and better sound deadening, use 5/8-inch drywall or a double layer of 1/2-inch drywall, with all joints staggered between layers and the second layer glued to the first for best performance.
The 3/8-inch panels are useful for covering existing walls and ceilings in remodeling. One quarter- inch board, installed in layers, is useful for curves. Special 1/4-inch bending-type drywall has the smallest bending radius.
Fire-code drywall has special additives, including glass fibers, to increase its fire resistance. Residential building codes typically require Type X 5/8-inch fire-code drywall with a one-hour rating for party walls, ceilings over furnaces, and common walls between living space and garages.
Moisture-resistant (MR) board, sometimes called “green board” because of its green paper facing, has limited water resistance from asphalt additives, and is recommended for high-humidity areas such as bathrooms and laundries.
The material is denser and less rigid than regular drywall, so it is prone to sag on ceilings unless the framing is 12 inches on-center or less. Also it will fall apart, like regular drywall, if it gets soaked. For that reason it should not be used as a tile substrate in any application where it might get wet.
This is a relatively new
product that uses an inorganic fiberglass matt instead of
paper facing, since the paper facing readily supports mold
growth. Panels are available with the fiberglass matt on
one side or two. Glass fibers in the gypsum core add
strength as well. Details about mold resistant drywall are found
at MOLD RESISTANT DRYWALL.
To prevent problems, use good quality framing lumber and follow these recommendations:
Drywall should be installed over straight and level framing. If the framing is excessively wet, it will crack the drywall and cause nail pops as it shrinks. If the framing is twisted, bowed, or out of alignment, it will cause weak points in the surface and possible cracking. Moderately bowed studs can be fixed by cutting a kerf at mid height, straightening the stud, and scabbing a section of 1x4 or plywood on either side. Repair or replace problem studs before installing the drywall.
On ceilings, it is common practice in some parts of the country to install 1x3 furring strips at 16 inches on-center perpendicular to the ceiling joists before installing the drywall. The furring is shimmed to even out irregularities in the ceiling joists and creates a more stable substrate for the drywall with less chance of cracking. Also, the furring provides a wider nailing surface for hanging drywall.
On walls and ceilings, it is best to install drywall perpendicular to the framing. This ties together more framing members and provides greater racking strength. On walls, 1/2-inch or 5/8-inch drywall can span up to 24 inches whether it is installed parallel or perpendicular to the framing.
On ceilings, 1/2-inch or 5/8-inch drywall can span 24 inches only if it is installed perpendicular to the joists and supports less than 1.3 pounds per square foot (psf ) of insulation. Otherwise, 16-inch on-center spacing is recommended. With latex spray textures or airless spraying of latex paints, perpendicular installation over 16-inch on center framing is recommended to prevent sagging.
Another way to minimize nail and screw pops is to minimize the number of fasteners. Gluing the drywall to the studs with construction adhesive allows the installer to eliminate 75% of the fasteners (Table 5-2). Using adhesives also helps to even out minor irregularities in the framing and results in a much stronger and stiffer wall. Use a construction or drywall adhesive that meets ASTM C557.
Apply a 3/8-inch bead down the center of each stud or joist, stopping about 6 inches from each end. Where two drywall panels meet, apply two 3/8-inch beads so each panel gets full contact with adhesive. No adhesive is needed at inside corners, top and bottom plates, or at bridging, diagonal bracing, or other miscellaneous framing. Also do not use adhesive over polyethylene sheeting or insulation batts with paper flanges stapled over the stud faces.
To ensure a good bond, drywall manufacturers recommend pre bowing the drywall by stacking several sheets face up with a 2x4 under each end. Left overnight, this will leave a permanent bow, forcing the center of the sheet tight against the adhesive (except in very humid weather, when the boards may remain flexible).
Push drywall panels into the adhesive with hand pressure along joists or studs. Do not apply more adhesive than can be covered in 15 minutes, or it may skin over. Allow the panels to dry at least 48 hours before adding joint compound or skim coating.
Inside corners at walls and between walls and ceilings are stress points for drywall and common places for cracks or nail pops. Leaving one side of the joint free to move without fasteners will eliminate most of these problems.
On ceilings, place the first screws 7 to 12 inches in from the corner and support the ceiling drywall with the wall panels. Also, do not fasten the top 8 inches of the wall panels. No screws should go into the top plate, where shrinkage may occur. Similarly, leave one side unfastened at wall-to-wall corners, but make sure it rests against solid wood backing or drywall clips (see Figure 5-1).
While control joints in drywall are not commonly used in residential construction, they are a good idea in surfaces over 30 feet long or at changes in floor level, such as stairway walls. On a stairway wall, locate the control joint at the top of the first-floor wall where the top plate meets the ceiling joists.
The 1/4-inch joint can be painted with the wall and left as a reveal. Another option is to omit the metal control joint and simply leave a small gap between the upper and lower drywall, and cover the joint with wood trim.
Details about drywall control joints (plasterboard control joints or gypsum board control joints) including installation specifications & product sources are at DRYWALL CONTROL JOINTS.
Outside corners fashioned with metal corner bead are also prone to cracking and nail pops. To avoid problems, do not nail into the top plate, and leave a gap at the bottom of the wall to accommodate any settling. Nail with drywall nails at 9 inches on-center on both sides of the corner, with nails opposing each other.
Newer “mud-on” or “tape-on” corner beads are less prone to edge cracking than traditional metal corner beads and, with no nails, eliminate nail popping. The corners are metal or plastic and are held in place by paper or vinyl flanges embedded in joint compound. Some of the vinyl corner beads can also be installed with spray-on contact cement. In general, tape-on corner beads require fewer coats and less joint compound than traditional metal corner beads, speeding up the finishing process.
For radiused walls, the easiest approach is to use two layers of1/4-inch drywall, preferably the “high-flex” type, if available. If not available, it is possible to wet the side of the drywall that will be compressed (the inside of the curve) with a garden sprayer or short-nap roller. Then stack the boards with wet face to wet face and cover with plastic sheeting. After an hour, install the panels with their long dimension across the studs. Minimum bending radii are shown in Table 5-3.
The building should be heated before finishing begins and maintained at 55°F to 70°F throughout taping and finishing. The cooler and more humid it is, the longer it will take ready-mixed joint compounds to dry. If necessary, use supplemental heaters and provide adequate ventilation to remove excess moisture. Too much moisture can soften and weaken the bond between the drywall and the paper facing. Conversely, if the weather is too hot and dry, paper drywall tape may not bond well and joints may experience excess shrinkage and cracking.
Mesh tape is easier to apply but not as strong as paper tape. It should never be used in inside corners, where it can tear or be cut by the trowel. However, if combined with setting-type compound, mesh tape is nearly as strong as paper tape and can produce a quality job. Mesh tape is also very useful for repairing cracks in older plaster walls or ceilings.
Many residential jobs are taped with premixed all-purpose joint compound for all three coats. While this is acceptable, according to U.S. Gypsum guidelines, installers can produce stronger joints less prone to cracking by using special setting-type compounds for the first coat to embed the tape and corner beads and patch any big holes. Do not use setting-type compound on nail or screw indents.
Setting compounds are mixed on-site and set up by a chemical reaction, rather than evaporation of the water. They dry rock-hard and do not shrink. Setting times range from 20 minutes to several hours, and the compound can be recoated as soon as it sets, rather than the next day as is typical for ready-mix compound. Durabond® 90 is the most commonly used. A new type of setting-type compound from USG, called Easysand®, overcomes the chief liability of setting-type compounds—that they are nearly impossible to sand.
For nail and screw indents, and the fill and topping coats on seams, most contractors use premixed all-purpose compound; although special topping compounds are available. Premixed compound should be stored, applied, and allowed to dry at between 55°F and 70°F, preferably over 60°F. If allowed to freeze, manufacturers claim that readymix compound can be reused if thawed and remixed thoroughly with an electric mixer, but it is probably wiser to just throw it away.
Drywall window and door trim, acute and obtuse angles, bullnose corners, and arches have been greatly simplified by the introduction of specialty drywall trims and accessories (see Buy Interior Finish Product Resources). Most profiles are available in metal and plastic in either nail-on or tape-on styles.
Standard nail-on or tape-on corner bead provides the strongest 90-degree corner. However, for acute or obtuse outside corners—for example, around skylight wells—you are better off with flexible tape-on corner trims reinforced with metal or plastic that can be set at any angle. These help at inside corners as well, such as between intersecting roof planes, where standard paper tape tends to leave a wavy line.
A variety of trim products simplify creating rounded inside (cove) or outside (bullnose) corners. These come in both tape-on and nail-on styles, but the tape-on type are less prone to cracking. Some of the plastic profiles can also be applied with spray-on contact adhesive. In general, one finish coat of joint compound is applied to the flanges only (after the embedding coat dries), so these profiles are quicker to finish and dry than standard metal corner bead (Figure 5-2).
For miters and three-way corners, some suppliers provide special trim pieces. If these are not available, the trim will need to be miter-cut with a carbide or abrasive blade, depending on the trim material.
For a simple, contemporary detail, you can return the drywall directly to the window or door jamb and trim the edge of the drywall with a J-bead or L-bead, available in both plastic and galvanized steel. J-bead must be slipped on the end of the drywall before it is installed; it creates a separation from the wood frame, which is useful where movement in the door or window might otherwise crack the finished joint. The reveal type of J-bead, called J-stop, is not mudded, as it serves as finish trim.
Shimming around the rough opening to get an even reveal around door or window jambs can be tricky. Enlarging the rough opening and attaching a plywood or pine backing to the jamb simplifies the task (Figure 5-3).
Before the introduction of specialty beads designed for curves, building drywall arches meant snipping metal corner bead every inch and bending it as well as possible to conform to the contour of the arch. A variety of bendable corner beads have simplified the task. Two of the more popular are Archway L Bead (Trim-Tex Inc.), a vinyl installed with a spray-on adhesive, and Arch-Flex (Con-Form International), a vinyl tape-on bead (see Buy Interior Finish Product Resources).
Use 2x stock, or plywood with 2x blocking in between, to frame the curve of the arch. To form a smooth curve, use two layers of flexible1/4-inch drywall around the curve. If this is not available, score the back face of a strip of 12 -inch drywall every inch and form it to the curve (Figure 5-4).
Details about interior plaster veneer finishes are at PLASTER VENEER Best Practices. Excerpts are below.
Veneer or skim-coat plaster has, for the most part, replaced traditional three-coat plaster in residential work. It consists of a single coat of plaster 1 /1 6 to 1 /8- inch thick over a special type of gypsum board, commonly called blueboard, which is treated to bond well to plaster. Although the finished job costs 30 to 50% more than standard drywall, veneer plaster has a number of advantages over drywall:
Skim coat prep work is similar to drywall with a few exceptions. Because the finish coating is less than 1/8 inch thick, the boards must lie flat in a plane. Other than that, the board can be hung pretty quickly with few concerns. The screws can be left flush with the surface, and butt joints can fall anywhere. Expanded metal corner bead goes on all outside corners and self-sticking mesh tape goes over all seams.
Some plasterers prefer to apply the finish with baseboards and door and window casings already in place, protected with masking tape, so the plaster can fill in any waviness in the board behind the trim. Otherwise, install 1/8 -inch plaster grounds at the baseboard and around all door and window openings to guide the trowel and produce an even finish.
Using a 12- to 16-inch plaster trowel, a first scratch coat goes over all flat seams and then the finish coat is applied right away. If the seams are allowed to dry overnight, they will need to be wetted first or the dried plaster will suck too much moisture out of the finish coat, leaving a weak joint. The same is true of cold joints along a wall. If a wet edge is allowed to dry out, it should be rewetted. Otherwise it will be difficult to blend the new plaster into the cold joint.
Different brands and types of veneer plaster get slightly different treatments, but in general, the finish coat is troweled on in one or two passes and troweled smooth. Once dried, small imperfections or voids can be misted with water and fixed with standard joint compound.
Wood floors provide a natural warmth and beauty like no other flooring material. And new developments in finishes and engineered products have expanded their durability, versatility, and ease of installation. Still, control of moisture levels in the flooring and structure around it remains the biggest issue influencing the success of a wood flooring installation, particularly with unfinished strip flooring, but with many of the engineered products as well.
Details and information tables about solid wood strip and plank flooring are at FLOOR, WOOD SOLID STRIP, PLANK. Excerpts are below.
Traditional unfinished 3 /4-inch hardwood strip flooring in oak or maple remains the most common wood flooring type and the best choice where heavy use and frequent refinishing are likely. While the most common species are still oak and maple, an amazing variety of domestic and imported woods have become available in recent years.
Flooring species are rated for hardness and dimensional stability (see Table 5-4 and its continuation Table 5-4b provided just below). Wood Hardness is rated on the Janka scale, which measures the force required to push a small steel ball into the wood surface. The results are often compared to red oak, which is used as a benchmark. Unless a floor with lots of “character” caused by dents and wear marks is desired, avoid woods significantly softer than oak.
