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 Mobile ViewSTRUCTURAL INSPECTIONS & DEFECTS ADVANCED INSPECTION METHODS AGE of a BUILDING - how to determine FOUNDATION MATERIALS, Age, Types FRAMING MATERIALS, Age, Types FRAMING METHODS, Age, Types FRAMING SIZE & Spacing, Age, Types FRAMING TABLES, SPANS for DECKS Heating Equipment, Age, Types Historic Homes, Home Improvement Costs, Research Insulation Materials, Age, Types Nails and Hardware, Age, Types PLASTER & BEAVERBOARD & DRYWALL PLASTER TYPE IDENTIFICATION Plumbing Materials & Fixtures, Age, Types ROOFING MATERIALS, Age, Types Saw Cuts, Tool Marks, Age of Sears Kit Houses SIDING MATERIALS, Age, Types WINDOWS & DOORS, Age, Types ARCHITECTURE & BUILDING COMPONENT ID BARK SIDE DOWN on DECKS, TRIM, STEPS BASEMENT WATERPROOFING BEST CONSTRUCTION PRACTICES GUIDE BRICK FOUNDATIONS & WALLS BRICK STRUCTURAL WALL Loose Bulged Brick Thermal Expansion Cracking BRICK VENEER WALL Loose, Bulged BRICK WALL DRAINAGE WEEP HOLES BUCKLED FOUNDATIONS due to INSULATION? BUILDING SAFETY HAZARDS GUIDE BUILDING SETTLEMENT CHIMNEY CHASE Construction & Defects CHIMNEY INSPECTION DIAGNOSIS REPAIR COLUMNS & POSTS, DEFECTS CONCRETE FOUNDATIONS CONCRETE FOUNDATIONS, PRE-CAST Cracks, Checking or Splitting Beams & Log Homes CRAWL SPACES DECK & PORCH CONSTRUCTION DECK COLLAPSE Case Study DECK FINISHES COATINGS PRESERVATIVES DECK FLASHING LEAKS, ROT Case Study DECKS, ROOFTOP CONSTRUCTION DEBRIS STAINING on ROOFS DEFINITIONS of Mobile Home, Doublewide, Modular, Panelized DEFINITIONS of ENGINEERED WOOD OSB LVL etc MDO Plywood HDO Plywood I-JOISTS, Wood Roof Floor LVL Laminated Veneer Lumber, Beams OSB - Oriented Strand Board PLYWOOD Roof, Wall, Floor Decks & Sheathing PSL Lumber DEW POINT CALCULATION for WALLS DEW POINT TABLE - CONDENSATION POINT GUIDE DISASTER BUILDING INSPECTION & REPAIR SAFEY EARTHQUAKE DAMAGED FOUNDATIONS ENERGY SAVINGS in BUILDINGS ENGINEERED WOOD Flooring ENGINEERED WOOD Products FLOOD DAMAGE ASSESSMENT, SAFETY & CLEANUP FLOODS IN BUILDINGS-mold FLOOR, ENGINEERED WOOD & LAMINATES FLOOR FRAMING & SUBFLOOR for TILE FLOOR TYPES & DEFECTS FLOOR TILE ASBESTOS IDENTIFICATION FLOOR TILE HISTORY & INGREDIENTS FOOTING & FOUNDATION DRAINS FOOTINGS EXPOSED, Repair Methods FOUNDATION BULGE or LEAN MEASUREMENTS FOUNDATION CONSTRUCTION TYPES FOUNDATION CONTRACTORS, ENGINEERS FOUNDATION CRACKS & DAMAGE GUIDE FOUNDATION FAILURES by TYPE & MATERIAL FOUNDATION FAILURES by MOVEMENT TYPE FOUNDATION INSPECTION METHODS FOUNDATION INSULATION OPTIONS FOUNDATION MATERIALS, Age, Types FOUNDATION REPAIR METHODS FOUNDATION WATERPROOFING FRAMING DAMAGE, INSPECTION, REPAIR FRAMING DETAILS for BETTER INSULATION FRAMING DETAILS for DOUBLE WALL HOUSES FRAMING CONNECTORS & JOIST HANGERS FRAMING FASTENERS, NAILS, SCREWS, & HIDDEN FRAMING & SUBFLOOR for TILE FRAMING MATERIALS, Age, Types Dimensional Lumber ENGINEERED WOOD Products Hewn beams & planks Log construction SHEATHING, FIBERBOARD Sheathing, Gypsum board Sheathing Homasote & Other Board SHEATHING, OSB SHEATHING, Plywood SHEATHING, FOIL FACED - VENTS STRAW BALE CONSTRUCTION TRUSSES, Floor & Roof FRAMING METAL STUD PERFORMANCE FRAMING METHODS, Age, Types FRAMING SIZE & Spacing, Age, Types