Moisture Control in Hardwood Flooring

Essential to any hardwood flooring installation is the importance of properly acclimating your new hardwood flooring. This process allows your new flooring purchase to adapt to your home’s local environment. To achieve this end, we recommend all customers adhere to the NWFA’s guidelines for acclimation. And, there is a distinct difference between how to acclimate a solid wood floor and an engineered one.

In general, solid hardwood flooring takes 10 to 14 days to acclimate. At the end of that period, customers should check the moisture level of the floor so that it’s in the 6-9% range – the average moisture level percent for most regions in America.

For extremely humid or dry climates, customers should refer to the NWFA’s Equilibrium Moisture Content Chart.

No matter where you live, it’s imperative that you acclimate your new floor to your region’s particular environmental conditions.

As far as installation is concerned, when nailing down your new hardwood floor to plywood, the difference in moisture content between the plywood and the flooring should be no more than 2% for boards wider than 2 ¼” and 4% difference for 2 ¼” or narrower. Anything greater than this and you run the risk of potential moisture damage to your flooring.

For engineered wood flooring, be sure to check your manufacturer’s guidelines for specifics on moisture ranges, as these floors are all different.

Also, please note that acclimation time begins only after your home or building’s HVAC system has been running for a minimum of 48 hours and has firmly established the proper environmental conditions for its given space.

Moisture Control Problems

There are several factors that can contribute to moisture control problems in wood floors, as wood absorbs or loses moisture until equilibrium with its surrounding air/environment is achieved. When the moisture content deviates, shrinking, cupping, or even crowning may occur.

Inside climate controlled homes and offices where the air temperature ranges between 60-80 degrees F, ambient conditions typically range anywhere between 35-55% relative humidity. This relative humidity range must be maintained throughout the life of the floor.

Depending on where (and, just as important, when) a hardwood floor is being installed, wood floor installers will have to adjust to different relative humidity conditions. For example, average relative humidity conditions will differ between locales (coastal & inland areas) as well as seasons (winter & summer). Recognizing this is the main reason why acclimation is such an important step when installing hardwood floors.

Regardless of your climate, special care must be taken in order to maintain the required environmental conditions of your home/building as to avoid increasing the tendency for natural wood to swell, warp, crack, or shrink.

Also, keep in mind, when exposed to humidity below 35%, the “top layer” of engineered wood flooring becomes much more susceptible to delamination, cracking, and shrinking; certain wood species (including but not limited to Brazilian Cherry (Jatoba), Brazilian Teak (Cumaru), Brazilian Walnut (Ipe), Santos Mahogany, Tigerwood, Wenge, Douglas Fir, and Hard Maple) especially.

Radiant Heating Floor Systems

Please note, radiant heat can cause delamination, cracking, shrinking, etc. to hardwood flooring. As a result, only certain types of solid and engineered wood floors are designed to handle conditions created as a result of radiant heat.

When installing an engineered or solid wood floor over a radiant heat system, only approved hardwood floors will have a warranty and will require written approval from the flooring manufacturer at the time of purchase and be clearly stated as approved on your invoice from Reserve Hardwood Flooring