Also consider the wood’s dimensional stability. Less stable woods are likely to lead to gaps, cupping, or other problems with wider plank flooring and in regions like the Northeast, which has big seasonal swings in relative humidity. Other locations where moisture movement might be a problem include below-grade spaces, slabs-on-grade without vapor barriers, or rooms over crawlspaces. In these environments, choose a stable wood and a narrow profile to avoid problems. Laminated floors, discussed below, are often the best choice for these applications.
A number of exotic hardwood imports are also now available. Many of these are plantation-raised or logged with sustainable forestry practices, but some are not. To be sure, work with a reputable importer and look for third party certification of sustainable logging practices. For more information, contact the Forest Stewardship Council or the Smartwood program (see Buy Interior Finish Product Resources).
[Click any table or figure to see an enlarged, detailed version.]
While hardwoods are harder and more durable than softwoods in general, this is not always the case. For example, heart-pine flooring, whether antique or new (cut from the centers of longleaf southern yellow pines) is nearly as hard as oak, while black cherry, a popular hardwood flooring, is 26% softer than oak.
Other traditional softwood choices are white pine, popular for Colonial reproductions in the Northeast, and fir flooring in the Northwest. While fir flooring is dimensionally stable, wide white pine boards can be expected to swell and shrink significantly, leaving gaps in the winter months. Both are relatively soft and easy to dent, creating a rustic appearance.
Narrow flooring boards up to 3 1/4-inches wide are called strips and boards 4 inches and wider are called planks. The wider the board, the greater the seasonal movement will be and the fewer the number of fasteners to resist movement.
Plank flooring over 4 or 5 inches wide has a greater tendency to shrink and leave gaps, or to swell, causing the flooring to cup or curl over time. For that reason, some manufacturers recommend additional fasteners in the face of plank flooring, either nails or countersunk screws. Also the wider the board, the more critical it is to monitor and control moisture conditions of the flooring and structure (see “Moisture and Wood Flooring,” p. 167).
The best grades of wood flooring have longer pieces, fewer variations in color (more heartwood), and fewer knots and other defects. Quartersawn grades will have much better dimensional stability, with 30 to 50% less movement than plainsawn boards.
In better grades, pieces are also likely to be straighter, making life easier for the installer.
With many species, however, the visual variations in lower grades can be attractive as well as economical.
A No. 2 or No. 3 maple or cherry floor can be distinctive and striking (Figure 5-5).
Details and information tables about the effects of moisture on wood flooring are at FLOOR, WOOD MOISTURE. Excerpts are below.
Understanding and controlling moisture levels is the key to success with wood flooring. The conventional wisdom of acclimating wood flooring to job-site conditions can cause more harm than good if the job site is not sufficiently dry when the flooring arrives.
Wood flooring installed in very dry conditions and later exposed to high moisture levels can cause problems such as cupping, particularly with wider planks. In extreme cases, the swelling planks crush the wood fibers along their edges, leaving a permanent “compression set.” Gaps appear when the flooring returns to its normal moisture content.
Wood is a hygroscopic material, meaning that it picks up or gives off moisture to the air until it reaches equilibrium with the relative humidity. As it absorbs or releases moisture, the wood swells or shrinks (see Figure 5-6). Finishes and sealers on the wood slow this process, but do not stop it.
Most hardwood flooring is kiln-dried and delivered with a moisture content (MC) of about 7.5%, which is approximately the equilibrium moisture content for wood at 70°F and 40% relative humidity—typical indoor conditions for most of the U.S.
While much has been written about acclimating wood flooring to the job site before installation, in most cases it is the job site that should be dried out before the wood is delivered. If dry wood flooring is brought onto a wet job site, the flooring will swell as it adjusts, creating unsightly gaps when it shrinks back to normal levels.
Before the flooring is delivered, the building should be closed in, and all concrete, masonry, drywall, paint, and other wet work should be thoroughly dry. The basement should be dry and the ground sealed in any crawlspaces. The goal is to have the indoor relative humidity and the moisture content of the subflooring close to the levels they will be after the home is occupied. To sufficiently dry out the site, it may be necessary to run the heating or air conditioning for a week or more prior to delivery of the flooring.
As a rule of thumb, the subflooring moisture content should be no more than 2% over the maximum normal level for that region based on the map in Figure 5-7, and the flooring and subflooring should be within 2 percentage points of each other. A moisture meter is necessary to determine these levels. Checking the relative humidity with a hygrometer is also a good idea.
With the exception of extremely humid regions such as the Gulf Coast, or extremely dry regions like the arid Southwest, wood delivered at 7.5% moisture content will be suitable for installation in a dry home. If the flooring needs to be acclimated, unbundle the boards and spread them out in the rooms where they will be installed until they reach a moisture content within the range shown in Figure 5-7 above.
Details and best construction practices for the installation of wood flooring, along with illustrations and tables are found at FLOOR, WOOD INSTALLATION GUIDE. Excerpts are below.
Standard 3/4-inch strip or plank flooring is nailed through the tongue into a sound, dry wood subfloor—either plywood, oriented-strand board (OSB), or solid planks. If installed over a slab, the subfloor can either be floated or nailed to the slab.
In new construction, the best subfloor for wood flooring is nailed and glued 3/4-inch T&G plywood, with the finish flooring installed perpendicular to the joists if possible. Research conducted by the National Oak Flooring Manufacturers Association (NOFMA) has shown that 5/8-inch plywood or 3/4-inch OSB also have adequate nail-holding ability for hardwood flooring, although OSB can swell if it gets wet.
Before installing the flooring, nail or screw any loose spots, and shim or sand down any uneven spots to prevent squeaks. Then lay down a layer of 15-pound asphalt felt, which reduces the flow of water vapor into the flooring. The added friction also helps restrict movement in the flooring. Leave a 3/4-inch expansion space along the edges on the long side of the flooring to accommodate any movement. The expansion space can be concealed with baseboard and shoe molding or by cutting back the drywall (Figure 5-8).
For below-grade installations, use a laminated flooring product. For slabs-on-grade, a plywood subfloor is required—either nailed to the slab or floated on top. The slab should be poured over granular backfill with a vapor barrier and must be dry before installation. To test for dryness, duct-tape a one-square-foot piece of polyethylene film to the floor for 24 hours. If the film is clouded or beaded up with moisture, the slab is too wet. Slabs less than 60 days old are usually too wet. Use heat and ventilation, if necessary, to speed up the drying time.
The slab should be level to 1/4-inch in 10 feet. Level any uneven spots with clean mason’s sand or a floor leveling compound. Next, lay down a 6-mil polyethylene vapor barrier.
On a dry slab where moisture problems are not anticipated, the nail-on method is preferred. Nail 3/4-inch plywood to the concrete with powder-actuated fasteners using at least nine nails per panel (Figure 5-9).
Leave 1/4 to 1/ 2-inch between sheets and 1/2-inch around the room perimeter for expansion. Start alternating courses with half sheets so the joints are staggered. Lay 15-pound felt over the plywood and install the flooring. To avoid puncturing the vapor barrier and hitting the concrete, use shorter 1 3/ 4-inch flooring nails or an angled adapter on the floor nailer.
If there is any question about moisture coming up through the slab, use the floating method (Figure 5-10).
As an extra precaution, tape the laps in the poly vapor barrier and run it a few inches up the wall. Next lay down, but do not nail, 4x8 sheets of 1/2 -inch plywood with the long edge oriented along the length of the room. Leave a 1/4- to 1/2-inch gap between sheets and 3/4- inch around the room perimeter.
Next, lay another layer of 1/2-inch plywood oriented at 45 degrees to the first layer with the same spacing, and staple, screw, or nail (7/8-inch ring-shank nails) the top layer to the bottom, being careful not to puncture the vapor barrier. Finally, cover the plywood with 15-pound felt and install the flooring. To insulate the floor, a layer of compression-rated foam insulation can go between the poly vapor barrier and the plywood.
In general, the more nails in wood flooring, the less likely there is to be movement or squeaks. The recommended nailing schedule for 3/4-inch-thick strip flooring is every 8 to 10 inches with a 7d or 8d flooring nail (see Table 5-5). If the subfloor is less than 3/4-inch thick, nail into the joists with one nail between each joist. Stagger the ends of strip flooring at least 6 inches.
For plank flooring 4 inches and wider, the minimum nail spacing is 8 inches; closer is better.
With boards over 5 inches wide, if the ends are not end-matched (with T&G), the ends will tend to cup or curl unless face-nailed or screwed and plugged with two to three fasteners.
It is also a good idea to secure the flooring along its length with face-nails or screws and plugs.
If nailing, use wedge or screw-shank flooring nails set below the surface, or decorative nails left exposed for a traditional appearance.
Drive the face nails about 30 degrees away from the center to help reduce cupping. Use two to three nails across for planks up to 5 inches, three to four nails for planks up to 8 inches.
Details about our recommendations for finishing wood floors, including photos and tables are at FLOOR, WOOD FINISHES. Excerpts are below.
If possible, allow the home’s heating, ventilating, and air conditioning (HVAC) system to run for two weeks after the flooring is installed before sanding and finishing. The most common site-applied floor finish today is oil-based polyurethane, although waterborne urethanes are rapidly gaining market share due to their fast drying, low level of volatile organic compounds (VOCs), and non yellowing appearance (although “ambering” formulas are now available).
For those seeking a more rustic, lower-gloss appearance and willing to wax and buff periodically, traditional oil sealers and wax remain an option. Finishing options are summarized in Table 5-6.
These finishes are generally made from mixtures of linseed or tung oil, sometimes with synthetic polymers and additives to improve hardness and drying time. Usually two coats of a penetrating sealer are applied, followed by a coat of wax, providing a low-sheen, rustic appearance. While easy to apply, the finish is fairly high-maintenance, requiring periodic buffing and rewaxing to keep it looking good.
Over time, the wax will become discolored from dirt and grime and will need to be stripped. In its favor, high use areas of the floor are easy to touch up without sanding and refinishing the entire floor.
Most site-applied finishes today are oil-based or water-borne urethanes applied to the surface of the wood in three or more coats. In general, any high quality urethane applied properly will provide a durable, moisture-resistant surface.
While water-borne finishes had some quality problems when first introduced for residential use in the late 1980s, they have continually improved and now offer durability equal or superior to traditional oil-based urethanes. While most floor finishes claim in their marketing to be the toughest, hardest, and longest lasting, moisture-cured urethane is generally considered the toughest site-applied finish.
The most durable finishes, some with warranties of up to 25 years, are available only on factory-finished flooring.
Whatever finish is applied, follow the manufacturer’s instructions closely. The following recommendations apply to most site-applied finishes:
The main disadvantage of this approach is that the installer must take extra care not to mar or scratch the finishes during installation, adding to the installation cost.
Also, most prefinished flooring is chamfered to some degree to hide the inevitable differences in thickness from one board to the next, called overwood, which results from small variations in water absorption, swelling, and shrinking among flooring boards. Debris or irregularities in the subfloor can also cause an uneven surface.
The grooves in deeply beveled flooring tend to trap dirt and can cause problems when it is time to sand and refinish, particularly with stained flooring. Unless the bevels are sanded away, they are hard to strip and difficult to match, leaving dark lines in the refinished floor. One approach is to refinish before the old finish is completely worn through by just lightly abrading the surface prior to recoating or using one of the no-sand refinishing products.
To address these concerns, most flooring manufacturers now offer prefinished flooring products with no bevel (square edged) or nearly invisible “microbevels” that minimize the effects of a beveled edge.
A sealed and waxed floor typically needs rewaxing no more than once or twice a year to keep it looking good.
ith surface coatings, most manufacturers do not recommend waxing. If a surface-coated floor gets lightly scratched over time but has not worn through to bare wood, it can be recoated in most cases without complete re sanding. After thoroughly cleaning the floor with a non residue cleaner, rough up the old finish with steel wool, light sandpaper, or a sanding screen, then apply a new coat of finish. Many coating manufacturers now offer no-sand refinishing products as well, formulated to bond to the old finish without sanding.
No wood floor should be flooded with water during cleaning. Either use a dry mop or a wet mop that has been squeezed dry. Water can find its way between floor boards and through scratches, swell the wood, and undermine the finish.
Details about the properties of and installation of engineered wood floors, also referred to by some as wood laminate flooring, are found at FLOOR, WOOD ENGINEERED, LAMINATE, INSTALL. Excerpts are below.
The main advantage of engineered wood floors is dimensional stability. Because most engineered floors consist of cross-laminated plies of wood, they are less likely to swell, shrink, cup, or warp. This makes them the best choice for applications subject to wide changes in moisture levels— below grade, over radiant heating, or over concrete slabs with poor drainage or no vapor barrier.
Laminated floors are also the best choice for glue-down applications because of their inherent stability. Another advantage is that engineered wood floors do not require a beveled edge. Most have tight-fitting, square-edged joints.
