OSB (Oriented Strand Board)

A type of roof decking made from compressed wood strands bonded with resin. Less expensive than plywood but more susceptible to moisture damage if exposed.

Why OSB Matters for Insurance Claims

OSB is the most common roof decking material in homes built since the 1990s. Its lower cost made it the default choice for builders, but its vulnerability to moisture means it is more likely to need replacement after a prolonged roof leak. When storm damage allows water to reach the decking, OSB deteriorates faster than plywood. Adjusters should account for this when assessing decking condition, and contractors should document any swollen or delaminated OSB during tear-off for supplement purposes.

OSB in Xactimate Estimates

OSB has its own selector codes in Xactimate, separate from plywood. It is measured in square feet or by sheet count (standard 4x8 sheets). The unit price is lower than plywood, so using the correct code ensures the estimate reflects actual replacement cost. When partial decking replacement is discovered during tear-off, measure the damaged area, photograph it, and submit a supplement with the OSB line items and quantities.

Moisture Vulnerability

The primary weakness of OSB is edge swell when exposed to moisture. Even short-term rain exposure during construction can cause permanent swelling that creates bumps visible through the finished shingles. In claims involving water damage, check the decking from the attic side for discoloration and softness. OSB that has swelled or delaminated cannot be dried back to its original condition and must be replaced, which is a legitimate claim expense when the moisture was caused by a covered peril.