Water And Wood

A heavy moisture invasion can seep up through a

wood subfloor. It may occur slowly, but its effects are

damaging. Proper installation of flooring calls for

checking subfloors for moisture.

To protect against moisture rising through subfloors,

the installer needs to make sure there is a

proper moisture-vapor retarder.

In any case, the moisture content of solid strip flooring

should be within 4 percentage points of the subfloor.

(That is, if the subfloor is measured at 10 percent

moisture content, the strip flooring should have no less

than 6 percent moisture content and no more than 14

percent.) For solid plank flooring, the difference should

be no more than 2 percentage points. Solid strip or

plank flooring requires a felt paper moisture retarder

between the floor and subfloor. If a wood subfloor is

laid over an existing slab, the moisture retarder can

be cemented to smooth, clean-swept concrete.