Laminated floors come in a wide variety of sizes, from 1/4 to 3/4-inch thick. In general, the more plies a flooring has, the stronger and more stable it will be. Three plies is typical. Look for a top wear layer of at least 1/8-inch if the floor is to be sanded and refinished in the future.
Typical laminated floors can be sanded and refinished once or twice; the best, up to three or four times. The sanding thickness in some laminated flooring is nearly as thick as in traditional hardwood strip flooring, which although 3/4-inch thick, can be sanded down only about 1/4 inch (see Figure 5-11).
Longstrip flooring has several short pieces of strip flooring in the top ply to give the appearance of random length strip flooring. Single panels are as large as 8x96 inches (see Figure 5-12). It is used primarily in floating floors, but some products may also be nailed or glued.
Since each panel is two or three strips wide, the end joints of these strips line up at panel ends, unlike in a true strip floor. Single-strip products, on the other hand, are visually indistinguishable from a traditional strip floor.
Veneers may be either sliced or rotary cut. Rotary-cut veneers make better use of the tree with less waste, but sliced veneers are harder and less prone to denting. Also, look for interior veneers that are the same wood as the face veneer or at least as hard. Soft interior veneers make a weaker flooring that is more prone to denting.
Laminated wood floors can be nailed, stapled, or glued with mastic to any dry wood subfloor. Many can also be glued directly to dry concrete (see “Installing over Concrete,” page 168, for how to test dryness). If the concrete is below grade, check with the manufacturer to see if the product is guaranteed for that application. A floating floor may be a better choice for below-grade applications.
In general, glue-down products are 1/4- to 3/8-inch thick parquet tiles, strips, or planks. Strips or planks are generally less than 2 feet long, since longer pieces are too difficult to straighten with glue. The only solid wood flooring that is glued is parquet, which gains stability from the short pieces and different orientations of the grain.
As with unfinished flooring, the building should be closed in, with all wet work completed and dried, before installing engineered wood flooring. Make sure the concrete or subfloor is sufficiently dry and the indoor humidity level is close to the level it will be when the building is occupied. Keep the flooring materials packaged until installation.
Another option is to float the finish flooring. You can float a floor over virtually any stable substrate, including concrete, wood, smooth tile, or even short-nap carpet. With most floating floors, the T&G pieces are edge-glued to one another with PVA wood glue and installed over a thin layer of closed-cell, high-density foam and a vapor barrier.
A floating floor is more resilient underfoot than one glued to concrete, but feels less solid than a nailed or glued floor. Some manufacturers offer a harder premium foam underlayment, which is recommended for those seeking a more solid feel underfoot. Still, customers should be aware that a floating floor will feel different from a nailed or glued floor.
Installers must leave a 1/2-inch expansion gap around the edges of floating floors, typically hidden by baseboard, or use special T- or L-shaped moldings at door openings and other transitions to accommodate movement (Figure 5-13).
Existing door casings can be undercut to allow for movement. Restraining the flooring ends at doorways or the room perimeter can lead to open joints or buckling.
Because there are no mechanical fasteners to the substrate, floating floors rely on good quality flooring and a very flat slab or subfloor to produce a smooth, trouble-free floor. In shopping for the flooring, choose materials that are straight and uniform in thickness, fit together snugly, and lay flat with few visible gaps.
The subfloor should be level to within 1/8-inch over 10 feet. If necessary, shim low points with clean mason’s sand or felt or rosin paper layered in the low spots to create a tapered shim (do not use asphalt felt over radiant floors, however, to avoid fumes).
While floating floors cannot tolerate the heavy vibration caused by standard floor sanding equipment, most floating wood floors can be lightly sanded and refinished or coated with sandless finishes. Follow the manufacturer’s recommendations regarding refinishing.
No-glue longstrip flooring is available from Alloc, Inc. and BHK of America (see Buy Interior Finish Product Resources). Each company uses its own interlocking edge design to snap the 8x48-inch or 8x96-inch panels together in place of adhesive. These products were developed in Europe where people often take their floors with them when they move.
The Denmark-based company Junckers Hardwood Inc. manufactures the only solid-hardwood floating floor. The 6-foot-long strips are held together with special metal clips that snap in place on the underside of the floor (Figure 5-14).
The clips, along with adhesive at butt joints only, work together to create a strong monolithic floor with the appearance of traditional strip flooring but the ability to move with moisture and temperature changes, making it ideal for use over radiant slabs.
The 5-inch-wide boards are either a single plank in width or two strips dovetailed together. The 9/16 -inch product is guaranteed for two sandings, the 3/5-inch for seven.
A recent introduction to the flooring market, bamboo is not really a wood, but a type of grass that matures in three to five years on plantations, making it an environmentally friendly alternative to premium hardwoods. To make bamboo into flooring, thin strips are laminated to form planks from 3/8 to 3/4-inch thick.
The familiar nodes that separate bamboo stalks into short sections create darker cross markings, giving the product an attractive and unusual appearance. A more homogenous color is also available from some manufacturers by using laminated strands.
Engineered bamboo flooring is as hard as maple and more stable than oak, and comes either unfinished or prefinished with the same types of finishes as used on hardwood flooring.
Details about radiant-heat wood floor systems and best wood floor installation practices where a radiant heated floor is used are found at FLOOR, WOOD RADIANT HEAT. Excerpts are below.
Radiant heating is a challenging application for wood floors due to the high temperatures, excessive drying, and greater temperature cycling to which the wood and finish are subjected. Careful monitoring and control of the moisture levels of the flooring and structure at the time of installation are critical for success.
Also, because a 3/4-inch wood floor over 3/4-inch plywood has an R-value of almost 2, similar to plush carpeting, wood systems generally must run at higher water temperatures than tile or vinyl floors. Large area rugs make it more difficult for the heating engineer to design a system that will heat the room without overheating the flooring.
Wood flooring can be installed over radiant slabs, or over dry systems where the hydronic tubes are stapled directly to the subflooring (staple-up) or laid on top in grooved panels. Dry systems are more common in retrofits and generally require water 10°F to 20°F higher than thin slabs, leading to reduced efficiency, and often ruling out low-temperature heat sources like heat pumps or solar.
Also, with less thermal mass than slab-based systems, dry systems are more prone to temperature fluctuations. All systems are designed to heat floors to about 80°F. Floors heated above 85°F are uncomfortable for occupants and may be damaged from the heat.
With any approach, the radiant slab or subfloor must be dry prior to installation. With slab systems, run the heating system for at least a week, up to three weeks if necessary, to dry the slab to a moisture content of 8 to 12% before installing the subfloor.
The subfloor and hardwood floor should be acclimated to the average annual moisture levels for the region and be within 2 percentage points of each other (see “Acclimatization,” page 167). Flooring that is installed too wet can lead to shrinkage cracks; flooring installed too dry can lead to expansion problems or cupping in humid summer weather.
To steer clear of problems, also follow these recommendations:
Over traditional concrete radiant slabs at least 4 inches deep, use either a floating hardwood floor or install subflooring and nail on 3/4-inch strip flooring. The subflooring can consist of two layers of 1/2-inch plywood floating over the slab (see “Installing Over Concrete,” page 168), or a single-layer 3/4-inch subfloor nailed to the slab with powder-actuated fasteners. Because it is thicker, the floating subfloor (Figure 5-15) will take slightly longer to heat up, but it does not risk puncturing the hydronic tubing.
In wood-frame construction, use a minimum 1 1/2-inch-thick slab of Gyp-Crete® or lightweight concrete, which provides thermal mass for the radiant floor. Above the slab use a floating hardwood floor, or nail strip flooring to 3/4-inch sheathing installed over the lightweight concrete.
Fasten the sheathing to 2x4 sleepers placed 12 inches on-center, with the lightweight concrete and tubing in between (see Figure 5-15 shown above). A two-layer floating subfloor, as described above, is also an option for larger rooms where the subfloor will be heavy enough to stay solidly in place without nails.
There are a variety of dry radiant systems that install just under or over the subflooring, making them ideal for retrofits. The tubing is either stapled to the underside of the subflooring, laid over the joists (with spacers to fur up the sheathing), or placed over the subflooring in grooved plywood panels. Engineered wood floating floors are best with these systems, but nail-on hardwood flooring can work if installed with care.
Details and illustrations about selecting and installing resilient flooring, sheet vinyl, vinyl tiles, or cork floors are at FLOOR, RESILIENT VINYL or CORK. Excerpts are below.
Multi layer sheet vinyl is by far the most common material used in resilient floors. It comes in a variety of grades and a vast array of colors and patterns and, if installed well and maintained properly, should last 10 to 20 years. Solid vinyl tiles are another popular option; but, with multiple seams, they are more vulnerable to intrusions from water and dirt. Natural alternatives to vinyl that are growing in popularity include cork, in sheet or tile form, and old-fashioned linoleum, which is making a comeback in residential installations with new colors and marbleized patterns.
Sheet vinyl is manufactured to be either fully adhered to the substrate with mastic or bonded only at the edges, called a perimeter-bond system. Flex-type vinyl flooring, made for perimeter-bond installation, tolerates minor unevenness and movement in the substrate better than fully adhered systems, but fully adhered systems are more durable overall and less likely to be damaged from stresses like a heavy piece of furniture being dragged across.
All modern sheet vinyl flooring has three layers:
Better quality vinyl floors tend to be thicker overall and have a thicker and higher-quality wear layer. As the wear layer gets abraded from dirt and grime, it becomes duller and harder to clean. The thickness of the wear layer can range from 5 to 25 mils, and the flooring thickness from about 1/16-inch to 1/8-inch. Better quality products offer better resistance to stains and scratches than lower-end floors, and some of the top quality floors are guaranteed not to rip or permanently dent.
Similar to inlaid sheet vinyl, the color and pattern in solid vinyl tiles run through the full thickness of the tile, making them very durable. Because the color and pattern extend through the tile, they do not wear away with heavy use, but choices are limited. Solid vinyl tiles are cut from a solid block of material and come with a low-gloss finish.
One type, vinyl composition tile or VCT, is essentially the same product as solid vinyl, but with other binders and fillers. Both types require waxing and buffing, both to seal any gaps between tiles and to create an easy-to-clean surface.
Vinyl flooring can be installed over approved wood-based underlayments, dry concrete, or existing vinyl or linoleum if it is in good condition, clean, and free of wax or grease. However, any imperfection in the underlayment will telegraph through the finished floor, so if there are any questions, it is best to install new underlayment.
Most problems with vinyl are caused by problems with the underlayment, such as nail pops and swelling or delamination due to moisture. Adhesive failures at edges or seams can also be a problem.
To avoid these types of problems, use only underlayments and adhesives that are recommended by the flooring manufacturer. Also, if possible, avoid seams—most sheet vinyl comes in 6- and 12-foot rolls, so many rooms can be done without a seam. If seams are required, darker colors and textured pattern are preferable and help hide dirt and scuff marks as well. All seams should be sealed with an approved sealer to keep dirt out and to keep water from penetrating and undermining the adhesive bond.
If installing over a concrete slab, make sure it has a proper vapor barrier and has cured for at least 60 days. A concrete sealer is recommended. Existing slabs should be wire brushed, swept clean, and primed with an approved primer before gluing down resilient flooring.
Because vinyl shrinks and expands with room temperature, it should be allowed to adjust to the room temperature before installation. In general, the room should be heated or cooled to its normal temperature and the vinyl allowed to acclimate for 24 hours.
For a problem-free floor, sheet vinyl must be installed over a smooth, hard, and dry surface approved for use with vinyl.
Make sure the subflooring is dry before installing the underlayment. Use minimum1/4-inch-thick panels so that the underlayment plus subfloor is at least 1 inch thick. Stagger joints in the underlayment so they are offset from joints in the floor sheathing by at least 2 inches (see Figure 5-16).
Most flooring manufacturers specify a 3 1/2-inch gap between sheets, filled with a quick-setting latex-based cementitious filler. The filler restrains the edges of the underlayment and helps prevent ridging from movement or the absorption of flooring adhesive at panel edges.
The nailing schedule is shown in Table 5-7. Fasteners should approximately equal the thickness of the underlayment and subfloor and should not be driven into the framing.
Many contractors prefer staples to nails, because they do not leave dimples in the underlayment. Before using staples, however, make sure that they are approved by the resilient-flooring manufacturer. Nails should be ring-shank or spiral-shank and driven flush or just below the surface, but the heads should not be filled.
Other holes, gaps, and voids should be filled with a latex-based cementitious filling compound before laying the floor.
Homeowners who want a resilient floor covering but are looking for an alternative to vinyl should consider the new cork products as well as traditional linoleum, which is enjoying a comeback in residential applications.
Cork is a renewable resource that is harvested every 9 or 10 years from the outer bark layer of cork oak trees in Portugal and other Mediterranean countries. Cork has a number of desirable attributes for a flooring material: its air-filled, watertight cells are strong, soft to walk on, and insulating, making it a good choice over a concrete slab.
