Understanding Acclimation is Crucial in Preventing Wood Floor Failure
September 30, 2002
A frequently asked question regarding the installation of wood flooring is: "How long does it take to properly acclimate wood flooring before installation?" Acclimation depends on the type of wood flooring product, job site, local environment and any special conditions imposed on the application. First, always read the manufacturer's instructions. Most solid strip and plank products require some form of acclimation. Some special proprietary products may not. Generally, thicker, solid parquets will also require acclimation, whereas thinner materials such as 5/16-inch "fingerblock" do not. Engineered products generally do not require acclimation. The pre-installation jobsite conditions must be near occupancy levels as a beginning step in proper installation and acclimation. Jobsite conditions that are too wet or too dry during acclimation of the flooring prior to installation will result in less-than-optimum performance and possible callbacks or failures later. The installer/contractor should also know the expected environmental conditions during both winter (dry season) and summer (wet season) to determine a base line for proper acclimation. A moisture meter is an essential tool in determining present conditions. The moisture meter can also determine when necessary acclimation has been accomplished.
It is always important to determine a starting condition and establish an ending condition for proper acclimation of the flooring. Begin by checking the conditions of jobsite materials with a moisture meter. Take 20 to 40 readings of subflooring and other wood materials such as doorframes, exposed studs, etc. installed at the site. Write down and average the readings. Readings should have a fairly narrow overall range, about 3 percent. If a couple of readings are significantly higher and they are random, no problem is indicated. However, check the area if two or more readings are outside the 3 percent range. A significantly wider range indicates the proper jobsite environment has not been properly established and is probably not at recommended levels. These readings determine the base line condition of the jobsite. These moisture conditions should also be within the overall range expected for the area. Flooring should not be delivered to the site if unfavorable conditions exist. Next check the flooring by taking 20 to 40 readings; write the readings down and calculate their average. This gives a base line for the flooring. The readings should also have a fairly narrow range (3 percent). An occasional errant reading is generally not a problem indicator. Where the average of these readings is different by more than 4 percent from the average area environmental condition, acclimation is generally necessary. Acclimation is accomplished by exposing the flooring to the proper conditions. Opening packaging, distributing bundles, and racking the flooring all help this process. When the 20 to 40 moisture checks average within the average area environmental range, the flooring is acclimated to the area and is ready for installation. An example of the acclimation process follows. For Memphis, Tenn., the winter conditions are near 7-8 percent moisture content (m.c.) and summer conditions near 9-10 percent m.c. for an average of 8.5 percent m.c. Ideally flooring should be near 8.5 percent when installed. If flooring averages 6.5 percent m.c., it should be acclimated before installation. When the average moisture condition of the subflooring and other jobsite materials is 12.5 percent m.c. or less (no more than 4 percent different from the average conditions), the site is suitable for installation. For flooring delivered in the winter, acclimation to higher than 7 percent m.c. may not occur. In this case, expansion gaps (washer rows) placed in the field during installation may be necessary to accommodate the expected summer expansion and prevent cupping associated with this expansion. Wood flooring will acclimate to its imposed environment. For unfinished solid wood strip and plank flooring, allowing time (1 to 3 weeks) after installation for acclimation is recommended. The strips are in place and equally exposed so those with higher m.c. will lose moisture and those with lower m.c. will gain moisture. The resulting flooring conditions will be taken care of as sanding and finishing are completed. Acclimation is critical during remodeling applications and when using factory finished flooring because accelerated schedules are often demanded. Acclimation off site may be necessary is these cases. For these applications, the jobsite is generally well established with conditions of an occupied environment. Checking the site m.c. and acclimating to this condition is the key to avoiding callbacks. A professional flooring contractor should have and use a moisture meter, take a sufficient number of readings, average the readings, and know the environmental conditions of the area. The contractor should make decisions regarding acclimation and installation based on the obtained data. Just looking at the job and placing flooring at the site for four days without the proper qualifying information is like rolling the dice: sometimes you just roll craps.