FRAMING TABLES, SPANS for DECKS FRENCH DRAINS FROST HEAVES, FOUNDATION, SLAB FRT PLYWOOD GALVANIC SCALE & METAL CORROSION GLUES ADHESIVES, EXTERIOR CONSTRUCTION GRADING & SITE WORK, EXTERIOR GUTTERS & DOWNSPOUTS HOUSE PARTS, DEFINITIONS HOUSEWRAP INSTALLATION DETAILS I-JOISTS, Wood Roof Floor KIT HOMES, Aladdin, Sears, Wards, Others ALADDIN KIT HOUSES SEARS KIT HOUSES LEED GREEN BUILDING CERTIFICATION LOG HOME GUIDE LVL Laminated Veneer Lumber, Beams MOBILE HOMES, DOUBLEWIDES, TRAILERS MODULAR HOME CONSTRUCTION MOISTURE CONTROL in BUILDINGS NOISE / SOUND DIAGNOSIS & CURE OSB - Oriented Strand Board PANELIZED CONSTRUCTION PLASTER BULGES & PILLOWS PLASTER, LOOSE FALL HAZARDS PLYWOOD Roof, Wall, Floor Decks & Sheathing PORCH CONSTRUCTION & SCREENING PRE-CUT & KIT HOMES Preservative-Treated Framing Lumber RAILINGS, DECK & PORCH RAILINGS, STAIRWAY RETAINING WALL DESIGNS, TYPES, DAMAGE RETAINING WALL GUARD RAILINGS ROT, FUNGUS, TERMITES ROT, TIMBER FRAME SEARS KIT HOUSES SEPTIC & CESSPOOL SAFETY SHEATHING, FIBERBOARD SHEATHING, Gypsum board SHEATHING Homasote & Other Board SHEATHING, OSB SHEATHING, Plywood SHEATHING, FOIL FACED - VENTS SIDING, Sheathing Identification - Photo Guide SINKHOLES, WARNING SIGNS SINKING BUILDINGS SLAB CRACK EVALUATION SLAB CRACK REPAIR Splits in Structural Wood Beams STAIN & BIODETERIORATION AGENT CATALOG STAINS on BUILDINGS - QUICK GUIDE STAIN DIAGNOSIS on BUILDING EXTERIORS STAIRS, RAILINGS, LANDINGS, RAMPS STONE CLEANING METHODS STONE FOUNDATIONS STONE VENEER WALLS STRAW BALE CONSTRUCTION STRESS SKIN INSULATED PANELS STUCCO WAll FAILURES DUE TO WEATHER STUCCO WALL METHODS & INSTALLATION STUCCO OVER FOAM INSULATION STUCCO PAINT FAILURES SUMP PUMPS GUIDE SWEATING (CONDENSATION) on PIPES, TANKS TERMITES, ROT THERMAL EXPANSION of MATERIALS THERMAL MASS in BUILDINGS TRIM, EXTERIOR CHOICES, INSTALLATION TRUSS UPLIFT, ROOF TRUSSES, Floor & Roof VAPOR BARRIERS & CONDENSATION in BUILDINGS VENTILATION in buildings VINYL Siding or PLASTIC Window ODORS in buildings VINYL CHLORIDE HEALTH INFO WATER BARRIERS, EXTERIOR BUILDING WATER ENTRY in BUILDINGS WIND ENERGY SYSTEMS WIND TURBINES & LIGHTNING WIND WASHING INSULATION At EAVES WINDOWS & DOORS, Age, Types WINTERIZE A BUILDING WOOD FOUNDATIONS More Information |
This article series defines and illustrates basic types of engineered lumber and wood products such as plywood and OSB sheathing, Laminated Veneer Lumber LVL used for beams and headers, High Density Overlay HDO and Medium Density Overlay MDO plywood, and Parallel Strand or PSL lumber. We also define and illustrate wood I-Joists used in floor and roof construction. InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers nor with topics or services discussed at this website.This article series describes wood products used in construction including engineered lumber, OSB, and Plywood products. Our page top photo shows single and built-up LVL beams along with a conventional 2x4 and a built-up 2x6 beam (at left in the photo) at a wood frame construction project in New York. © Copyright 2012 InspectAPedia.com, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use page top links to major topics or use links at the left of each page