To make it into flooring, manufacturers grind up the cork, mix it with a chemical binder, bake the material, and slice it into sheets. Cork flooring products range in thickness from 3/16 to 7/16- inch for some laminated products.
Most cork flooring is sold as tiles and installed with adhesive, similarly to other resilient tiles. Tiles are available either unfinished or prefinished with carnauba wax or a more durable polyurethane or acrylic coating. Tiles tend to have natural color variation and can be purchased in light, medium, or dark tones.
As with wood floors, wax finishes need regular buffing and periodic rewaxing, depending on use. Polyurethane-finished cork typically needs recoating in four to eight years. One advantage of purchasing unfinished tiles and finishing in place is better protection against moisture penetration between tiles. The cork itself is moderately water-resistant.
A variety of other cork and cork composite products are now on the market, including tongue-and-groove (T&G) floating floors and cork and vinyl laminates.
A number of manufacturers now offer 12x36-inch floating T&G planks with an MDF core sandwiched between a cork underlayment and aggregate cork wear layer. Manufacturers include Korq, Inc., American Cork Products Company, and Nova Distinctive Floors, which offers a unique no-glue option.
Some manufacturers offer a composite product with an inner layer of cork sandwiched between a thick vinyl wear layer and vinyl backing (see Buy Interior Finish Product Resources).
While cork products appeal to healthy-house advocates, the binders and adhesives used with tiles, and the fiberboard or vinyl layers used in laminated products, may not provide the completely nontoxic, non-offgassing material desired. Using solid-cork (aggregate) tiles with a low-VOC adhesive is probably the best choice for those seeking natural, nontoxic materials.
For the last 50 years or so, linoleum has been used almost exclusively in commercial settings, but it is making a comeback in residential settings, due largely to its use of all-natural ingredients and reputation for durability. Linoleum is made by boiling oil to form a thick cement paste that is mixed with pine rosin, wood flour, and other fillers such as clay or limestone to make a durable, resilient sheet flooring that wears well and resists indentation.
The backing is typically jute fabric, a natural fiber. Other than relatively minor initial off-gassing from the linseed oil base, linoleum is considered nontoxic by most healthy-house advocates. It is also naturally antimicrobial and anti static, making it well suited for hospitals, schools, and rooms with electronic equipment. If well maintained, a linoleum floor can provide a 20- to 30-year service life.
In response to new demand for the product in recent years, manufacturers have responded with a wide variety of solid and marbleized colors and attractive checkered patterns, available in sheet form as well as 19x19-inch tiles that can be mixed to create borders and other designs. Unlike vinyl, linoleum colors go all the way through the product, making scratches and wear spots less noticeable than on vinyl. Also, scratches, cigarette burns, and other surface wear can be removed with steel wool or a nylon abrasive pad and buffed out.
However, since linoleum does not have a separate wear layer like vinyl flooring and is slightly porous, it requires somewhat more maintenance than vinyl. Applying a sealer or polish to the new floor will help it resist stains and make it easier to clean. Also, portions of a linoleum floor not exposed to light will tend to darken or yellow due to the natural oxidation of the linseed oil base. This coloration will disappear upon exposure to light, and the original linoleum color will be restored, or “bloom.”
All linoleum flooring is now manufactured in Europe. The largest supplier in the United States is European-based Forbo Linoleum, Inc., but U.S.-based flooring companies such as Armstrong are beginning to offer linoleum products as well. A unique floating linoleum plank floor that can be installed with or without glue is available from Nova Distinctive Floors.
Details and illustrations for Selecting & Installing Plastic Laminate Flooring are at FLOOR, LAMINATE PLASTIC. Excerpts are below.
Plastic laminate flooring was introduced to the U.S. market in the mid-1990s and now competes with vinyl as a low maintenance floor covering. Similar to the high-density plastic laminate used on countertops, the flooring is protected by a clear melamine layer, in some cases reinforced with aluminum oxide. A high-density fiberboard core provides stability and resilience, and a melamine layer on the bottom provides some protection against moisture.
The plastic laminate flooring product comes as either tiles that resemble stone or ceramic tiles or planks that simulate wood flooring. Both are floating products, edge-glued with PVA adhesive, but not attached to the subfloor. As with floating wood floors, a layer of1/4-inch-thick high-density foam goes under the floor to provide a cushion and even out small irregularities in the subfloor. Most manufacturers offer a higher density premium foam, which is recommended for a more solid feel underfoot.
If the product is installed properly, with sufficient glue to squeeze out along all joints, laminate flooring is moderately waterproof. The main problems occur at edges. To prevent water infiltration, seal with silicone any edges that might be exposed to water in kitchens, bathrooms, or other wet areas. Even with these safeguards, many manufacturers will not warranty laminate flooring in bathrooms. Radiant heat applications are generally acceptable.
In general, laminate flooring has a very hard surface that resists dents, scratches, and other damage. However, over time, high-traffic areas will lose their sheen and show signs of wear. Other than to replace the planks in those areas, there is little that can be done to restore the original finish.
Laminate flooring installs over a vapor barrier and thin layer of foam like floating wood floors (see “Floating Floors,” page 173). As with floating wood floors, the substrate must be very level. Fix any low spots with latex- or acrylic-based cementitious compound or building paper layered in progressively larger pieces.
Concrete must be dry enough that it will not fog a one foot square of polyurethane taped overnight. Thoroughly clean the slab or subfloor, and lay down the vapor barrier and foam provided by the laminate flooring manufacturer. Lap the vapor barrier 8 inches or tape the foam seams, if that is also serving as the vapor barrier, as allowed in some systems.
The tiles or planks are then glued together with a PVA glue provided by the manufacturer. Pieces are tapped into place and clamped with special strap clamps. Even squeeze out of glue along the entire glue line indicates sufficient glue, which is necessary for a solid, waterproof floor.
As with other floating floors, special T-shaped or L-shaped threshold, end, and transition moldings conceal the ends of flooring at transitions while allowing movement. A1/4-inch gap at the perimeter of the room is typically concealed by the baseboard or quarter-round molding nailed along the bottom of the baseboard (nailed only into the baseboard).
Details about choosing and installing wall-to-wall indoor carpeting are found at CARPETING, SELECTION & INSTALLATION. Excerpts are below.
Over 90% of the carpet installed in the United States is tufted, meaning that loops of yarn are stitched through a fabric backing, usually polypropylene, and glued in place with styrene-butadiene (SB) latex adhesive. This carpet is backed by a thick layer of SB latex or, in higher-end products, a secondary layer of fabric. The loops of yarn are either left in place for loop-style carpets, such as Berbers, or cut with blades for cut-pile carpet (Figure 5-17).
Traditional woven carpeting, representing only about 2% of U.S. production, is costly but creates a dimensionally stable and durable carpet including velvet, Axminster, and Wilton. With modern manufacturing techniques, however, nearly any style can be created using tufted construction. Common styles and their wear characteristics are shown in Table 5-8.
Nylon, considered the most durable synthetic carpet, accounts for about 60% of all pile carpeting. Most of the remaining are made of olefin and polyester, with wool accounting for less than 2% due to its high cost. Nylon is popular because of its good resilience (springs back rather than crushing) and overall durability (Table 5-9). Additives can give nylon good stain resistance.
Because olefin (polypropylene) is prone to crushing, it is generally used for low-pile designs, such as Berbers. Olefin is also widely used for indoor/outdoor carpeting used in high-moisture and recreational environments because of its resistance to moisture, mildew, and stains. Polyester carpeting is very soft to the touch but not as durable as the other synthetics.
Other than the material, the durability of a carpet depends on several factors: density of the tufts, twist of the yarn, and heat setting.
Density refers to how much yarn is used in the pile. The more tufts of yarn per square inch, the more yarn there is to wear and provide a resilient surface that resists crushing. The denser a carpet, the harder it is to push through the carpet to the backing with your fingers. Also, when bent back in a U-shape with the pile facing outward, a denser carpet will show less of the backing. Density is measured in stitches per inch or face weight, which is the weight of the fiber in the pile per square yard of carpet. When divided by the pile height, this gives the average density per inch of pile. These numbers are useful for comparing similar products that use the same materials, but otherwise can be misleading.
Twisting the yarn enhances the durability, particularly in cut-pile carpets. In most nylon, olefin, and polyester cut piles, the twist is set by heat or steam to help the carpet retain the twist. The cut ends of the carpet pile should be neat and tight.
Higher piles create a softer feel and more luxurious appearance but tend to crush more easily and are more difficult to clean.
Most carpeting today is very colorfast. Solution-dyed carpet, in which the dye is added to the fibers when they are made, is extremely colorfast. Yarndyed carpet, which is dyed after the yarn is made, provides some color variation and is also very colorfast. In general, light-colored carpets show dirt and stains, while dark colors show lint. Mottled colors such as tweeds and textured patterns tend to disguise dirt and wear, and are good choices for high-traffic areas and rooms where spills or stains are likely.
Many manufacturers rate the durability of their carpeting on a numeric scale or with descriptions such as low, medium, and high durability. These are a useful gauge of performance, but the proof is in the warranty. Look for a 7- to 10-year wear-and-stain warranty. Find out if the warranty is prorated or covers the full replacement cost. Also, read the fine print, as certain kinds of stains, such as pet stains, are often excluded.
By absorbing much of the impact of foot traffic, carpet padding helps prevent the carpet fibers from getting crushed and wearing out prematurely. The cushioning effect also makes the carpet more comfortable underfoot. Good padding is sufficiently firm and resilient to absorb foot traffic, and durable enough that it will not break down or collapse over time. Good padding also increases insulation and soundproofing and makes carpeting easier to vacuum by allowing air to circulate through the carpet.
For residential applications, pads should generally be no more than 1 7 6 inch thick for high piles and no more than 3 8 inch thick for Berbers or low piles. In general, softer, thicker pads are used in bedrooms, dens, and other rooms with light traffic. Thinner, firmer pads are recommended for living rooms, family rooms, hallways, stairs, and other high traffic areas. Berber-style carpets also require thinner, firmer cushions for support.
If too thick, the pad can cause too much flexing in the carpet, weakening the backing and opening seams. A carpet pad that collapses, or starts out too thin, can cause carpeting to wrinkle or wear out quickly. Seams in the pad should run perpendicular to the carpet seams or be offset by at least 6 inches.
Prime urethane pads are the least expensive, but have a tendency to compress with use, particularly in high-traffic areas. As the pad compresses, the carpet backing can break down from too much flexing. For that reason, prime urethane pads are not recommended for carpeting subject to moderate or heavy traffic. One exception is a proprietary urethane called Omalon (E. R. Carpenter Co.), which has a special cell structure that resists crushing and is guaranteed for the life of the carpet.
Bonded or re bonded pads, made of multicolored scraps of high-density polyurethane foam bonded together, are the most common in residential construction. The denser the foam, the better the feel underfoot and the durability. The Carpet and Rug Institute (CRI) recommends that rebond be a minimum of 5 pounds per cubic foot and 3/8 inch thick for light-traffic areas, such as a bedroom, and 6.5 pounds and 3/8 inch thick for heavy-traffic areas, such as hallways. For longer wear in high-traffic areas, use a 7- to 8-pound rebound. For a more plush feeling, choose a7/16-inch thickness.
Natural and synthetic fiber pads are sometimes used under area rugs, commercial carpets, and some Berber carpets. They are made of jute or recycled synthetic carpet fiber and are among the densest and most resilient pads. Synthetic fiber pads are the best choice for potentially damp concrete floors. With synthetic fiber pads, look for a minimum density of 7.5 pounds per cubic foot or 12 pounds for jute. The thickness should range from 3/8 to 7/16- inch.
Some Berber carpets require special padding. In general, the bigger the loop in the Berber, the firmer the padding should be. Woven carpet may also require special padding, typically an extra-dense fiber pad or, in some cases, a heavy frothed foam.
Stretch-in installations using tack strips along the room perimeter are the most common approach in residential carpeting. Glue-down installations are primarily used in commercial work but are used residentially over slab-on-grade and in basements.
Glue-down installations can either use carpeting with an attached cushion backing or the “double-glue” method in which the pad is glued to both the concrete and the carpet. For installations over concrete, the concrete should be fully cured and surface free of dirt, dust, and any curing agents.
A good carpet installation starts with a properly prepared subfloor. The minimum recommended subfloor is 3 4 inch T&G plywood, nailed and glued. For a higher quality job, an 1/4-to 3 8-inch underlayment should be installed over the plywood with the seams offset from the subfloor. Follow the underlayment specifications for resilient flooring, discussed above. Check for loose or squeaky spots and nail with spiral or ring-shank nails before installing the carpet.
For a level transition, the top of the underlayment should sit about 1 2 inch below the finished height of adjacent solid flooring materials, such as wood, tile, or resilient flooring.
Carpet and pad can also go over hardwood floors or tightly glued resilient flooring. Repair any loose areas or damage in the existing flooring before installing the pad and carpet.
