FLOOR, WOOD MOISTURE - CONTENTS: Flooring, effects of moisture on floors. Moisture Content in Wood Affects Wood Floor Shrinkage, Swelling, Gaps, Finishes. Need for Acclimatization of Wood Flooring Before Installation
InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.
Moisture in wood & wood floors:
This article explains the effects of moisture on wood floors and reviews the proper moisture levels necessary when working with or installing a wood floor.
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.
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.
[Click to enlarge any image]
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. While there is wide variation among wood species and among individual boards, Simpson & TenWolde put the shrinkage percent from green to oven-dry moisture content in Coastal Douglas Fir at 1.8% radial, 7.6% tangential, and 12.4% volumetric. - (Simpson 1999 US FPL)
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.
Need for Acclimatization of Wood Flooring Before Installation
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
Our photo of an exploded wood floor in an old gymnasium (below a roof leak) demonstrates that the effects of excessive moisture on an installed wood floor can be extreme. Details are
at FLOOR WOOD, DAMAGE DIAGNOSIS. - DF.
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
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.
Try the search box below or CONTACT US by email if you cannot find the answer you need at InspectApedia.
Jan 30, 2014) Phil said:
What % of moisture or water penetration into Drywall can it reach before it can not be dried and has to be removed. Also, if there is a time limit on when you have to start the drying process.
Phil, that's an interesting question and I haven't thought about wet drywall quite that way. Let's try this:
If drywall is wet above 18% or so, even if just measured on the drywall surface, then conditions are ripe for mold formation; Generally the rate at which mold will grow on wet drywall depends on moisture levels and temperature; While there are molds that will grow under just about any condition, in buildings drywall mold of any of about 40 common genera/species will show up in 24-48 hours.
Wetter drywall grows different species (such as Stachybotrys chartarum) than less-wet but still too-wet drywall (18% say) (such as Aspergillus sp.).
So I would say that regardless of how wet the drywall is, if we could get it dry - say at 12% or less throughout its thickness - in 24-48 hours and if we don't already see mold growth on it, we're probably OK.
Search InspectApedia for
Mold on Walls, Drywall, or "Sheetrock®"
where I will re-post this question and where you will find more detail
Thanks for asking
Question: high utility bills with radiant heat floor
(Dec 12, 2014) Margo said:
I live in a small, single-level slab on grade duplex rental in Superior, WI built in early 2012 with water-based radiant heat as the only heat source and no cooling system. What could be causing the following:
1. Oozing of a substance that looks and feels like wet sand from between the seems of the flooring during warmer months
2. Worms coming from either the seams or the exterior edges of the home in warmer months
3. Warping and cupping at the seams of the flooring, including a couple of spots where a perfect circle can be seen in the flooring (about the size of a baseball)
4. Visible gaps at some seams of the flooring (about 1/8 inch each)
5. Utility bills are about twice as high as one would expect, going over $300/month in winter (around $80 in summer)
Margo it sounds to me as if water is leaking under your floor and that there are various infestations that need to be addressed as well, perhaps, as structural damage.
If the leak ins in a radiant heat floor that could explain abnormal heating bills.
Ask a Question or Search InspectApedia
Use the "Click to Show or Hide FAQs" link just above to see recently-posted questions, comments, replies, try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.
Steve Bliss's Building Advisor at buildingadvisor.com helps homeowners & contractors plan & complete successful building & remodeling projects: buying land, site work, building design, cost estimating, materials & components, & project management through complete construction. Email: email@example.com
Steven Bliss served as editorial director and co-publisher of The Journal of Light Construction for 16 years and previously as building technology editor for Progressive Builder and Solar Age magazines. He worked in the building trades as a carpenter and design/build contractor for more than ten years and holds a masters degree from the Harvard Graduate School of Education.