to navigate within topics and documents at this website. Green links show where you are in a document series or at this website. Definitions of HDO Plywood, MDO Plywood, Glulam, LVL, Microlam, PSL, and OSB Trim and Lumber: Structural Composite LumberDefinition & Characteristics of "LVL" - Laminated Veneer Lumber, Beams, HeadersLaminated veneer lumber is an "engineered wood product", developed in the 1960's, is produced by gluing together layers of wood veneers with the wood grains in parallel. Illustraged in our photographs of LVL beams in use at a Poughkeepsie NY Project, our example LVL beams are made of fifteen laminated wood plies. Multiple laminated veneer lumber beams can be assembled to provide greater strength to carry greater loads. In our LVL beam photo (below left) you will see that a higher-capacity LVL beam may be constructed as a built-up beam using multiple individual members nailed or nailed and glued together. Our LVL composition closeup photo (below right) shows how the ends of individual plies within a single LVL beam may overlap within the product. [Click any image to see an enlarged, detailed view].
Because individual wood ingredient defects in a laminated wood product will not extend beyond a single layer or "veneer" of wood, the overall laminated product is stronger than a piece of lumber of the same dimensions sawn from an individual tree. This approach also permits construction of large structural beams from smaller-diameter and lower-lumber-grades of trees. As we illustrate in our LVL beam photographs (above) and as we also discuss at TRIM, EXTERIOR CHOICES, INSTALLATION:
Like LVL beams, LVL trim is dimensionally stable and is easy to cut, nail, and install, similar to a piece of plywood. Its weight falls in between solid wood and hardboard. It can be used for fascia, casings, corner boards, and most other exterior trim, and is available in lengths from 8 to 24 feet. According to Laminated Veneer Lumber, Overview [Quoting:]
The example photograph of LVL boards used to form board-and-batten trim on a building exterior is from the above document.
Laminated beams such as GluLam™ (photo at above left) or microlam structural wood beams (see LVL or laminated veneer lumber earlier in this article and illustrated further below). Layers of wood are glued (laminated) together with heat, resin binder, and pressure to form a very strong structural member that can be produced in regular sizes and lengths. Unlike plywood or OSB, LVL lumber uses wood fragments that are all oriented in the same direction to produce very stiff beams that generally have greater span capacity than sawn lumber. GluLam produces laminated wood beams, timbers, I-joists, and other engineered wood products.
See TRIM, EXTERIOR CHOICES, INSTALLATION for a discussion of use of LVL for exterior trim. See Laminated Veneer Lumber, Overview of the Product for a nice collection of examples of use of LVL products and a brief history of this material. Definition & Characteristics of PlywoodDetails about plywood products used in building construction for roof or wall decking or sheathing and for subfloors are at PLYWOOD Roof, Wall, Floor Decks & Sheathing. Excerpts are below.