Most residential carpeting in the United States is available in either 12- or 15-foot-wide rolls, but the installer needs a few inches of waste on each end for stretching installations, limiting the size of a room that can be done with no seams.
Since all seams are visible to some extent, they should be placed where they are the least visible and get limited traffic, such as inside of closets. Seams should always run with the pile in the same direction. Where a room is lighted from windows, the seams should go perpendicular to the windows. In hallways, place any seams along the length of the hall. If a seam must be between rooms, make sure it is hidden when the door is closed. As the fibers are compressed from wear over time, seams become more conspicuous.
Seams are easiest to conceal in deep, dense, cut-pile carpeting.With short loop-pile carpets, such as Berbers and other loop-pile carpets with heavy textures and irregular rows of tufts, it can be difficult to hide seams. Also carpets with pads hide seams better than glue-down installations. Where seaming problems are anticipated, use wider 6-inch hot-melt tape at seams rather than the standard 3-inch tape. The wider tape helps avoid a high spot at the seam.
To avoid problems with wrinkling, carpeting should be warmed up to the normal room temperature for about 24 hours before it is installed. This can take place in the home or in a heated warehouse. The building should also be heated to normal temperatures before and during the installation and be free of excess moisture. If the carpet is installed cold, it can expand and wrinkle when heated to normal conditions.
Wrinkling and ridging at seams can also result from carpeting that is not adequately stretched during installation. While manual stretching was adequate for older carpeting with natural jute backing, the polypropylene backing used today requires the greater force of power stretching. In fact, many manufacturers will not warrant their carpet on rooms larger than 12x12 feet unless it is power stretched.
The stretched carpet is held in place with tack strips nailed around the perimeter of the room about 1 2 inch in from the baseboard. Standard 1-inch-wide tack strips are adequate for most carpeting, but some heavy woven and Berber-style carpets require 2-inch strips (or two 1-inch strips) to hold them securely in place.
In recent years, a number of homeowners and advocacy groups have attributed a variety of health problems to exposure to new carpeting. Although studies have been inconclusive, the carpeting industry has taken steps to reduce exposures of certain chemicals and has established a certification program for low-emitting carpets. For more information, see the section on “Carpeting,” page 292).
Details and illustrations about selecting and installing interior trim in buildings are found at TRIM, INTERIOR INSTALLATION. Excerpts are below.
Once the domain of premium softwoods, such as clear pine, poplar, and other easily machined woods, interior trim is just as likely now to contain a mix of finger-jointed stock, medium density fiberboard (MDF) molded urethane for decorative trim, and flexible polyester moldings that must bend around curved surfaces.
Wood moldings and other finish lumber are graded for visual properties only. In general, the higher the grade, the more uniform the grain and color will be, and the fewer the defects, such as small knots, pitch pockets, and other natural markings. In some species, there is also a marked color difference between heartwood and sapwood. Some customers might like the natural variation found in lower grades; others find it objectionable.
Most lumberyards stock only a few molding profiles in pine and even fewer in hardwoods. Specialty molding suppliers, however, offer a far wider variety of stock profiles in both softwoods and common hardwoods. Molding suppliers also stock a variety of architectural ornaments, such as rosettes and plinth blocks, that can dress up a job or match a traditional style without the cost of custom millwork.
Most wide, flat moldings are recessed or “backed out” a little to reduce the tendency to cup. Cutting kerfs in the back of flat board stock will accomplish the same effect (see Figure 5-18).
While some lumberyards stock small quantities of milled hardwood boards and a few molding profiles, most larger jobs require the purchase of rough stock from a hardwood supplier or millwork shop. Hardwood trim characteristics are shown in Table 5-10.
If a job requires all clear stock that is “color matched” with minimal color variation from board to board, you will probably need to purchase the highest grade available, often FAS (firsts and seconds), and may still need to cull some pieces. For jobs where more grain variation is acceptable, No. 1 Common or No. 2 and 3 Common may suffice. FAS is at least 80% clear stock with minimum boards 6 inches wide by 8 to 16 feet long. No. 1 is at least 65% clear with narrower boards, and No. 2 and No. 3 are 50% and 33% clear, respectively.
Providing the shop with a specific cut list of finished pieces is the best way to guarantee that they deliver the pieces needed for the job. For a premium, you can obtain all-heartwood, all-sapwood, or color-matched boards for uniform color in glue-up work and throughout the job. Also, the millwork shop can plane the stock on one or both sides, joint one or both edges, and sand one or both faces as needed. Generally, the millwork shop can dress the boards far more economically than a contractor can in the field or in a small shop.
A job with hardwood trim may also require profiled moldings, such as baseboard, chair rail, or crown. Custom hardwood moldings require a substantial lead time and a setup fee to make the cutter knives. Many shops keep cutters on hand for standard profiles, as well as custom profiles from prior jobs. Using an existing cutter can significantly cut costs and lead time.
Finger-jointed stock is widely used for paint-grade door and window jambs, as well as profiled moldings. Finger-jointed stock generally performs well, but in some cases, joints between the individual pieces will “telegraph” through the painted finish due to minute differences in the swelling and shrinking of the individual pieces of wood. To avoid this problem, sand any uneven joints before applying any finish. Also, back-priming the material will reduce any moisture movement after installation, minimizing problems with telegraphing.
Medium-density fiberboard (MDF) is a fine-grained composite material made from wood particles and resin bonded under heat and pressure. The resin is generally urea-formaldehyde, a known lung irritant, but a few manufacturers offer alternative products made with the more stable phenol formaldehyde or other low-emission resins. SierraPine Composite Solutions makes Medex, a moisture-resistant MDF product, and Medite II, an interior panel, both using a formaldehyde free resin called MDI (methylene diisocyanate).
In many markets, MDF has become the material of choice for trim and casework due to its low cost, ease of machining, and excellent appearance when painted. It is uniform in consistency and dimensionally stable. MDF trim is available preprimed in a number of standard molding profiles, and 4x8 MDF panels are easy to cut to size and can be routed or shaped to a clean, crisp profile. However, a 3/4-inch 4x8 panel weighs 95 pounds versus 75 pounds for birch plywood, making MDF sheets a challenge to maneuver.
While MDF offers many benefits, it is not problem free. Cutting and milling creates a super fine dust, which requires workers to wear tight-fitting respirators. Shops should have a good dust-extraction system as well. The urea-formaldehyde makes the dust more irritating to eyes and lungs and off-gasses to some extent after installation, making the product unacceptable to some (see Chapter 7, “Formaldehyde,” page 287).
Because of hardness, MDF moldings must be installed with pneumatic nailers, which tend to pucker the material around the nail. These “mushrooms” must be chiseled off prior to filling the nail holes.And although it holds paint well, cut and routed edges of MDF will absorb water-based primer and swell. To avoid these problems, edges should be sealed with a shellac-based or oil-based primer or painted with special finishes formulated for use with MDF. Due to its potential for absorption at edges, MDF is not a good choice for wet areas. Edge nailing is also not recommended, so MDF is not well suited to applications such as jamb extensions.
Although pricey, polyurethane foam moldings (also called polymer moldings) are popular for ornate decorative work. The leading manufacturer, Fypon, makes a wide range of large crown and cornice moldings, as well as architectural ornaments for mantles, decorative ceilings, and other decorative elements.
Urethane foam moldings are sold preprimed, and they can be cut, planed, and sanded like wood—only more easily because of their lighter weight. The moldings are installed with proprietary caulk or adhesive rather than nails, although a few finish nails are often used to hold them in place while the glue dries. Butt joints and miters are bonded with the same adhesive. Larger moldings are limited in length to 10 to 12 feet, requiring multiple joints on long runs.
Flexible moldings made from dense polyester resin have been available since the late 1960s, but they have improved a lot in recent years. Newer formulations are easier to nail, more resistant to cracking, and come in a wide variety of profiles, in both paint and stain grades (Figure 5-19).
Most manufacturers offer thinner profiles and softer formulations for tighter curves, as well as fire-retardant formulations. Less expensive rigid versions are also available for straight runs. While originally developed for interior use, many of these products are suitable for exterior applications as well.
The stain-grade material has an embossed grain, but must be stained after installation due to the stretching of the surface and requires a heavy pigmented oil-based or gel-type stain with a clear topcoat.
Most flexible moldings are made to order and can perfectly match typical finger-jointed or MDF profiles if specified correctly when ordered—manufacturers have thousands of molds matched to various manufacturers’ stock moldings. Simple curves such as baseboard or chair rails generally do not need pre forming, but crowns, arch top casings, and most small-radius curves must be preformed by the manufacturer for the specific radius needed. Manufacturers can accommodate ovals, ellipses, and other irregular curves if provided with accurate design specs.
The material cuts easily with standard woodworking tools, but it needs to be held in a jig or sandwiched between wood blocks for difficult cuts. Most manufacturers recommend installation with construction adhesive, panel adhesive, or gel-type super glue, with a few finish nails to hold the molding in place while the glue dries. Pneumatic pin nailers work well. However, nailing too close to the edge may distort or crack the rubber material. Large moldings such as crown need wood backing or triangular blocks to prevent the molding from bowing in. (see Buy Interior Finish Product Resources for a list of suppliers.)
Details about building shelving and other casework are at CASEWORK, CABINETS, SHELVING INSTALLATION. Excerpts are below.
For shelving, built-ins, and other casework, contractors can choose from a wide array of panel products. The most widely used are veneer-core plywood, MDF, and particleboard. MDF and particleboard are available either unfinished or with a wood veneer or melamine facing. Medium density overlay (MDO) is a good option for cabinets exposed to very high humidity or exterior uses.
Cabinet-grade plywood typically has five inner plies (more for better grades), plus the face veneers, and in most cases uses phenol-formaldehyde adhesive, which has negligible off-gassing. Plywood is strong and dimensionally stable. For paint-grade cabinets, birch plywood remains an excellent choice.
Baltic birch plywood uses all birch for the inner plies, is free of voids, and can be edge sanded, making it ideal for drawer sides and similar applications. For stain-grade work, hardwood plywood can be special ordered with matched veneers. Where screwing into edges is required, 7-ply material is less likely to split.
Medium-density fiberboard is a fine composite material made from fine wood fibers and resin, usually urea-formaldehyde (see description on page 184). MDF is available as both a paint-grade panel or faced with wood veneer or melamine.
Because of its competitive pricing and good workability, MDF is now the dominant panel product in many markets. In paint-grade work, the edges need to be sealed or banded due to high absorption of paint. Concerns about off-gassing of formaldehyde could be a concern to customers with allergies or chemical sensitivities.
However, if laminated on all faces with an impervious facing, such as melamine, or finished with two or more coats of varnish or an oil-based paint (or paint rated as a vapor barrier) on all faces, the off-gassing will be minimized.
Particleboard is similar to MDF, but with larger fibers, so it doesn’t machine to a crisp edge and leaves a noticeable texture when painted. Also, edges and corners are more prone to chipping than with MDF. Like MDF, it off-gasses urea-formaldehyde. Sealing all surfaces will minimize the problem.
Medium-density overlay is an exterior grade plywood with a durable resin-treated paper facing that takes paint exceptionally well. It is widely used for sign making as well as concrete forms. Though not typically used in casework, it is an ideal material for cabinets that will be exposed to extreme moisture or exposed to weather on porches, patios, or other outdoor locations.
Typical shelf spans for simple shelves sitting on cleats at both ends are shown in Table 5-11. These assume a load of heavy books and minimal deflection, although long-term deflection under a constant load may be greater. To stiffen shelving, it can be supported along the back edge or reinforced in front with solid-wood facing, glued and nailed in place. For example, a 1 1/4-inch solid-wood apron along the front edge will increase the span for plywood shelving to about 36 inches.
Details about how to select an interior door, the types of doors and their properties, and how to install them are found at DOORS, INTERIOR. Excerpts are below.
Over 90% of interior doors today are either flush or molded. In either case, a facing of wood veneer or hardboard is glued to a core, providing the door with its strength. Traditional rail-and-style construction is still used, primarily for stain grade work, although composites and veneered construction are widely used with this type of door as well.
These are the most expensive doors and are used mostly for stain-grade work. They gain their stability by allowing the flat or raised panels to float in the frame without increasing the door’s overall width (see Figure 5-20). Rails and stiles are typically dowelled and glued to make a rigid connection at corners.
For both cost saving and increased dimensional stability, many doors now use composite materials. Rails and stiles may have a wood veneer over a core of finger-jointed wood, particleboard, or MDF. Other doors build each rail and stile from a solid strip of appearance-grade solid wood sliced in half, reversed upon itself, and reglued so the opposing grain patterns help resist warping.
On paint-grade doors, the raised or flat panels are often MDF, which does not move with humidity changes or leave an unpainted strip when the panels shrink. If painting doors with solid wood panels, order them preprimed to help reduce problems with the paint line.
On stain-grade doors, the panels are either solid wood or veneered MDF, which offers greater dimensional stability and the appearance of solid wood to all but the most discerning eye.