Excerpts from his recent book, Best Practices Guide to Residential Construction, Wiley (November 18, 2005) ISBN-10: 0471648361, ISBN-13: 978-0471648369, appear throughout this website, with permission and courtesy of Wiley & Sons. Best Practices Guide is available from the publisher, J. Wiley & Sons, and also at Amazon.com
Doggett, Steven M., "Unexpected Expansion of Fiber Cement Panels", [PDF] The Building Exnclosure (website), (14 Feb 2012), retrievedf 12/21/2014, original source: https://builtenv.wordpress.com/2012/02/14/ unexpected-expansion-of-fiber-cement-panels/
Simpson, William, TenWolde, Anton, "Physical Properties and Moisture Relations of Wood", [PDF] from U.S. FPL, Forest Products Laboratory, Wood Handbook - Wood as an engineering material", 1999, Gen. Tech. Rep. FPL-GTR-113, Madison WI, U.S. Department of Agriculture (USDA) Forest Service, FPL. - retrieved 12/20/2014, original source: http://www.woodweb.com/Resources/wood_eng_handbook/Ch03.pdf
Skaar, C., Wood Water RElations, 1988, Springer-Verlag, New York 1988
Stamm, A.J., Loughborough W.K., Thermodynamics of the swelling of wood, Journal of Physical Chemistry 1935, 39(1):121
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
"The Elimination of Unsafe Guardrails, a Progress Report," Elliott O. Stephenson, Building Standards, March-April 1993
"Are Functional Handrails Within Our Grasp" Jake Pauls, Building Standards, January-February 1991
Access Ramp building codes:
Access Ramp Standards:
ADA (Americans with Disabilities Act), Public Law 101-336. 7/26/90 is very often cited by other sources for good design of stairs and ramps etc. even where disabled individuals are not the design target.
ANSI A117.4 Accessible and Usable buildings and Facilities (earlier version was incorporated into the ADA)
ASTM F 1637, Standard Practice for Safe Walking Surfaces, (Similar to the above standards)
Asbestos products and their history and use in various building materials such as asphalt and vinyl flooring includes discussion which draws on ASBESTOS, ITS INDUSTRIAL APPLICATIONS, ROSATO 1959, D.V. Rosato, engineering consultant, Newton, MA, Reinhold Publishing, 1959 Library of Congress Catalog Card No.: 59-12535 (out of print).
Asbestos Identification and Testing References
Asbestos Identification, Walter C.McCrone, McCrone Research Institute, Chicago, IL.1987 ISBN 0-904962-11-3. Dr. McCrone literally "wrote the book" on asbestos identification procedures which formed
the basis for current work by asbestos identification laboratories.
Stanton, .F., et al., National Bureau of Standards Special Publication 506: 143-151
Pott, F., Staub-Reinhalf Luft 38, 486-490 (1978) cited by McCrone
ASHRAE resource on dew point and wall condensation - see the ASHRAE Fundamentals Handbook, available in many libraries. The following three ASHRAE Handbooks are also available at the InspectAPedia bookstore in the third page of our Insulate-Ventilate section:
2005 ASHRAE Handbook : Fundamentals: Inch-Pound Edition (2005 ASHRAE HANDBOOK : Fundamentals : I-P Edition) (Hardcover), Thomas H. Kuehn (Contributor), R. J. Couvillion (Contributor), John W. Coleman (Contributor), Narasipur Suryanarayana (Contributor), Zahid Ayub (Contributor), Robert Parsons (Author), ISBN-10: 1931862702 or ISBN-13: 978-1931862707
2004 ASHRAE Handbook : Heating, Ventilating, and Air-Conditioning: Systems and Equipment : Inch-Pound Edition (2004 ASHRAE Handbook : HVAC Systems and Equipment : I-P Edition) (Hardcover)
by American Society of Heating, ISBN-10: 1931862478 or ISBN-13: 978-1931862479
"2004 ASHRAE Handbook - HVAC Systems and Equipment The 2004 ASHRAE HandbookHVAC Systems and Equipment discusses various common systems and the equipment (components or assemblies) that comprise them, and describes features and differences. This information helps system designers and operators in selecting and using equipment. Major sections include Air-Conditioning and Heating Systems (chapters on system analysis and selection, air distribution, in-room terminal systems, centralized and decentralized systems, heat pumps, panel heating and cooling, cogeneration and engine-driven systems, heat recovery, steam and hydronic systems, district systems, small forced-air systems, infrared radiant heating, and water heating); Air-Handling Equipment (chapters on duct construction, air distribution, fans, coils, evaporative air-coolers, humidifiers, mechanical and desiccant dehumidification, air cleaners, industrial gas cleaning and air pollution control); Heating Equipment (chapters on automatic fuel-burning equipment, boilers, furnaces, in-space heaters, chimneys and flue vent systems, unit heaters, makeup air units, radiators, and solar equipment); General Components (chapters on compressors, condensers, cooling towers, liquid coolers, liquid-chilling systems, centrifugal pumps, motors and drives, pipes and fittings, valves, heat exchangers, and energy recovery equipment); and Unitary Equipment (chapters on air conditioners and heat pumps, room air conditioners and packaged terminal equipment, and a new chapter on mechanical dehumidifiers and heat pipes)."