Our photo (left) shows 1/2-inch CDX plywood installed as exterior wall sheathing on a home being constructed in Minneapolis, Minnesota. Plywood sheets are named according to the sheet thickness, the quality of its exterior or exposed veneers (A = clear, no knots, C/D - construction grade, etc), and its thickness. Plywood products are also selected for interior or exterior use based on the weather resistance of the glues used to glue the veneers together (exterior plywood uses exterior glues), and finally on the condition of interior veneers or plies of wood. Plywood used for floor sheathing or underlayment beneath carpeting, for example, is selected without interior voids so that someone's shoe-heel won't puncture through a clear top veneer of wood into a hidden void below. As we discuss also at FRAMING MATERIALS, Age, Types and at SHEATHING, Plywood: PLYWOOD Roof, Wall, Floor Decks & Sheathing (1905 - present as a construction material in North America) is sheet material made of thin veneers of wood that are laid with wood grains in alternating direction, glued, heated, and pressed together. Interior plywood is generally glued with urea formaldehyde based glues; exterior plywood and marine plywood use phenolic formaldehyde glues and are water resistant. Our photo (left) shows both fire-retardant plywood roof sheathing (left half of the photo and center top and bottom) and OSB roof sheathing (center of photo and right edges of photo). While modern plywood products use a variety of glues, heat, and pressure to produce the product, plywood has been around at least since 3500 BC when a glued-veneer version was produced in Egypt. The furniture industry has had a long history of gluing thin fine-wood veneers to a cheaper wooden base - a process similar to the production of plywood itself. The invention of the rotary lathe (ca 1850) by Immanuel Nobel (1801 - 1872) is what made modern plywood possible by permitting manufacturers to cut large thin (but thicker than wood veneers) sheets of wood from logs. The wood sheets are placed at right angles to one another and glued together. The cross-grain construction combined with glue produces a strong, uniform material that is used for both enclosure and for structural stiffness in frame construction of building walls and roofs. The properties of plywood, including its tolerance to weather exposure (marine plywood) depend on the glues and finishes used. Both softwood and hardwoods are used in plywoods, and fine wood veneer finishes are also available (for furniture use). The first plywood made in the Western U.S. was produced by the Portland Manufacturing Company in Oregon in 1905, a company founded four years earlier by Gustav A. Carlson, F.S. Doernbecher, and M.L. Holbrook. Peter Autzen bought out Doernbecher and Holbrook. It was Autzen's son, Thomas, who made key progress solving problems with bonding the veneers together. Originally the Portland Manufacturing company had produced fruit baskets, crates, and drums, experience which we pose gave the owners familiarity with cutting thin strips of wood (baskets) that remained flexible for use in a manufacturing process. Their plywood was exhibited at the 1905 Worlds' Fair in Portland, Oregon. Interestingly, the first exhibition of plywood as a building product in the Northwest was in a log structure, the Forestry Building in Portland, OR where it was displayed until that building burned in 1964. In 1924 plywood sales were still primarily to door producers, but by 1928 the company had increased production and plywood was being used in automobile bodies. In that year the Pacific Coast Plywood Manufacturers, Inc. (PCPM)was formed jointly with Elliot Bay Mill Co. (Seattle), Walton Veneer Co. (Everett WA), and Washington Veneer Co. (Olympia WA). But PCPM was dissolved after the 1929 Stock Market crash. The appeal and success of plywood as a building material are based on quite a few factors including increased construction speed (consider nailing up 4x8 sheets of plywood versus individual tongue and groove exterior building sheathing or roofing), product uniformity and strength, and the reduction of waste compared with cutting sheathing boards out of logs. Also see FIRE RETARDANT PLYWOOD. Definition & Characteristics of PSL Lumber"PSL" or Parallel Strand Lumber is similar to LVL and is used in the same applications as LVL lumber and trim, but PSL lumber permits more defects in its veneers, creating a more random wood pattern on its visible surfaces. Definition & Characteristics of MDO Plywood"MDO" plywood (Medium Density Overlay) is constructed of a core of overlapping veneers of wood, but with a surface layer of medium density fiber. The resulting product has a smooth surface. MDO plywood can be used once as a concrete form material, but should not be re-used for that purpose. See TRIM, EXTERIOR CHOICES, INSTALLATION for a discussion of use of MDO plywood for use on building soffits. Definition & Characteristics of HDO Plywood"HDO" (High Density Overlay) plywood is similar to MDO Plywood described just