Cupping, as shown in this gymnasium floor, is one of the most common results of excess moisture in hardwood floors. Photo courtesy of the National Wood Flooring Association.

Ask any wood flooring contractor what the number one problem he or she encounters on the job is, and most will answer “moisture.” Excess moisture can cause a variety of problems with wood floors, whether the moisture originates from an environmental source, or from a flood caused by a malfunctioning appliance or unattended window. Whatever the source of the problem, however, dealing with the results of excessive moisture in wood floors requires diligence and skill.

In most cases, moisture problems can be avoided before they occur by practicing good installation procedures. The first step in a successful installation is to make sure that the wood to be installed is acclimated to the job site properly. This means that the job site needs to be as close to normal living conditions as possible before installation begins. If the installation will take place during the winter months, chances are the heating system will be turned on, and that the job site will be sealed tight. This situation typically causes the job site to have drier than normal living conditions.

Conversely, if the installation will take place during the summer months, chances are that the air conditioning system will be turned on, and that the job site will be exposed to environmental elements more readily. This situation typically causes the job site to have wetter than normal living conditions. As a general rule, the goal is that the relative humidity of the job site should be within the range of the yearly average for the geographic area. Extreme variations on one side or the other will cause problems down the road.

Once the wood is acclimated properly to the job site, it should be tested thoroughly, along with the subfloor, for moisture content. To get accurate readings, several different pieces of wood from several different bundles should be tested. If the average moisture content in the wood is 8%, and the relative humidity is 45%, the flooring is acclimated to the environment, and should remain on the job site until installation begins.

Often, anxious homeowners or builders will try to push wood flooring installers to skip this acclimation process because of scheduling problems. Contractors need to be firm, and educate their customers about how wood reacts to environmental conditions. It often is useful to keep pictures on hand that show the results of improper acclimation and moisture testing. One look at a cupped or crowned floor, representing thousands of wasted dollars, and weeks of messy and costly repair, is often all that is needed to make the point loud and clear.

Sometimes, despite all the installation precautions taken, moisture still can wreak havoc on a wood floor. Faulty dishwashers, overflowing sinks, leaky pipes, malfunctioning ice makers, careless homeowners – all these problems can introduce moisture to wood floors, causing significant damage if ignored and untreated.

The most important step in repairing the damage is to first find the source of the problem and eliminate it. This sometimes is not as easy as it sounds. Often, moisture sources develop over time, and the source may not be obvious. For example, perhaps a kitchen was remodeled several months ago, and during construction, a water line was punctured slightly and the contractor did not notice it at the time. A slow leak might take months to cause noticeable damage to wood floors, and it may not be obvious where the leak is originating. In this case, take moisture readings near the area where the damage is obvious, as well as surrounding flooring or walls where damage is not obvious. This often can save significant time, and expense, in locating the source of the damage.

If the source of the damage is obvious, say perhaps a dishwasher has malfunctioned and flooded the entire floor, the water must be removed immediately. Next, introduce fans and dehumidifiers to the damaged area to increase air circulation and reduce humidity levels. If you can access the floor from below, from a basement for example, place fans there as well. This will help to further increase air circulation. Finally, turn the heating system on to help drive the humidity down. A temperature between 76 and 80 degrees is ideal.

Once all these procedures are in place, adequate time must be taken to allow the floor to completely dry and resettle, or flatten out. If the repair starts while the floors still are slightly wet and cupped, they may crown, creating a new problem, when they do dry adequately. As a general rule, it will take at least a week for the floors to be ready for repair.

Before any repair begins, be sure to take moisture readings from several areas in the floor, and make sure all areas are within normal ranges. Once readings are in the normal range, the action for repair can be determined. If the floor still appears to be cupped or buckled, it will need to be removed and replaced. If the damage is minor, sanding and refinishing the floor will most likely be adequate to restore the floor to its original beauty.

The National Wood Flooring Association has detailed guidelines available about moisture testing procedures and repair of damaged wood floors. The NWFA is an international not-for-profit trade association of wood flooring professionals, dedicated to advancing the wood flooring industry and its members. For more information, contact the NWFA in the USA at 800-422-4556; in Canada at 800-848-8824; and in international locations at 636-519-9663; or