1996 Ashrae Handbook Heating, Ventilating, and Air-Conditioning Systems and Equipment: Inch-Pound Edition (Hardcover), ISBN-10: 1883413346 or ISBN-13: 978-1883413347 ,
"The 1996 HVAC Systems and Equipment Handbook is the result of ASHRAE's continuing effort to update, expand and reorganize the Handbook Series. Over a third of the book has been revised and augmented with new chapters on hydronic heating and cooling systems design; fans; unit ventilator; unit heaters; and makeup air units. Extensive changes have been added to chapters on panel heating and cooling; cogeneration systems and engine and turbine drives; applied heat pump and heat recovery systems; humidifiers; desiccant dehumidification and pressure drying equipment, air-heating coils; chimney, gas vent, fireplace systems; cooling towers; centrifugal pumps; and air-to-air energy recovery. Separate I-P and SI editions."
Brick Nogging, Historical Investigation and Contemporary Repair, Construction Specifier, April 2006. Historical use of brick in timber-framed buildings, drawing on the investigations of the Kent Tavern in Calais, VT.
"Brick nogging is a European method of construction which was brought to the new world in the early-nineteenth century. It was a common construction method that employed masonry as infill between the vertical uprights of wood framing." -- quoting the web article review.
Building Research Council, BRC, nee Small Homes Council, SHC, School of Architecture, University of Illinois at Urbana-Champaign, brc.arch.uiuc.edu. "The Small Homes Council (our original name) was organized in 1944 during the war at the request of the President of the University of Illinois to consider the role of the university in meeting the demand for housing in the United States. Soldiers would be coming home after the war and would be needing good low-cost housing. ... In 1993, the Council became part of the School of Architecture, and since then has been known as the School of Architecture-Building Research Council. ... The Council's researchers answered many critical questions that would affect the quality of the nation's housing stock.
How could homes be designed and built more efficiently?
What kinds of construction and production techniques worked well and which did not?
How did people use different kinds of spaces in their homes?
What roles did community planning, zoning, and interior design play in how neighborhoods worked
Energy Savers: Whole House Systems Approach to Energy Efficient Home Design [copy on file as /interiors/Whole_House_Energy_Efficiency_DOE.pdf ] - U.S. Department of Energy
"Energy Savers: Whole-House Supply Ventilation Systems [copy on file as /interiors/Energy_Savers_Whole-House_Supply_Vent.pdf ] - ", U.S. Department of Energy energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11880?print
"Energy Savers: Whole-House Exhaust Ventilation Systems [copy on file as /interiors/Energy_Savers_Whole-House_Exhaust.pdf ] - ", U.S. Department of Energy energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11870
"Energy Savers: Ventilation [copy on file as /interiors/Energy_Savers_Ventilation.pdf ] - ", U.S. Department of Energy
"Energy Savers: Natural Ventilation [copy on file as /interiors/Energy_Savers_Natural_Ventilation.pdf ] - ", U.S. Department of Energy
"Energy Savers: Energy Recovery Ventilation Systems [copy on file as /interiors/Energy_Savers_Energy_Recovery_Venting.pdf ] - ", U.S. Department of Energy energysavers.gov/your_home/insulation_airsealing/index.cfm/mytopic=11900
"Energy Savers: Detecting Air Leaks [copy on file as /interiors/Energy_Savers_Detect_Air_Leaks.pdf ] - ", U.S. Department of Energy
"Energy Savers: Air Sealing [copy on file as /interiors/Energy_Savers_Air_Sealing_1.pdf ] - ", U.S. Department of Energy
Falls and Related Injuries: Slips, Trips, Missteps, and Their Consequences, Lawyers & Judges Publishing, (June 2002), ISBN-10: 0913875430 ISBN-13: 978-0913875438 "Falls in the home and public places are the second leading cause of unintentional injury deaths in the United States, but are overlooked in most literature. This book is unique in that it is entirely devoted to falls. Of use to primary care physicians, nurses, insurance adjusters, architects, writers of building codes, attorneys, or anyone who cares for the elderly, this book will tell you how, why, and when people will likely fall, what most likely will be injured, and how such injuries come about. "
Fiberglass: Indoor Air Quality Investigations: Health Concerns About Airborne Fiberglass: Fiberglass in Indoor Air from HVAC ducts, and Building Insulation
Gypsum Construction Guide, National Gypsum Corporation
Construction Handbook [purchase at Amazon.com] H17, Technical
Folder SA920 and PM2, PM3 and PM4, United States Gypsum Company, 125 South Franklin ST., PO Box 806278, Chicago, IL 60680-4124,
Humidity: What indoor humidity should we maintain in order to avoid a mold problem?
