Tim:
I was also concerned when I saw OSB being used on my house when it was
being built. As an experiment I put a cutoff into a 5 gal bucket of water
on the jobsite to see how it would hold up. I removed it from the water
about 1 month later and let it dry in the sun. It did not warp nor did it
swell. I am convinced that there is more resin in the product than wood.
I did notice that even without being soaked the edges of cutoffs chip off
splinters very easily. It has more integrity when it is whole than after
it is cut.
OSB Plywood
Summary: Can wet OSB plywood be used for roofing? Roofing materials, such as osb or plywood, can get wet during construction.
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 Katzin, Emlenton, 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 horizontal on the floor.
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 horizontal 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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Comments:
Denny Mela 08 Jan 2009, 12:49
Bruce Atwood 20 May 2009, 17:53
I am about to purchase a house in New Hampshire that was a shell for 8-10
years. Roofing was on, and I think windows.
Is the sheathing OK? Or is it apt to be weakened by exposure to the weather? Thanks
Amanda Holthaus-Little 29 May 2009, 07:36
My husband and I are about to buy a home and while in the attic we noticed
that some of the plywood underlayment was just plain crumbling in certain
areas (by the chimney and by the eaves of the house). The previous owners
said they had "updated" the roof. Is it normal to lay a new roof on top of
the old plywood? Is this a potential problem? Is there another layer of
plywood that would have been added over the old? I know it's impossible to
know without seeing, but what is the common practice?
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