For those of you with a crawl space, it’s time to make a trip outside. Fully inspect the ground beneath your home to assess the moisture content of the soil. Do you have any areas that are wet or any pools of water? If you have either of these issues, you must correct these before you can move forward with your hardwood installation. Not addressing problems such as these before you install the hardwood can result in cupping later on, which is a condition caused by the wood remaining damp on the underside but not on the top.
Once all problems are corrected, most manufacturers suggest that all crawl spaces have no less than a 6 mil polyethylene plastic sheeting placed on the ground beneath the house to prevent the wood being affected by the natural ground moisture. Many newer homes will already have these due to building codes, but if your home is older chances are you do not have one.
Homes with concrete foundations will undergo a different battery of pre-installation tests in regards to the foundation. Concrete is mixed and placed with the requirement of water, and this also must escape as the concrete ages. How rapidly this occurs is determined largely by vapor pressure in both the slab and the air over the slab, as well as conditions below the slab.
Make sure your installer performs these tests before installation begins:
Perform a moisture test on concrete slabs by taping 7-10 18″x18″ pieces of plastic to your subfloor in different areas. Wait a period of at least 18 hours, and if condensation develops, you will need to take steps to seal your concrete before installation. Another way to test the slab is to use a moisture meter, which is available for purchase at most any hardware store. (Acceptable moisture levels are 14% or less)
Other tests to be performed by the installer are:
Calcium Chloride – Should not exceed 3 lbs per 24 hrs per 1000 square feet of area
Radiant Heating Calcium Chloride – Should not exceed 1.5 lbs per 24 hrs per 1000 square feet of area.
pH reading of the slab–An acceptable pH reading is between 6–9 on the pH scale.
DO NOT INSTALL your hardwood floor on a concrete slab if you receive high readings on your Calcium Chloride and pH test. You will need to purchase a specific sealer in order to correct the humidity and calcium levels within your concrete slab.
Testing your hardwood and home climate
Wood flooring will perform best when the interior environment of your home is controlled with a relative humidity between 30-50 percent and the temperature 60-80 degrees Fahrenheit. Outside of these ranges, wood can dramatically shrink or expand and can cause permanent damage to your home. Relative humidity meters are available at most any hardware store for very little money, so take the time to pick one up before installation day.
The final test to make sure is done before installation, is to test the moisture in your pre-acclimated wood. Again your installer should have a moisture meter to measure this. The wood itself must be between 6 and 9 percent moisture and no more on the inside. If the wood has not acclimated and is higher or lower (while stored inside your home) to this percentage, you will need to wait until it reaches the required percentage.
One final note: Some cupping and crowning is a natural part of ownership of hardwood, and not all cases indicate issues with your home.
For more information, please visit The National Wood Flooring Association’s web site.