Moisture is a subtle culprit of hardwood floor damage.
This is because wood absorbs and releases moisture to match the moisture level of its environment (the equilibrium moisture content, or EMC). If the wood floorboards don’t match the moisture level of the environment before installation, they will absorb or release moisture after installation. This causes shrinkage or expansion, resulting in cupping, warping, buckling, or unsightly gaps.
The next thing you know, you have frustrated customers who are doubting the quality of your work. So, how can you avoid this scenario?
It’s all about proper moisture testing. Some simple steps can prevent moisture damage to your hard work and your customers’ investment. Let’s look at these steps, based on recommendations from the National Wood Flooring Association (NWFA).
Check Environmental Conditions
Before bringing installation materials to the jobsite, be sure the temperature and relative humidity are at in-service levels. The industry standard is usually somewhere between 60° and 80° F and 30 and 50 percent relative humidity (though the floor manufacturer may offer a more-specific range).
Per the NWFA, these conditions should be consistent for at least five days before the building materials arrive. A permanent or temporary HVAC system should be up and running to achieve those levels.¹
How do you know for sure that conditions have been consistent for this long? One handy way is to leave a temperature and relative humidity logging device (data logger) at the jobsite and then check it before you begin work.
Determine the Equilibrium Moisture Content (EMC)
Two main factors affect EMC: the relative humidity and temperature of the final environment that will be surrounding the floor. Once you know environmental conditions are consistent, you can use those numbers to calculate the moisture content the floorboards will need to reach.
One way to do this is to use an EMC chart. Or better yet, find a wood moisture meter or an app that automatically calculates the EMC for you.
Test the Subfloor for Moisture
The subfloor can transfer moisture to the floor and damage it.
If the subfloor is wood, use a wood moisture meter to test 20 areas for every 1,000 square feet or a minimum of three tests per room. Then, average the results.² The subfloor’s moisture levels should be within 2 percent for plank or 4 percent for strip flooring.
Note the locations of especially high or low readings. They could be indicators of leaks or other moisture problems that need to be addressed before a floor can be installed over top.
If you’re dealing with a concrete subfloor, the relative humidity test (ASTM F2170) and the calcium chloride test (ASTM 1869) are common test methods.
There may be times when a concrete moisture meter would be the more-practical option. ASTM F2659, the standard for these meters, does not yet recognize their use as a final determiner of moisture levels, but some manufacturers do allow them.
Acclimate and Test Flooring Materials
When you bring the hardwood floor materials to the jobsite, scan them with a moisture meter, checking 40 boards for every 1,000 square feet of flooring. Any unusually high or low moisture readings should be isolated and not installed in the floor.³
In general, the moisture readings should fall between 6 and 9 percent, though the expected EMC is ultimately the number you’ll want to use as your target.
If the boards aren’t at the EMC, the NWFA recommends that you “cross stack the materials with spacers (¾-inch to 1-inch stickers) between each layer of flooring to allow air circulation on all sides.”4
Continue to test the boards until they’ve reached the EMC and are in alignment with the subfloor MC levels.5
A pinless meter allows you to quickly scan a large quantity of boards without leaving pinholes. When using pin meters, stick the boards on the back to avoid damage to the face of the material. Be sure the meter is calibrated and adjusted for the right wood species.
Document Test Results
As you test the materials for moisture, be sure to record the date, time, and readings. This way, you can show customers you did your due diligence, and you’ll avoid being blamed for issues you didn’t cause.
Install a Wood Floor Data Logger
For an added measure of assurance, consider including wood floor data loggers as part of your flooring package. These small loggers, installed on the underside of floor planks, keep track of the temperature and relative humidity of both the floor and subfloor.
The loggers have Bluetooth capability, so customers can view the data on their smartphones and receive alerts if moisture levels go out of range. This way, you’re equipping your customers to care for their own hardwood floors. Think of it like cheap flooring insurance to protect your work and reputation.
Give Your Customers a Long-Lasting Floor
Unmanaged moisture can cut short the lifespan of a hardwood floor you’ve installed. What’s more, the damage may affect a customer’s view of your reliability. Even if everything else was done perfectly.
Thankfully, it doesn’t have to be that way. Testing for and managing moisture during your installation process can give you the assurance of a damage-free floor. That’s peace of mind for you and your customer.
SOURCES: 1 Moisture and Wood, NWFA, p. 14; 2 Ibid., p. 20; 3 Ibid., p. 14; 4 Ibid; 5 Ibid.
Jason Wright is the business development specialist for new products for Wagner Meters. He brings more than 30 years of flooring industry experience with particular specialization in hardwood floor products and installation. Beginning in 1986, with a small sundry distributor in Medford, Oregon, Wright ascended through positions in regional sales, product development, business development, and marketing programs within different flooring companies. He can be reached at jwright@wagnermeters.com. For more on moisture testing during floor installation, visit wagnermeters.com.