An increasing number of homes and light commercial buildings have oriented strand board (OSB) subfloors. Builders choose OSB because it typically costs less than plywood, is free of knots and voids, and can be used interchangeably in typical flooring applications where the panels have the correct span rating. It provides a flat, solid base for any floor covering and can aid in the creation of even, stable and long-lasting floor finishes. But, as with other wood substrates, proper moisture management is essential for a quality installation-especially in regards to hardwood flooring.
In the event the moisture differential between the OSB and hardwood is too great at the time of installation, problems can arise. OSB that has absorbed moisture on the jobsite shrinks as it dries, which can loosen around nails and staples that attach the hardwood flooring. This can result in squeaks and pops when occupants walk across the finished floor. Additionally, wet OSB under drier hardwood flooring can cause moisture to migrate into the hardwood and result in cupped flooring. If the hardwood flooring is installed with excess moisture, it can shrink and create gaps.