OSB Plywood

DEAR TIM:  My builder insists that 5/8" OSB plywood is fine for the roof. The OSB board got wet after one significant rainstorm before the shingles were able to be put on. Do you think that we will have any problems with our OSB sheathing roof? James K., Northwest PA

DEAR JAMES: The OSB board on your roof should be just fine. This engineered wood product is made to get wet. The lumber mills realize it's impossible for houses to be constructed in consistently dry weather.

OSB sheathing does much better getting wet than OSB subflooring. You can get swelling with OSB subflooring that puffs up the material. But roofs and sidewalls that have OSB board dry much faster than sheets that are laying horizontally on the floor.

If at all possible, allow the OSB plywood to dry thoroughly before the roofer applies the underlayment. It doesn't take long for the OSB roof sheathing to dry in most situations. A little breeze and some sun can dry the roof sheathing in hours.

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