Engineered Wood Flooring and Indoor Humidity


The proper level of indoor relative humidity (RH) is a moving target based mainly on the outdoor temperature. The lower the outdoor temperature, the lower your indoor RH% should be. This is to prevent condensation from forming on your windows and in your walls. An example would be a glass of your favorite beverage with and without ice in it. Without ice, the beverage is warmer and the outside of your glass stays dry. When you add ice to chill it, the outside surface of the glass is cold and begins to sweat. Unless you have a coaster, you get water all over the surface it’s sitting on, which can ruin it.

Most manufacturers of engineered wood flooring require humidity levels between 35-55%. BEWARE: If humidity levels are above, or below the manufacturers specifications, the manufacturer may not honor the warranty.

In most areas of the country humidity levels cannot be maintained over 35% once the outdoor temperature drops below 20F, and building experts warn against higher humidity levels because the excess moisture causes damage to the building. The chart below, referenced from Aprilaire outlines recommended indoor humidity according to outdoor temperatures.

If an engineered wood floor is specifically designed for conditions other than those that will be encountered at the job-site, then selecting another product suitable to the conditions should be considered.

Proper Indoor Humidity

During the heating season the average American home (unhumidified) may have a relative humidity (RH) as low as 13%. That depends on outside temperatures, as indicated here:


Locate outdoor RH at the left of the chart and the outdoor temperature at the bottom. Your indoor RH is where the vertical and horizontal columns meet. This chart assumes that outdoor air is brought into the home and heated to 70°F.