Understanding Water + Wood
Water and wood have a special relationship. Understanding that relationship can make or break the performance of a wood floor.
Manufacturers use an air and/or kiln-drying process to reduce the moisture content in wood before milling it into flooring.
In our homes, wood flooring continues to be effected by moisture in the environment. It gains and loses moisture from the air, if the home environment is not consistently maintained. Palo Duro Vice President Tom Ruekert wrote about relative humidity’s effect on wood flooring on this blog [Read: “ Humidity Matters”].
After wood flooring has been installed, it’s the homeowner’s responsibility to monitor and control relative humidity for the lifetime of the floor. Before and during installation, it’s up to the professional wood flooring installer to get things right.
The industry’s leading resource on this topic is the National Wood Flooring Association (NWFA), which publishes the technical manual, “Water and Wood: How Moisture Affects Wood Flooring.”
What a wood flooring installer needs to know about moisture content:
1. Acceptable amount of moisture content of wood flooring to be installed
2. Acceptable amount of moisture content of the subfloor (plywood or concrete)
3. Relative humidity of the environment leading up to and during installation
An installer should use a moisture meter to take moisture content readings. Before installation, the contractor needs to:
1. Unbundle the wood flooring to be installed and take multiple moisture content readings throughout
2. Take readings of the subfloor in locations throughout the jobsite
3. Document those readings on the subfloor itself, creating a time capsule of proof
4. Take pictures of the moisture meter displaying the moisture content reading, and of the readings written on the floor
If a floor fails due to issues related to moisture, an NWFA Certified Inspector will appreciate the thoroughness of the installer’s attention to moisture content.
The documentation can help to prove the installer did the job correctly, assuming the moisture content readings were accurate and properly used for installation of the flooring.
What Is Proper Moisture Content for Wood Flooring?
Like answers to many questions in life: It depends.
It depends on wood species, geographic location of the end product, and time of year.
Installers should follow manufacturer recommendations. An installer’s second go-to resource should be the NWFA’s Installation Guidelines.
General national averages to follow for moisture content, relative humidity and temperature in an interior environment are:
1. Moisture content should be between six and 10 percent
2. Relative humidity should be between 30 and 50 percent
3. Temperature should be maintained between 60 and 80 degrees Fahrenheit
Effects of Moisture Content in Wood Flooring
Excessive moisture causes wood flooring to expand. That can cause a solid wood floor to crown. Engineered wood flooring can delaminate due to excessive moisture, meaning the top layer separates from the plies of wood beneath.
A more extreme problem due to excessive moisture, for solid and engineered floors, is buckling, which in severe cases also can cause damage to walls.
Too little moisture causes solid wood flooring to shrink. That leads to excessive gapping between boards. Excessive gapping happens unrelated to typical seasonal changes that coincide with outdoor environmental changes.
Engineered wood flooring in an environment with too little moisture can split, check, dry cup or delaminate. To learn more about hardwood flooring, check out the Ultimate Guide to Hardwood Flooring.
Also, visit NWFA at www.nwfa.org, to find more resources on water and wood, and many other wood flooring-related topics.
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