It is a common theme with wood flooring–that when things go wrong it is most often related to moisture. The best way to avoid moisture-related problems is in proper job site preparation.
Always acclimate solid hardwood flooring to the home’s living conditions before installing even one board. Acclimation of traditional 3/4 inch solid hardwood, either unfinished or factory prefinished, is critical to the successful performance of the floor.
Installing an engineered floor? Solid and engineered wood flooring have different acclimation requirements.
If installing engineered hardwood flooring, follow the manufacturer’s instructions included with the flooring. Get more tips for acclimating engineered wood floors here.
Why Acclimate Solid Wood Flooring?
It is important to acclimate solid hardwood because wood is hygroscopic. This means that it will absorb and release moisture with its surrounding environment.
Taking on or losing too much moisture will result in dimensional changes in the wood floor. It can expand, shrink, cup, check, or split because of excessive moisture changes.
When wood flooring is exposed to excess moisture individual boards can start to expand. These boards can exhibit a cupped or swollen appearance that can put pressure on the fasteners that hold the floor down resulting in squeaks or loose flooring.
When flooring is glued down, excess moisture can cause the wood to stretch the adhesive beyond its maximum tensile strength resulting in adhesive failure. When flooring loses moisture and becomes too dry, boards will begin to shrink in width, resulting in gaps between boards. Flooring boards may also bow or crown in the center because of the board edges becoming too dry.
It is essential for the relative humidity inside to be properly adjusted before the floor is installed. If indoor humidity dramatically changes once the floor is installed, there is a greater chance the flooring will be affected and damage occur.
Properly Acclimate Solid Wood Flooring
Now that we’ve established why acclimation is important, it is equally as important how to acclimate solid wood floor. Watch our Wood Flooring Acclimation 101 video to see each step involved in the process or continue reading for a text summary.
**Please note that these tips are not for engineered wood flooring. Engineered wood flooring has different acclimation requirements. Follow the flooring manufacturer’s recommendations to properly acclimate an engineered wood floor or get more tips here for acclimating engineered wood floors.
Step 1: Climate Control the Home for 2 Weeks Prior to Delivery
Proper acclimation starts right after delivery to the job site. So, before bringing any wood flooring to the installation location check the environmental conditions of each room where the flooring will be acclimated. Use a thermo-hygrometer to record both temperature and relative humidity.
Proper acclimation of flooring is about consistent climate control of the home. It is recommended that for at least two weeks prior to delivery, home should be operating under normal living conditions in preparation for the flooring to properly acclimate.
Step 2: Measure the Moisture Content After Delivery
When installing unfinished wood flooring, bundles of flooring can be delivered into the home and cross-stacked as in step 3 of the video.
For prefinished flooring, each box of flooring can be opened along the tape seam lengthwise and at the ends of the box. Be sure to open and remove the inner plastic wrapping as the flooring will not properly acclimate if left in the plastic.
Will hardwood flooring acclimate in the box? Not unless they are opened. Boxes must be opened along the seams and the plastic removed for best results. Dry-fit a few boards together to ensure proper fit and finish and verify color and species with the homeowner.
The installer is the final inspector of the floor. It is always best to catch problems before the floor is delivered and installed.
After approval, set your moisture meter to the correct species setting for the flooring being tested. You’ll find this setting in the moisture meter’s operating manual.
Measure the moisture content of several boards, across several boxes of flooring. Also, measure the moisture content of the subfloor, remembering to adjust the species setting on your meter. Usually, a subfloor with a moisture content of less than 12% is ready to work on.
However, note that in most cases, the moisture content of the subfloor and flooring must be within 2% of each other to begin the installation. The exception is for very narrow solid flooring and engineered flooring.
Step 3: Cross Stack All The Boxes
Continue bringing in boxes of flooring and spacing them apart, so that one holds down the cardboard flap of the other. Open the cardboard flap and plastic wrapping of every box and remove for best results.
Cross stack the boxes or spread throughout the home so that air can circulate throughout the flooring. This will allow for the most efficient acclimation.
If you need to return a full unused box, simply fold the cardboard flaps together and tape with clear packing tape. We cannot accept returns of unused boxes unless they are packaged and taped and in their original condition.
Step 4: Determine When It’s Acclimated
Once you have completed steps 1-3, how do you know when the flooring is finally acclimated?
There is some complex science behind the answer to this question.
Simply stated: wood flooring has acclimated once it has reached equilibrium with the home kept at average normal living conditions.
Determining when the floor is in equilibrium requires good judgment based on factual readings, experience, and the climate conditions of your geographic region.
Ask yourself the following questions:
- Has the home been climate controlled for a minimum of two weeks?
- Is your flooring within 2% of the subfloor?
- Is the moisture content of the flooring within the range for the geographic region and the conditions of your home? See the chart below for the acceptable range.
For example, in a Northern climate, home’s without a humidifier could see flooring dry out to as low as 5% moisture content. If the home has air conditioning, the upper range might be 9% in the summer. Therefore, the average moisture content for wood to be installed in this climate would be around 7%.
This following table shows the relationship between temperature and relative humidity in the home and the % moisture content allowed in the wood flooring.
If the home is kept at 70 degrees Fahrenheit with the relative humidity at 40%, the wood will be in equilibrium with the home at 7.7% percent moisture content. If the temperature remains the same, but the humidity dropped to 25%, the wood will dry out to 5.4% moisture content causing the flooring to shrink.
This is why some seasonal expansion and contraction of flooring is considered normal, even when gaps or slight cupping appear. These issues can only be minimized by proper acclimation and keeping the home at a consistent humidity and temperature. Humidity or temperature changes in the home will cause a change in the flooring.
How to have a successful acclimation every time
The rule to remember is this: Achieving and maintaining a constant temperature and humidity will result in the best acclimation and long-term success every time.
Accomplishing this will prevent movement and stresses on the glue or fasteners and the flooring itself. Wood flooring loves constancy!
Always fully acclimate before installation to keep your floor as stable as possible. Know how to use your moisture meter and buy a quality one. Most climates will need a central humidifier or dehumidifier in the home to keep humidity levels consistent.
Dry heat from a wood-burning stove along with the arid winter climate will cause wood flooring to lose moisture rapidly. Conversely, opening windows in the mild seasons or not running A/C on hot humid days will also cause wood floors to expand and cup due to excess moisture.
Wood is a living, breathing material that has been used as flooring for hundreds of years. When properly installed and maintained, will last a lifetime.