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tns1 10-30-2009 05:51 PM

new sheathing on top of old?
When I redo my asphalt shingle roof, I'll be stripping it first, and then I'll need to replace an unknown amount of sheething. If it turns out that most of it needs to be replaced, would I be advised to remove all of the old stuff or layer on top?

jogr 10-30-2009 06:13 PM

I'd remove the bad to make sure the deck is fllat and secure.

tns1 10-31-2009 01:19 PM

I guess what I was wondering is if layering new osb on top of my existing plywood would even be permissible from a load standpoint. Are the load calcs based on what the framing will bear or just what the sheething will bear?

BamBamm5144 10-31-2009 06:48 PM

You will have to check with your local building codes. From an added weight standpoint, I would assume it to be against codes. I have never done it like that but I usually rather do things right the first time.

Slyfox 11-01-2009 07:31 AM

If you replace any bad / rotted sheathing with the same type,
than cover over all with a lighter weight / thickness you should be fine.

But that's assuming there's no structural damage, bad trusses, etc.

You do not want to cover rotted lumber with new tho.

ausblake 11-01-2009 11:28 AM

Agree with Slyfox. You never cover bad wood with good wood. Tear up the bad and replace.

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