Making Sub-Floors More Moisture-Resistant

There are many areas of the United States where homebuilders must deal with significant rain volume and rain duration. For example, Miami and New Orleans each get more than 60 inches of rain every year, but it falls in just an average of 56 days. In contrast, Portland and Seattle average around 40 inches of rainfall annually, but it stretches out over 154 days per year. 

It's important for the sub-flooring in new homes to handle heavy rain volume, but it must also have sufficient time to dry during periods of intermittent drizzle. That's why moisture resistance is one of the most important design features of sub-flooring. It's a benefit that's just as important as strength, stiffness and easy installation.

Here are some of the ways manufacturers are making sub-flooring products more moisture-resistant:

Rain drainage features – LP^® TopNotch^® 350 sub-flooring was the first in the industry to offer a patented notch system cut into the panels to help drain rainwater away during construction.

Innovative use of resins – Some sub-flooring is made from rectangular wood strands blended with thermal-set, waterproof resins that are arranged in cross-directional layers and bonded together under extreme pressure.

Edge sealant – Builders can easily find sub-flooring panels where moisture-resistant edge sealant has been applied during manufacturing.

Long-term no-sand warranties – Some sub-flooring panels are surface sanded during the manufacturing process, and builders can often take advantage of no-sand warranties that last three months or more. This gives sub-flooring ample time to dry without additional sanding, even in areas with frequent rainfall.

Whether sub-flooring products are being installed in rainy Portland or Yuma, Arizona (where average rainfall is less than four inches per year), they need to be certified by the Engineered Wood Association (APA) and provide performance categories from 19/32˝ to 1-1/8˝. But it's also important for sub-flooring products to offer the moisture-resistant features outlined above to ensure that they'll deliver maximum strength and stiffness for years to come.