above. HDO plywood also is constructed wit a core of overlapping wood veneers, but instead of using a medium density fiber for its external surfaces, HDO plywood uses a high-density fiber exterior. HDO plywood products, having a harder exterior surface, can be re-used several time for concrete forms. APA (The Engineered Wood Association) provides an HDO/MDO Plywood Product Guide that offers details about these products. Definition & Characteristics of OSB - Oriented Strand BoardDetails about OSB sheathing panels are at SHEATHING, OSB where we provide more details and photo examples of OSB Oriented Strand Board sheathing use. Excerpts are below. "OSB" or Oriented Strand Board wood products is similar to LVL and PSL, but OSB is produced in sheets (typically 4' x 8' in size) and is constructed of shorter strands of wood or even (in the case of 4' x 8' sheets) wood chips that may be roughly rectangular in shape. Developed in the 1980's, oriented strand board is an engineered wood product in which strands and flakes of wood are cut from straight, low-knot small-diameter logs, usually aspen or white birch. The wood strands and flakes of OSB are glued (or "bonded") together with a phenol-formaldehyde resin binder (forming a waterproof glue), heated (to at least 120 degF), and are compressed and flattened using pressure. Other chemical binders may be used in OSB products, and the OSB sheathing surface may have a wax coating to improve water resistance of the product. Our photographs of OSB "plywood" below illustrate that the wood fragments glued together under heat and pressure are deliberately oriented randomly to produce greater strength than would be achieved if these small individual fragments were all oriented in the same direction
Our second OSB sheathing photo (above right) shows fire retardant treated plywood roof sheathing (photo-left) and OSB roof decking (photo-right) sheathing the roof of a multi-unit condominium building. Properties of OSB PanelsIn an OSB panel the two exterior surface layers of wood strands are oriented parallel to the long axis of the panel. In the interior OSB panel layer or "core layer" strands are oriented either randomly or across the short axis of the OSB panel. In overall thickness the ratio of face panels to core panel ranges from 40:60 to 60:40. According to the Universite Laval and also Timberco, the dimensions of wood strands used in OSB are specified in industry standards; most producers of OSB use a combination of strands that are up to 6" long and 1" wide or from another source, 19-40 mm in width and 90 to 100mm in length. OSB is a modern wood product that developed from earlier 1970's "waferboard" product. In 1990 the Structural Board Association was formed. By 1996 there were 38 OSB producers in North America. But unlike waferboard whose composite wood chips were place randomly, an oriented strand board product is made from wood chips that are deliberately oriented with respect to one another to provide greater strength. As a result, modern OSB products are rated at the same strength as plywood products. OSB roofing panels are available with a perforated (breathable) foil radiant barrier affixed to the pane's interior surface. See SHEATHING, OSB for more details and photo examples of OSB Oriented Strand Board sheathing use. Wood I-Joists Used in Floor & Roof ConstructionOur photo (below left) illustrates wood I-joists used in construction of building floors and roofs. You will observe that the center web of the I-joist is consructed of OSB sheathing material that we illustrated just above. Our second photo (below right) shows common lumber markins found on the solid wood top and bottom chords of wood I-joists.
Engineered wood floor trusses (photos above and below) such as I-Joists originally were constructed using a plywood web beginning in 1977, and modified by by Trus-Joist in 1969 to use laminated veneer lumber (LVL) and OSB-like laminated wood fiber web (shown in photos above left and below in combination with a steel beam).
Wood and steel roof and floor trusses are discussed separately at TRUSSES, Floor & Roof and at at TRUSS UPLIFT, ROOF. Listing submissions are welcome from websites whose content, services, or products are appropriate for our readers. To provide your link exchange information and our link exchange policy see InspectAPedia.com - Directory Listing & Link Exchange Instructions There are no listing fees & no conflicts of interest. We reserve the right to list or not list individuals or companies and to provide notice of consumer compliments or complaints. The design and content found at InspectAPedia.com® are © Copyright protected, All Rights Reserved. Contents of this website may not be copied in any form. Our main website topics listed at page left and page top provide in-depth, un-biased, expert information on building defect inspection, diagnosis, & repair. Questions & Answers regarding this article. Ask a Question or Search InspectAPediaHTML Comment Box is loading comments...
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