Ice Dam Leaks in building attics and roof cavities, how to inspect for evidence of leaks, identify causes, and correct bad attic ventilation, improper roof venting, and these causes of attic mold or roof structure damage
"Insulation: Adding Insulation to an Existing Home [copy on file as /interiors/Insulation_Adding_DOE.pdf ] - ," U.S. Department of Energy - tips on how to do your own check for the presence of absence of insulation in a home
Insulation: Selecting Insulation for New Home Construction [copy on file as /interiors/New_Home_Insulation_DOE.pdf ] - , U.S. Department of Energy -
"Your state and local building codes probably include minimum insulation requirements, but to build an energy-efficient home, you may need or want to exceed them. For maximum energy efficiency, you should also consider the interaction between the insulation and other building components. This is called the
"whole-house systems design approach" [copy on file as /interiors/Whole_House_Energy_Efficiency_DOE.pdf ] -
Insulation Types [copy on file as /interiors/Insulation_Types_DOE.pdf ] - , table of common building insulation properties from U.S. DOE. Readers should see INSULATION R-VALUES & PROPERTIES our own table of insulation properties that includes links to articles describing each insulation material in more detail.
Lath & Plaster Systems [copy on file as /interiors/LathPlaster_Nat_Gypsum.pdf ] - , 092300/NGC, National Gypsum Lath and Plaster Systems, National Gypsum Corporation, 800-628-4662 describing National Gypsum's Kal-Kore brand plaster base
Lighting, proper use of: proper aiming of a good flashlight can disclose hard to see but toxic light or white mold colonies on walls.
Metal Lath Specifications, Specification for metal lath and accessories, Lath and Plaster [copy on file as/interiors/Amico_lath-inside.pdf ] - from Amico, a lath and plaster accessory producer.
The National Institute of Standards and Technology, NIST (nee National Bureau of Standards NBS) is a US government agency - see www.nist.gov
"A Parametric Study of Wall Moisture Contents Using a Revised Variable Indoor Relative Humidity Version of the "Moist" Transient Heat and Moisture Transfer Model [copy on file as/interiors/MOIST_Model_NIST_b95074.pdf ] - ", George Tsongas, Doug Burch, Carolyn Roos, Malcom Cunningham; this paper describes software and the prediction of wall moisture contents. - PDF Document from NIS
Pergo AB, division of Perstorp AB, is a Swedish manufacturer or modern laminate flooring products. Information about the U.S. company can be found at http://www.pergo.com where we obtained historical data used in our discussion of the age of flooring materials in buildings.
Piquet Wall Construction: See this photo of
piquet wall construction - involving timber-framed wall construction with long top girts, diagonal timber bracing, and small diameter logs
placed vertically along with concrete chinking to fill in the wall plane.
Plank House Construction: weblog from plankhouse.wordpress.com/2009/01/25/plank-house-construction/ and where plank houses were built by native Americans, see
Large 1:6 Scale Plank House Construction / P8094228,
Photographer: Mike Meuser
06/12/2007 documented at yurokplankhouse.com where scale model Museum quality Yurok Plank Houses are being sold to raise money for the Blue Creek - Ah Pah Traditional Yurok Village project.
