The old farm house is needing a new roof. The place is over eighty years old. Some of the farmers before me were thrifty.
In the beginning wood was cheap. I suspect the place was originally shingled with shingles from shingle oaks. But then somebody decided to switch to ashpahlt.
Well being thrifty they did not tear off the old purlins and put on a plywood deck. They filled the gaps between the purlins with more oak from the sawmill. So underneath it looks like oak 1 x 6 from top to bottom. Rafters are 24″ on center.
Will a pneumatic nail gun drive a 1″ roofing nail in old oak? It takes hardened steel to nail in the barn.
If no, then should I tear it off to the rafters and put on a new deck? Or could I lay the plywood over the existing deck? What do you think 7/16 OSB, 1/2″ plywood or thicker?
Replies
Any decent nail gun should have no trouble shooting one-inchers into pretty much anything short of concrete or steel. You could probably also use an HT-65 hammer stapler; these are routinely used in crate assembly lines where oak is commonly encountered.
As far as adding a new deck on top of the existing one, if you do that, you'll still have to nail (or screw) it in place, so you're no further ahead, seems to me.
If you strip to the rafters and lay on a new deck, IN NO CASE should you even consider laying 7/16 OSB on 24" centers, nor even ½" plywood, unless the slope is over 10 in 12. You need a minimum of 5/8", and I wouldn't use OSB on any low slope application at all.
Dinosaur
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What we do often with the old ones is to overlay the sheathing with 3/8" plywood or with 7/16" osb more to propvide a smooth firm surface under the asphalts than anything else. Splits, checks, loose knots, and gaps between boards can play havoc with them and shorten their lives. With sheathing as hard ads yours, you'd need to screw it down and you should try to do it a the rafters with structural deck screws and not with sheet rock screws.
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I'm with Piffin on this one -
Strip it off to the boards, and put down 7/16 OSB.
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