The standard choice for modern homes in the 1950s and 1960s, flush doors have a 1 8-inch wood or composite veneer glued to either a solid or hollow-core frame. Molded doors are constructed the same way, but with a hardboard facing molded to simulate a frame-and-panel wood door.
All flush and molded doors have solid rails and stiles and a solid area (the lock block) where the lockset is installed. The rails and stiles are either solid wood, fingerjointed stock, or MDF in lower-end doors. Wood stiles may be combined with MDF or particleboard rails to save money. MDF stiles may not perform well in bathrooms or wet areas due to their tendency to absorb moisture.
A corrugated cardboard grid fills in between the rails and stiles and keeps the facings rigid on a hollowcore door. The lock block where the lock set is drilled may be solid wood, particleboard, or MDF. The rails and stiles are often wider than on solid-core doors to provide structural stability. Despite their light weight, hollow-core doors are dimensionally stable and problem-free as long as the installer does not remove too much material during installation.
In residential doors, the rails and stiles are typically not fastened to one another or to the core material, but are held together by the wood or hardboard facing. The core is typically particleboard, MDF, or low-density fiberboard, which reduces the weight by about 25%.
A standard 2'6"x6'8" hollow-core flush door weighs about 30 pounds versus 75 to 80 pounds for a solid-core version. The price difference is modest, but most homeowners prefer the solid feel and better sound blocking of a solid-core door. However, the extra weight can put a strain on MDF jambs, which are now finding their way onto job sites. Driving one long hinge-screw into the framing at each hinge will help avoid problems.
A molded door is built like a flush door, except the hardboard facing is molded to simulate the appearance of a traditional frame-and-panel door. Most are available with an embossed wood grain. As with a flush door, the core may be either hollow or solid. How well the molded surface simulates a wood panel door varies from one manufacturer to another. Look for a product with crisp, well-defined details at the panels and molded edges around them, called sticking. The solid-core version also feels like a solid wood door when operated and provides better sound blocking than a hollow model.
Trimming too deep into a door’s stiles or outer rails can destroy its structural integrity. How much material can be safely trimmed depends on the specific door, so pay attention to the manufacturers’ recommendations. As a general rule, do not cut more than 3 4 inch off the top or bottom rails of traditional frame and panel doors, although some doors can be trimmed by 2 or more inches on the bottom rail.
With flush or molded doors, how much can be trimmed depends upon the width of the rails and stiles and, with solid-core doors, whether they are glued to the core material. With doors that comply with WDMA (Window and Door Manufacturers Association) specs, follow the minimum widths in Table 5-12.
With laminated doors, look for products in compliance with the WDMA Standard I.S.1-87. Under this standard, door samples must withstand multiple wetting and drying cycles without significant delamination. Products in compliance typically carry a one- to five-year warranty against delamination. Most warranties also cover any warping and twisting in excess of 1/4 inch across the length or width of the door but require that the door be sealed on all six edges. Oversized doors may have more limited protection against warping.
Details about the selection and application of interiot stains and finishes are at STAINS & FINISHES, INTERIOR. Excerpts are below.
Finishing stain-grade trim is equal parts art and science. There are a wide range of products and application techniques. With all finishes, careful prep work and control of dust on the job site are critical for a professional quality finish.
Starting with coarse grits and working to finer grits, sand all cabinets, doors, and other woodwork to remove any milling marks or chatter, scratches, dirt, or other imperfections. Highly visible surfaces like cabinets and doors should be taken down to a 180 or 220 grit. Use a dusting brush to clean off any visible dust between sandings, and thoroughly clean up after the final sanding. With solvent-based finishes, use a tack cloth to remove any residual fine dust.
With open-grain woods, such as oak, ash, mahogany, and walnut, it may take many coats of clear finish to fill the wood pores and achieve a glassy, smooth surface. Where a premium finish is desired, one approach is to apply a paste filler to the sanded wood, which is a thick, paste like varnish with finely ground quartz or talc to add bulk, and usually a pigment as well to match the wood tone. It is typically applied with a rag and sanded clean the following day. If using a filler that is darker than the wood, first seal the wood with a sanding sealer or thinned coat of the clear finish to keep the wood from being overly darkened. Generally, stains are applied after the filler has been applied and sanded.
Water-based stains and finishes tend to raise the wood grain when applied, creating a rough surface. The best way to avoid problems later is to intentionally raise the grain and sand it down before applying the finish. To accomplish this, after sanding the work, wet the wood surface with a sponge or cloth, and allow to dry overnight. Then knock down the raised grain with 180 to 220 grit sandpaper.
With some of the newer water-based formulations, this step may not be required. Instead, a light sanding after the first coat may be all that is needed. Whatever approach is taken to sanding, never use steel wool with water-based finishes, as leftover steel particles can rust and stain the work. Also, do not use a solvent-type tack cloth with water-based finishes, as the solvent residue can interfere with the finish. A clean cloth lightly misted with water can be used to remove any dust or sanding residue.
Stains for interior trim are either pigmented stains or penetrating dyes. Many ready-made stains at the lumberyard combine both pigments and penetrating dyes. The penetrating dyes work for the small-pore areas and the pigments add contrast to the larger pores.
Oil-based pigmented stains tend to highlight distinctive grain patterns, particularly in wood with large pores, such as oak and ash, but they also highlight any scratches or defects in the wood. Wood with uneven absorption will look blotchy. Also, because the pigments are large, opaque particles, they tend to act like watered down paints, obscuring the wood itself.
Dyes, which must be mixed by the applicator, are very transparent and tend to get absorbed equally into the wood surface, resulting in a more uniform color. They tend to give the wood an even, transparent color while letting the grain pattern show through. Over time, they will fade from exposure to natural light. Dyes are either dissolved in a water or oil solution and must be precisely mixed to obtain controlled colors.
Softwoods, like pine, and light-colored hardwoods, such as maple or birch, tend to absorb stain unevenly, so they benefit from sealing prior to staining. Depending on the desired appearance, you can use a shellac based sealer with a pigmented stain, obscuring the underlying wood, or a pre stain sealer with a penetrating stain. Pre stain sealers allow stain to penetrate the wood surface but with more even absorption. Pre stain sealers can also be useful when staining birch veneer, which tends to absorb stain unevenly, creating a blotchy appearance.
Stains and dyes may be oil, alcohol, or water-based. They may be applied with a sprayer, brush, roller, or rag and are typically applied to the surface, allowed to sit, then wiped off. Whatever type of stain is used, it should be completely dry before application of the clear topcoat. If using a water-based topcoat, check for compatibility with oil-based stains. Using a stain and clear finish from the same manufacturer will help guard against compatibility problems.
The best clear finish depends on the look desired, hardness required, and whether it must resist water (Table 5-13). Some finishes are best sprayed on, but most may be brush applied. Oil-based finishes are generally wiped on with a rag and create a low-luster, hand-rubbed appearance, but provide the least protection.
With most surface finishes, it is best to lightly abrade the finish between coats with 220-grit paper or No. 00 steel wool to increase the bond between coats. After sanding, wipe with a tack cloth for oil- or solvent-based finishes and a water-dampened cloth for water-based finishes. Most professional painters apply three to four coats of clear finish.
Because of its stiffness, wood framing readily transmits low-frequency sounds and impact noises through wood frame houses. This is particularly a problem in floors and walls separating two housing units, but it can also be an issue within a single-family home. For example, a person with a home office or music room might want to isolate it acoustically from the surrounding rooms so meetings or music proceed in private and so outside noises will not intrude. Bedrooms located under living spaces can also require special treatment to reduce impact noises from above.
Another kind of noise control is important where a house sits by a highway or under a flight path. The goal here is to keep outdoor noises from entering the house by reducing sound transmission through windows, doors, and exterior walls and ceilings. Special acoustical windows rated for low sound transmission are often required for substantial Reduction s in outside noise.
Sound can travel through both air (airborne sound) and solid materials (structure-borne sound). Structure-borne sound can be directly imparted to the building structure by a vibration, such as a humming compressor, or by direct impact, such as a boot stepping on a hardwood floor. As sound energy travels through a building, it changes from one type of transmission to the other and back, losing energy in each transition. Because of its rigidity, wood framing is a very good transmitter of low-frequency sound and hollow wall cavities and thin doors do little to reduce sound transmission.
Sound levels are measured in decibels (dB), which are on a logarithmic scale. A sound increase of just 10 dB indicates an increase of ten times the intensity, although our subjective experience is that the sound is twice as loud. Decibel levels for common sounds are shown in Table 5-14. Continuous exposure to sounds above about 85 dB can cause hearing loss in most people.
Sounds in an acoustically “live” room with all hard surfaces will seem loud and harsh due to the sound reverberating off the hard surfaces. Adding sound-absorptive materials, such as carpeting and soft furniture, will make sound softer and more pleasant within the room, but will do little to reduce the transmission of sound to adjacent rooms. To reduce transmission requires sound isolation strategies, typically using high mass materials, double-framed walls, or resilient connections between the drywall and framing.
To keep airborne sound from passing through walls and floors, there are four main strategies:
A cavity with fiberglass is far more effective at blocking sound if the two wall surfaces (or ceiling and floor surfaces) are mechanically decoupled as in a double-stud or staggered-stud wall. Resilient channel works essentially the same way by breaking the vibration path from the stud or ceiling joist to the drywall.
The hardest sounds to block are low frequency, such as the thumping of a stereo bass. Using decoupled construction, such as double walls or resilient channels, is effective. Where that is impractical, adding mass can also be effective. Very massive, non rigid materials such as lead or sand are ideal, but doubling or tripling the drywall is also helpful.
Sound takes the path of least resistance between rooms, through any air leaks or through rigid connections in the structure itself. These routes that bypass efforts at sound insulation are called flanking paths. These can significantly reduce the effectiveness of soundproofing efforts. Building walls with high STC ratings will do little good if sound can pass easily though electrical outlets or a thin, loosely fitting door. For example, an un gasketed door or the equivalent of a one-inch-square hole in a wall can reduce an STC 50 wall to STC 30. Common flanking paths include:
Addressing obvious flanking paths is often the most cost effective step in soundproofing a home. Strategies such as sealing air leaks between rooms, upgrading doors, and adding weather-stripping may provide adequate sound isolation without the need for more exotic and expensive measures.
How effectively a wall or floor reduces airborne sound is measured by STC ratings (sound transmission class). Roughly speaking, the STC rating equals the Reduction in decibel levels across the partition. So, for example, a 50 dB noise on the other side of an STC 35 wall will sound like a 15 dB noise to the average listener (see Table 5-15). Walls and floors in the field often measure lower than in laboratory ratings due to variations in workmanship as well as leaks and bypasses. The higher the STC rating, the more likely it is to be compromised by site conditions. For that reason, it is best to select a building assembly rated at least 5 points above the design goal.
In single-stud walls, the most cost-effective upgrade is to double the drywall on one side and add insulation to the cavity, increasing the STC from 33 to 40 (see Table 5-16). The joints on the second layer of drywall should not line up with the first layer.
To achieve substantially higher STC ratings requires adding a resilient channel to one side of the wall or decoupling the two sides of a wall with double framing. With no rigid connection bridging the two sides of the wall, sound transmission is significantly reduced. Decoupling and also increasing mass, such as doubling the drywall layers, will help cut transmission of low-frequency sounds as well.
For higher STC values required for special situations, such as a music room or home office, additional upgrades include increasing the mass on either side of the cavity, enlarging the cavity, or adding fiberglass batts or other sound-absorbing materials. Filling the gap more than three quarters of its width with insulation provides little additional benefit. In fact, stuffing the cavity too tightly could reduce the benefit of the fibrous insulation by creating a solid bridge. In general, polystyrene and other closed-cell insulations are poor sound absorbers and provide little benefit.
In general, doors should be within 10 STC points of the surrounding wall. Solid-core doors are recommended for bedrooms and bathrooms. Where higher-level sound isolation is required, you will need to add high-quality gasket-type weather-stripping and a sealed threshold. Also the gap between the door jamb and studs should be caulked or grouted to avoid sound leaks around the door.
For even higher ratings, which might be needed for a music room, for example, double doors are required (see Table 5-17).
For party walls between adjacent living units, STC ratings should be a minimum of 50. Recommended STC levels between bedrooms and adjacent rooms in single family homes and apartments are shown in Table 5-18. Where privacy and quiet are of concern to clients, a minimum STC rating of 45 is a reasonable target for bedroom and bathroom partitions. Closets along a wall can help buffer sounds as long as doors are not louvered.
The STC rating of a floor measures only the Reduction in airborne sound transmission. A floor, however, also transmits structure-borne sound, such as footsteps or a slammed door, directly through the materials. The ability to reduce impact sound is rated by the Impact Isolation Class (IIC) rating. The most cost-effective technique to reduce impact noise is to add a carpet and pad. For example, adding a carpet and pad to a conventional plywood subfloor over a gypsum ceiling increases the IIC rating from 37 to 65. By comparison, it increases the STC rating by only 4 points.
