*This article by INSTALL executive director David Gross was originally featured in Floor Covering News.
INSTALLments: A Series on the Challenges & Opportunities in the Floorcovering Trade
Conditioned for Success: Why Proper Acclimation of Wood Flooring Is Essential
Acclimation is a critical step in wood flooring installation that contributes to its long-term stability and performance. Also called conditioning, acclimation is the process that allows wood products to adjust to the temperature and relative humidity of the environment before being installed. When performed properly, acclimation helps mitigate expansion, contraction, warping, and other moisture-related issues that can compromise the integrity of the floor and lead to callbacks. To master moisture concerns and set up every job for success, wood flooring professionals routinely apply the tools and data provided by the United States Department of Agriculture (USDA) Forest Products Laboratory and the National Wood Flooring Association (NWFA) and follow the best practices established by the industry.
Calculating Moisture Content: Regional Averages and EMC Tables
Since wood is a hygroscopic material that absorbs and releases moisture in response to environmental conditions, one important tool for assessing the moisture content (MC) of wood flooring products is the USDA Forest Products Laboratory’s Wood Handbook: Wood As an Engineering Material. This publication includes regional MC data for wood used in interior applications. For example, the average MC in most U.S. regions is 8%, with the southwest averaging 6% MC and warm coastal areas averaging 11% MC. While these measures are helpful, indoor conditions vary and require additional tools for assessment like the NWFA’s Equilibrium Moisture Content (EMC) tables. EMC tables are the standard for wood flooring professionals to calculate the appropriate MC of wood flooring based on the temperature and relative humidity of the installation environment.
Expert Tips for Acclimation and Installation
To achieve optimal moisture conditions and stable, long-lasting wood floor performance, flooring experts at the International Standards & Training Alliance (INSTALL) recommend following these steps:
Prepare the job site. Before delivery, measure and record the temperature, relative humidity, and subfloor moisture content. Make sure the environment meets the manufacturer’s recommended conditions for both the wood flooring and subfloor.
Verify conditions at delivery. Upon flooring delivery, recheck and document job site conditions to confirm they remain within acceptable ranges. Maintain these conditions throughout the acclimation process to prevent fluctuations that could compromise the flooring.
Moisture test. Use a moisture meter set for the correct wood species. Conduct at least 20 readings per 1,000 square feet and an additional four readings per 100 square feet thereafter. Pay close attention to areas prone to moisture, such as exterior walls and plumbing fixtures. Compare readings to NWFA EMC tables and manufacturer specifications to confirm compatibility before installation.
Address moisture issues. If high moisture levels are detected, delay installation and resolve the issue before proceeding. For concrete subfloors, follow the required moisture testing methods for both the flooring and adhesive manufacturer.
Install when conditions are stable. When all measurements confirm the flooring and environment are within the acceptable range, installation can proceed. Note: Storing wood flooring in the installation area for several days does not guarantee proper acclimation—moisture testing is required to verify equilibrium is achieved.
Allow for post-installation conditioning. After installation, allow unfinished wood flooring to stabilize for five to seven days before sanding and finishing. Adhesive-installed flooring may require additional curing time before applying a finish.
Taking the time to test installation conditions, resolve moisture issues, and follow established standards and manufacturer guidelines helps ensure a smooth, successful installation—and a satisfied customer.