Plastering, PM 5, Product & Systems Technology, US Gypsum, May 1998, web search 10.5.2010, original source: http://www.usg.com/rc/technical-articles/plaster/
[copy on file as/interiors/Plastering_USG.pdf ] -
United States Gypsum Company, 125 South Franklin ST., PO Box 806278, Chicago, IL 60680-4124,
Paraphrasing from this document: USG uses the term shadowing in this document in describing the visual effect over gypsum board joints caused by the lower moisture absorption rate (take-up) and lower capacity than gypsum base face paper. Shadowing at joints occurs where veneer plaster is applied over tape joints, requiring a second coat to completely hide the tape, providing a visually uniform surface. USG Advises: "This [second] cover coat must be allowed to harden and dry before plaster application is started.
Plastering Skills, F. Van Den Branden, Thomas L. Hartsell, Amer Technical Pub (July 1, 1985), ISBN-10: 0826906575, ISBN-13: 978-0826906571 [purchase at Amazon.com]
Re-Bath, tub lining products is a bath tub relining manufacturer and distributor located in Tempe, Arizona - see rebath.com
Rubblestone Wall Filler: See this Lartigue House using exterior-exposed rubblestone filler between vertical timbers of a post and beam-framed Canadian building.
Slips, Trips, Missteps and Their Consequences, Second Edition, Gary M. Bakken, H. Harvey Cohen,A. S. Hyde, Jon R. Abele, ISBN-13: 978-1-933264-01-1 or
ISBN 10: 1-933264-01-2,
available from the publisher, Lawyers ^ Judges Publishing Company,Inc., www.lawyersandjudges.com firstname.lastname@example.org and also from the InspectAPedia Bookstore (Amazon.com)
The Stairway Manufacturers' Association, (877) 500-5759, provides a pictorial guide to the stair and railing portion of the International Residential Code. [copy on file as http://www.stairways.org/pdf/2006%20Stair%20IRC%20SCREEN.pdf ] -
Lighting, proper use of: proper aiming of a good flashlight can disclose hard to see but toxic light or white mold colonies on walls.
Manufactured & Modular Homes: Modular Building Systems Association, MBSA, modularhousing.com, is a trade association promoting and providing links to contact modular builders in North America. Also see the Manufactured Home Owners Association, MHOAA, at www.mhoaa.us. The Manufactured Home Owners Association of America is a National Organization dedicated to the protection of the rights of all people living in Manufactured Housing in the United States.
Mold-Resistant Building Practices, advice from an expert on how to prevent mold after a building flood and how to prevent mold growth in buildings by selection of building materials and by anti-mold construction details.
Slips, Trips, Missteps and Their Consequences, Second Edition, Gary M. Bakken, H. Harvey Cohen,A. S. Hyde, Jon R. Abele, ISBN-13: 978-1-933264-01-1 or ISBN 10: 1-933264-01-2, available from the publisher, Lawyers & Judges Publishing Company,Inc., www.lawyersandjudges.com email@example.com and also from the InspectAPedia Bookstore (Amazon.com)
Steps and Stairways, Cleo Baldon & Ib Melchior, Rizzoli, 1989.
Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. Tel: (416) 964-9415 1-800-268-7070 Email: firstname.lastname@example.org. The firm provides professional home inspection services & home inspection education & publications. Alan Carson is a past president of ASHI, the American Society of Home Inspectors. Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The Home Reference Book & illustrations from The Illustrated Home. Carson Dunlop Associates' provides extensive home inspection education and report writing material.
The Illustrated Home illustrates construction details and building components, a reference for owners & inspectors. Special Offer: For a 5% discount on any number of copies of the Illustrated Home purchased as a single order Enter INSPECTAILL in the order payment page "Promo/Redemption" space.
TECHNICAL REFERENCE GUIDE to manufacturer's model and serial number information for heating and cooling equipment, useful for determining the age of heating boilers, furnaces, water heaters is provided by Carson Dunlop, Associates, Toronto - Carson Dunlop Weldon & Associates Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on any number of copies of the Technical Reference Guide purchased as a single order. Just enter INSPECTATRG in the order payment page "Promo/Redemption" space.
The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume.
Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on these courses: Enter INSPECTAHITP in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
The Horizon Software System manages business operations,scheduling, & inspection report writing using Carson Dunlop's knowledge base & color images. The Horizon system runs on always-available cloud-based software for office computers, laptops, tablets, iPad, Android, & other smartphones