Where higher STC and IIC ratings are needed, a resilient channel can be added to the ceiling below. Where this is not possible, for example when the joists are exposed below, you can use a floating floor over a layer of soundboard or a high-mass floor over a layer of sand or lightweight concrete (see Table 5-19).
IIC levels are of greatest concern in stacked multifamily dwellings or in a single-family dwelling with bedrooms below other living spaces. Acoustical experts recommend a minimum IIC rating of 50 to 55 in ceiling/floor construction, separating living units in multifamily construction. HUD recommendations for bedrooms under living spaces are shown in Table 5-20. While these recommendations were developed for multifamily dwellings, they provide reasonable targets for single-family homes where sound privacy is desired.
One of the most common noise complaints in single-family construction is the sound of water gushing through PVC waste pipes. The best solution, short of using cast iron, is to box in the pipes and fill the cavity with fiberglass insulation. Then enclose the cavity with one or two layers of drywall.
Water supply and heating pipes can also radiate noise through the framing if there is rigid contact between pipes and framing or finish materials. This can be a particular problem when heating pipes expand and contract. To avoid these problems, make sure pipe runs are not tight against framing. Soundproofing Materials and Workmanship Like weatherization work, effective soundproofing requires careful detailing and workmanship. Small holes and bypasses can lower field STC values to 15 to 20 points below laboratory values. Leaky edge joints, unsealed doorways, interconnecting ductwork, and unsealed electrical and plumbing penetrations all degrade acoustical performance.
While special non hardening acoustical sealants are often specified in commercial work, any high-quality sealant that remains flexible can be effective in blocking sound transmission. Butyl, silicone, and urethane caulk can all be used. To prevent sound leaks, use sealant around electrical boxes, plumbing penetrations, and any other penetrations in the wall or ceiling surface. For walls with STC ratings in excess of 35, apply a flexible sealant at the joint where the drywall meets the floor. Acoustical sealant is also used to seal around the perimeter of walls or ceilings hung from resilient channel.
Resilient channel is installed perpendicular to the studs or joists and needs at least 3 inches of free space in the cavity behind it to be effective. It is not effective if attached to sheet materials, such as drywall. It is also important to use the right length screws, so they do not penetrate into the wood framing. Just a few screws into the wood can undermine the resilient connection and substantially lower the STC and IIC ratings. Leave a 1/4-to 1/2-inch gap around the perimeter of a ceiling or wall hung from resilient channel and fill with an acoustical or other non hardening sealant.
Ordinary fiberglass insulation is an effective sound absorber in cavities and increases the STC rating of walls by 3 to 5 decibels. The insulation needs to fill only about three-quarters of the thickness of the cavity to be effective. Adding more adds little additional sound protection, and stuffing insulation in too densely could actually increase sound transmission. Cellulose insulation has about the same sound deadening characteristics as fiberglass. Foam insulation is not particularly effective for sound control. Foam is too light to add mass to the wall and is not resilient enough to absorb sound.
Flexible, heavy rubber gasketing makes an effective seal against sound leaks as well as thermal leaks around doors and windows. Either bulb- or magnetic-type weather-stripping is effective as long as it makes an airtight seal between the frame and door or window. Duct Insulation. Use fiberglass ductboard or fiberglass duct liners to quiet the noises of fans and moving air. Avoid sharing a common duct between two rooms that need sound privacy.
Details, tables, and illustrations describing the selection of and standards for interior lighting are found at LIGHTING, INTERIOR GUIDE. Excerpts are below.
With the exception of purely decorative lighting fixtures, all lighting fits into one of three main categories: ambient, task, and accent. Most rooms use a mixture of lighting types to create visual interest and to meet the functional needs of the space. A space lit only by indirect light sources can seem visually flat, while a space lit only by directed light from spots and floods can seem harsh and cast dark shadows.
Similarly, a space lit only by accent lighting can look like an art museum and leave people in the dark. A balanced combination of strategies works best.
Ambient lighting is the general background illumination that is bright enough to allow people to move about safely and perform simple tasks. Ambient lighting can be achieved by directly lighting the lower part of the room (direct lighting), or by reflecting light off the ceiling and upper half of the room (indirect lighting).
Reflecting light upward off the ceiling and upper walls tends to give a room a spacious feeling and soften shadows on objects and faces. It can be achieved with built-in coves, wall sconces, and pendants that direct light upward, or freestanding torchiere-style floor lamps.
Lighting just the lower part of the room can create a more intimate feeling. Options include recessed lights and wall and ceiling fixtures that direct light downward. Fixtures with diffusers will help prevent glare. Evenly illuminating a wall with downlights called “wall washers” is another way to provide soft ambient light and also makes a room feel larger. Many surface-mounted and hanging luminaires project light in more than one direction, providing both uplighting and direct lighting in a single fixture.
Task lighting is bright light directed to a specific surface, like a countertop or desk, to illuminate activities such as reading, homework, meal preparation, or laundry. For reading and desk work, task lighting should be bright and well diffused and come from the side or from over the shoulders.
Overhead light often casts shadows from a person’s head and body onto the work surface. Also, light from directly overhead or in front of a person is prone to cause glare (veiling reflection) on shiny work surfaces, such as a glossy magazine. Light coming from one or both sides of the work reduces glare. For example, a table or floor lamp on the side is effective for reading or desk work. Under cabinet lighting can also be effective for desk work if placed toward the front of the cabinet on either side of the occupant (see Figure 5-22).
Where a computer screen is used, avoid bright sources of overhead light that reflect off the screen. Also keep the screen at right angles to windows if possible to avoid glare. For kitchen work, laundry, or hobbies, concentrated light from above can be effective as long as the fixtures are placed so the occupants do not shade the work surface. Under cabinet lighting is another effective strategy for placing bright task lighting on a kitchen counter or workbench.
Accent lighting, sometimes called “object lighting,” directs light to specific objects, such as artwork, furniture, plants, or architectural features. When lighting a single object or work of art, use a directional source, such as a PAR (parabolic aluminized reflector) or BR (bulged reflector) lamp in a track, or an adjustable recessed fixture, such as an “eyeball.” Position the fixture so the light strikes the wall at a 30-degree angle from the vertical.
When lighting a large picture or grouping of pictures, it is often best to illuminate the entire wall section with a wash of light from multiple track lights or adjustable recessed fixtures. For consistent lighting across the wall without a “scalloping” pattern, use special “wall washer” fixtures or non directional lamps (A-bulbs or compact fluorescent's) to diffuse the light beams (Figure 5-23).
Decorative lighting includes candlestick chandeliers and sconces, decorative table lamps, and other fixtures whose main function is to provide luminous “sparkle” to a room.
Many factors affect the illumination needed for a specific task. An often overlooked factor is the age of the occupants. At 60 years old, we need two to three times the light we needed at age 20, and also more shielding and diffusers since older eyes are more sensitive to glare. The other main factors in determining lighting requirements are how detailed the work is and the level of contrast and reflectance of the work surface.
Table 5-21 shows the recommended lighting along with common strategies for each type of room. For task lighting, the low numbers in each range represent the light needed for simple tasks with high contrast (reading large black type on white paper). The high number is for tasks with more detail or lower contrast (reading the newspaper). For very detailed, low-contrast work or for older persons, light levels of 100 footcandles are often needed.
The illumination level on a surface depends on many factors, including the colors of the room and furnishings and the type of lamp and fixture. High ceilings, dark colors, and diffusers on fixtures all reduce light levels. The commonly used black baffles in recessed lights reduce output by up to 40%. Tightly focused spots produce much higher light levels than wide floods. The distance from the light source is also critical. Doubling the distance to a lamp reduces the lighting level by a factor of four. So moving the light closer to the task is often the simplest way to provide a big boost in lighting levels.
As a starting point for design in kitchens, baths, home offices, and other brightly lit spaces, provide at least 2 watts of incandescent light or 3 4 watt of fluorescent light per square foot of floor area. In larger spaces, using multiple fixtures will provide more even lighting and reduce glare. Also, since lighting needs change throughout the day with changes in daylight and usage, it is good to provide flexibility by separately switching groups of lights and adding dimmers. Increase these minimums by 50 to 100% for:
There is a vast array of choices in light bulbs, known in the lighting industry as “lamps.” For residential lighting, the main choices are incandescent, halogen, low-voltage, tubular fluorescent, and compact fluorescent. Which lamp to choose for a given application will depend upon the amount of light needed (lumens), color of light desired, type of fixture (luminaire), and whether the application calls for a directed beam or a diffused light source.
Also, some lamps are more energy-efficient, providing more lumens for the same amount of electricity consumed. Fluorescent's are the most efficient, using up to 70% less energy than an equivalent incandescent bulb (see Table 5-22).
Incandescent light bulbs include the familiar non directional “A” lamps, as well as a variety of directional flood and spot lamps designated by an “R” or “BR.” Incandescent's. have a low color temperature of around 2700 K, which produces a warm light with lots of red and yellow tones that make skin, natural wood, and other warm colors look good. To some extent, things look good to us under incandescent light because it is what we are most accustomed to. Incandescent lamps are inexpensive and are easy to dim, but they are also the least efficient type of bulb and the shortest lived.
Halogen bulbs, also known as tungsten-halogen, is actually a kind of incandescent with more blue and less red light (3000 K), giving it a whiter appearance than standard incandescent lamps. Halogen lamps provide good color rendition and good light for reading and fine detail work. When dimmed, however, halogen light becomes more yellow, like standard incandescent lighting. Also, dimming can cause a halogen lamp to darken due to tungsten evaporation. Turning the lamp to full illumination for about 10 minutes will restore its full power.
Halogen lamps tend to be smaller, produce 10 to 15% more lumens per watt than standard incandescent's., and last about twice as long. They come in a wide range of beam spreads and wattages. However, since halogen lights burn very hot, they must be shielded from contact with other materials or they can create a fire hazard.
Also, the bulbs should not be touched without wearing a glove (since the oil from your skin can create a weak spot on the bulb), and should be cleaned with alcohol. Halogen PAR (parabolic aluminized reflector) lamps are enclosed in a protective glass casing, which allows them to be handled like ordinary bulbs. Low-Voltage lamps are tungsten-halogen, incandescent, or the newer xenon lamps, operating at 12 volts DC.
Their small size makes them ideal for under cabinet lighting, and their very precise beam control makes them well-suited to accent lighting of artwork. Many low-voltage fixtures allow the lamps to rotate within the housing to precisely aim the beam.
Low voltage lights use a step-down transformer to convert 120V line voltage to 12 volts DC. Most newer fixtures use solid-state electronics, which are more energy efficient and longer lasting than the older magnetic type. Transformers are either attached to the fixtures or installed remotely. Since the transformers, as well as the lamps and dimmers, emit a slight hum, remote location can be an advantage. However, locating the transformer too far from the fixtures can result in a loss of power and dimming of the lamps. When using dimmers with low-voltage lighting, make sure they are specifically designed for low voltage systems and for the specific type of transformer.
Fluorescent bulbs or lamps produce light by energizing the phosphor coating on the inside of a glass envelope. A device called the ballast regulates the power needed to start the lamp and keep it going. Older magnetic ballasts caused humming and flickering, but new electronic or solid-state ballasts have eliminated these problems.
Fluorescent's produce three to five times the output as incandescent lamps [per watt of energy used], last about ten times as long, and stay very cool. Because they reduce lighting bills by as much as 75%, and reduce cooling loads as well, they are heavily promoted by model energy codes and mandated in some areas. For example, the California Energy Code requires that the main lighting in kitchens and baths be fluorescent.
The downside of fluorescent's has always been their poor color rendering. Standard fluorescent's emphasize the blue range of the spectrum, giving skin an unflattering, pale appearance. Manufacturers have worked hard over the years to improve the light quality. So-called “deluxe” fluorescent's offer CRI (color rendering index) values in the 85 to 90 range but with a 25% loss of efficiency. To achieve CRIs in the high 90s without sacrificing energy efficiency, manufacturers use more expensive rare earth phosphors, creating triphosphor and quad-phosphor lamps.
Fluorescent lamps with high CRIs, and color temperatures within the range of 2700 to 3500K, create pleasing light for skin tones and natural wood and can blend in with incandescent lighting. In applications where color accuracy is important, such as laundry areas, lighting artwork, and certain hobbies, full-spectrum daylight lamps may be preferred. These lamps, which produce light similar to natural daylight, include General Electric’s Chroma 50 and Chroma 75.
Dimming also used to be a challenge with fluorescent's However, using solid-state dimming ballasts and special dimmers designed for fluorescent's can eliminate any humming sounds. These also allow a single dimmer switch to dim groups of fixtures with different length tubes.
Compact fluorescent lights have created a lot more flexibility, allowing fluorescent's to be used in recessed downlights, wall sconces, pendants, and just about any type of luminaire. Early compact fluorescent's were noisy, slow to start, and had a limited selection of color temperatures. Newer products, however, are quiet and typically have rapid-start ballasts. Dimmable ballasts are also available for compact fluorescent's, but are costly. As with tube fluorescent's, look for high CRIs and lower (warmer) color temperatures from 2700 to 3500K to blend in with incandescent and halogen lighting. All compact fluorescent's have a minimum 80 CRI.
