What is the recommended condition for subsurfaces below hardwood flooring to be considered dry?

The correct condition for subsurfaces below hardwood flooring to be considered dry is described as being within 2-4 percentage points of the moisture content typically found in hardwood. This standard acknowledges that hardwood can naturally absorb some moisture from its environment, and a small range above its standard moisture content is acceptable to ensure that the flooring itself remains stable, functional, and free of issues such as warping or cupping.

Maintaining this recommended range helps to ensure that the flooring does not initiate or contribute to mold growth or deterioration, which can occur if the subsurface moisture is too high. It provides a balance between the natural properties of hardwood and the need for a safe and healthy indoor environment.

While other options may reference specific moisture content levels or conditions, they either do not align with accepted industry standards or imply a more stringent condition than what is typically deemed necessary for maintaining the integrity of hardwood flooring installations.