While some compact fluorescent's have been introduced that mimic R and PAR-type reflector bulbs, directional lighting is best achieved with incandescent or halogen lamps. Fluorescent's are better used for ambient lighting, indirect lighting, and lighting of closets and storage areas. Although they cost $5 to $20 per bulb, depending on the wattage and configuration, they generally pay for themselves within two to three years in both energy savings and longevity of the bulbs.
There are literally thousands of lamps to choose from, but the most common in residential lighting are standard incandescent A lamps, 120-volt BR and PAR directional lamps, and low-voltage PAR and MR lamps, along with a variety of tubular and compact fluorescent's While different lamp manufacturers use different codes and abbreviations to label their lamps, most list the wattage first, followed by the bulb shape, width of the bulb (in eighths of an inch), and additional information about the shape and beam angle. For example, a 50PAR36/H/NSP8° is a 50-watt PAR lamp, 3 8 6 (4 1 2) inches across, halogen with an 8-degree narrow spot beam. Common abbreviations include the following:
Color temperature and color rendering index (CRI) are two different ways to characterize how colors appear under a light source. Color Temperature is expressed in degrees Kelvin, and for incandescent lights equals the temperature of the metal filament. For fluorescent's and other bulbs without filaments, it is the theoretical equivalent temperature.
Lower color temperatures indicate “warmer” light with more yellow and red tones, which complement skin and natural wood finishes. Higher color temperatures indicate “cooler” light with more blue and green tones, which renders faces harshly and tends to make skin look pale (Table 5-23).
Skin tones look best under lamps rated from 2700K (standard A-bulb) to 3500K and with a CRI over 80. Residential lamps range as high as 7500K for continuous spectrum fluorescents, such as GE’s Chroma 50 or 75. These simulate daylight and are good for detailed work where color accuracy is critical, but they give skin an unflattering greenish tone.
CRI is a rating on a scale of 1 to 100 of how accurately a lamp shows colored objects. The higher the CRI, the closer the colors look to a standard reference. For incandescent lamps and all others with a color temperature of 5000K or less, the reference is an incandescent or halogen bulb, which are both assigned CRIs of 100. For lamps with a color temperature of over 5000K, the reference is natural daylight, which also has a CRI of 100.
CRI numbers are best used to compare lamps with color temperatures within about 300K of each other. Colors will look very different under a 3000K lamp and a 6000K lamp with the same CRI.
While there are thousands of different luminaires on the market, they all fall into a few basic categories. Many mix more than one lighting strategy within a single fixture. All luminaires can be categorized as either direct lights, downlights, accent lights, or indirect lights. Many luminaires combine two or more of these strategies. For example, many dining room chandeliers include a downlight that provides accent or task lighting to the table top in addition to the fixture’s ambient lighting. Common fixture types and placement are covered below.
These include most surface-mounted fixtures on walls and ceilings, often with a diffusing globe or lens to reduce glare. In general, these are very efficient sources of light, but may also produce a lot of glare. Common types include surface-mounted ceiling fixtures, pendants, chandeliers, and sconces.
These are predominantly recessed ceiling lights that create a dramatic effect by casting pools of bright light on floors and work surfaces while leaving the ceiling in shadow. Used with A lamps, floods, or compact fluorescents, and spaced properly, downlights can create even general lighting. With more focused spot bulbs and special trims, they can function as task lighting, accent lighting, or wall washers.
When lighting a picture or single object, use a directional spot lamp in a shielded fixture. These are often track-mounted or adjustable recessed fixtures, such as “eyeballs.” To create even lighting over a large picture or group of pictures, it is best to use special “wallwasher” fixtures, or nondirectional lamps such as A-bulbs or compact fluorescents (Figure 5-23).
Bouncing light off light-colored walls and ceilings creates a soft and diffused illumination with little glare and gives a room a feeling of spaciousness. Examples include upward directed floor lamps and wall sconces, as well as site-built coves and valences, which can make use of cost-effective fluorescent tubes.
Coves reflect light off the upper walls and ceiling and dramatize a high or cathedral ceiling. Brackets provide downlighting as well to emphasize wall surfaces or artwork. Typical cove and bracket details are shown in Figure 5-26 (above) and Figure 5-27 (below). The shield should be designed to protect the bulbs from view within the room.
Recessed lighting can provide either ambient, task, or accent lighting, depending on the lamp type, its beam spread, and the type of reflector and trim used. Where recessed fixtures are used for ambient lighting, they should be spaced to provide even lighting without dark spots.
Track lighting follows the same design principles as recessed, but is best used for accent or task lighting in certain situations. It is particularly well-suited to situations where flexibility is required since fixtures may be easily moved as lighting needs change.
Beam spreads for directional lights vary depending on the lamp and fixture. For general lighting, choose a wide flood with a beam spread of at least 50 degrees. BR lamps are the most economical directional lamp and provide good enough beam control for general lighting. Standard A lamps with Alzak trim or compact fluorescents also provide good general lighting.
Halogen PAR lamps offer more precise beam control suitable for task or accent lighting. Low-voltage M-16 and PAR36 lamps offer very precise beam control, making them well-suited to accent lighting. Because of their narrow focus, spots produce higher illumination levels than floods but over a smaller area. Beam spreads and lighting levels for common directional lamps are shown in Table 5-24.
Typical residential recessed lights come in 4- to 7-inch diameters and can take a variety of different trims that significantly affect light output and glare.
For general lighting, a 5- to 7-inch diameter housing is commonly used. For accent lights, smaller 4-inch housings are available for both line-voltage and low-voltage figures. Special recessed housings are also available for compact fluorescents, sloped ceilings, and retrofit installations.
Standard recessed housings must be left uninsulated above. For insulated ceilings, use a can rated IC for “insulation contact.” Also make sure the housing is rated “airtight,” which is not true of all IC units. Air leaks through recessed lights can be a significant source of heat loss and moisture problems in cathedral ceilings.
The common black or white step baffles are designed for use with a PAR or BR lamp, although homeowners often put in the less expensive A19 bulbs.
Baffles reduce glare, but also cut light output by 50% or more for A lamps and up to 40% for directional lamps. Black baffles cut light output significantly more than white (Figure 5-28).
For maximum light output from a recessed lighting fixture, use a clear or gold specular reflector, also known as Alzak trim.
To reduce glare, which can be a problem with these highly efficient reflectors, it is best to use a deep-profile Alzak trim, offered by most recessed lighting manufacturers.
These work well with standard A19 bulbs as well as BR lamps (Figure 5-29). Gold Alzak is about 10% less efficient than the clear style.
For accent lighting, eyeballs and similar adjustable trims allow the homeowner to direct the light to the artwork or architectural feature being lit (Figure 5-30).
These are typically used with a narrow spot to provide bright focused light on a small area. Slotted wall wash trim is used to splash diffused light on broad areas of wall or bookcases. Nondirectional A lamps or compact fluorescents work well in this application. General recommendations for recessed lighting bulb wattage or bulb type and fixtrure spacing are given in Table 5-25.
The general rule for ambient or task lighting is to space recessed ceiling fixtures approximately the same distance apart as the beam spread at the work height, typically assumed to be 30 inches above the floor (36 inches for kitchen counters). The beam spread is the central cone of light, where the beam is at least 50% of the brightness at the center of the beam.
Most manufacturers publish beam spread data for their recessed lights with different trim options. Beam spreads and lighting levels for some common fixtures and lamps are shown in Table 5-26.
For ambient lighting, choose a compact fluorescent, A lamp, or wide flood with a beam angle of at least 50 degrees. Typical spacing for ambient lighting with recessed lights is 6 to 7 1/2 feet for an 8-foot ceiling, or 7 to 8 1/2 feet for a 9-foot ceiling. Spacing from the first row of lights to the wall is half this distance.
For accent lighting, space recessed or track fixtures so their light hits the wall at about 30 degrees. For lighting a large wall area, the distance between fixtures should be equal to or less than their distance from the wall (see Figure 5-23).
Due to risk of fire, the International Building Code and the National Electrical Code require that all fixtures installed in closets must be either surface-mounted or recessed and must completely enclose the bulb. Only incandescent or fluorescent lamps are allowed.
In addition, the fixture must be installed either in the wall above the door or on the ceiling and have the following clearances:
Kitchens require general ambient lighting as well as task lighting on sinks, ranges, counters, and eating areas. Given the high lighting needs of a kitchen, the energy savings from fluorescent lights can be substantial. Look for fluorescent bulbs with a CRI over 80 and a color temperature near 2800K to match standard incandescent lights, or 3500K to match halogen lights.
For efficient general lighting, use one or more enclosed ceiling fixtures with a white diffuser that illuminates the ceiling as well as the space below. In a very small kitchen, placing the ceiling fixture near the sink and counter can provide effective task lighting as well. For a softer glow in a kitchen, indirect lighting can also work nicely with lights placed in coves and above the cabinets to illuminate the ceiling.
Although not the most energy-efficient, recessed lighting has become a popular choice for kitchen lighting because of its sleek appearance and dramatic effect. For even lighting, use fixtures and lamps with wide beam spreads and spacing based on a 36-inch work plane (Figure 5-23). Also see the discussion on “Spacing,” page 202.
As a rough guide, the American Lighting Association suggests the following minimum lighting levels:
These numbers should be increased by 50 to 100% for indirect lighting, dark surfaces, lighting placed high in cathedral ceilings, or use of recessed lights with diffusers, baffles, or other light blocking trim.
Work counters, sinks, and cooktops all need high lighting levels. Where wall cabinets are present, under cabinet lighting provides excellent illumination for counters. Place lights as close as possible to the front of the cabinets to avoid glare reflecting off the work surface (Figure 5-23 shown above). Low-voltage xenon “festoon” lamps provide bright, even light similar to halogen but without the high temperatures and pressures, eliminating the safety concerns associated with halogen. Also, xenon lamps can be touched with bare skin and provide 10,000 hours of service.
An alternative for lighting at counters is to place a row of recessed fixtures directly over the outer edge of the counter. If used for task lighting, place fixtures about 36 inches apart for 8-foot ceilings or 48 inches apart for 10-foot ceilings (see Task Lighting in Table 5-25).
Sinks, cooktops, islands, and counters without cabinets above can be lit by small recessed downlights or track lighting. Mini-pendants with 12-volt halogen bulbs offer an attractive and functional way to illuminate islands, peninsulas, and eating counters (Figure 5-23).
Choose a pendant at least 12 inches less in diameter than the table’s smallest dimension and mount the fixture 27 to 36 inches above the table.
A 120-watt incandescent or 40- to 50-watt fluorescent fixture will generally provide sufficient illumination (see Figure 5-24).
Good lighting is critical at the bathroom mirror for shaving, makeup, and other tasks of personal hygiene. For optimal lighting, place strip lights or globe type light bars at least 16 inches long on each side of the mirror centered at 61 to 64 inches (about the average eye height). Wall sconces on either side are also an option for smaller mirrors. These provide even cross lighting without shadows or glare (see Figure 5-23).
For small mirrors under 30 inches wide, use about 75 watts of incandescent lighting or 20 watts of warm-white fluorescent on each side. For larger mirrors, use up to 150 watts of incandescent or 40 watts of fluorescent on each side. Additional lights across the top of larger mirrors are also helpful. If using fluorescents, select lamps with high CRIs and warm color temperatures in the 2700K to 3000K range.
Lighting from above the mirror only using globe-type light bars, a pair of recessed downlights, or a lighting soffit is acceptable as long as the vanity top is a light color. Otherwise, areas under the eyes, nose, and chin will be in shadow. If recessed fixtures are used, choose an A lamp, flood, or compact fluorescent for a diffused beam.
General Lighting. As a rule of thumb, provide one watt of incandescent or 1/3 to 1/2 watt of fluorescent light per square foot of floor space. Increase this by 50 to 100% for recessed lights, indirect lighting, or a room with dark surfaces. In a small bathroom, the mirror lights can also provide the ambient light. For larger baths, a separate ceiling fixture mounted near the tub and toilet can be useful for ambient light and reading. Finally, in a room with a high ceiling, indirect lighting with coves or uplights can create a feeling of spaciousness in a bathroom, along with a pleasing, soft glow.
A recessed light with a white diffuser mounted over the tub or shower will be appreciated by bathers. Electrical codes require that these fixtures be totally enclosed and rated for use in a damp location (tub area) or wet location (shower). Most require GFCI protection for their UL rating. In addition, fixtures must be at least 6 feet above the water line and switches must be a minimum of 5 feet from the edge of the bathtub or shower. Check with local codes for specific requirements.
-- Adapted with permission from Best Practices Guide to Residential Construction.
-- Adapted with permission from Best Practices Guide to Residential Construction.
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