Roofing Question.

[Big J Mac]

A roofer said he can remove my shingles to the plywood put new plywood over the old plywood and re-single the roof. Has anybody ever done that or had it done . Pros and cons? Thanks

[1Holeshot]

I suppose if the fasteners were long enough that would work.

[Southern Hunter]

Makes no sense as to why you would double up the plywood…? If there is rotten plywood, change it. Otherwise tear shingles and underlayment/felt off to the plywood decking, then re-apply underlayment/felt and shingles.

[BP in ME]

Makes no sense as to why you would double up the plywood…? If there is rotten plywood, change it. Otherwise tear shingles and underlayment/felt off to the plywood decking, then re-apply underlayment/felt and shingles.

Would be interesting to hear the reasoning. Is he wanting to lay 3/8" over everything because there's soft spots?

[Big J Mac]

He said if he finds a bad board he will pull it off and replace it with a new one then over lay the whole roof with new plywood he said it will make the roof stronger. If I want to pull all the old wood off it will cost extra.

[rednecktech]

Sounds like a way to inflate his profit for some unnecessary work. I have seen shingles put on top of existing shingles, but never doubling up the decking.

[A.MAC]

I’ve had our crews do this before. Taking an entire roof deck off would be difficult and could lead to problems with rafters moving. I’ve done this when thin plywood was used initially and going on top with thinker plywood solves the problem. He’ll have to use larger drip edge to compensate for the extra plywood so it comes down on the fascia the same place the old drip edge did. If this isn’t done you might have to touch up your paint.

[triton]

Thats the dumbest thing I've ever heard, replace the board that needs to be replaced and
lay your shingles...

[Doorman1]

Had it done to a roof in 2002 the plywood didn’t have any rot but the glue in the original plywood was starting to fail. Don’t know how it’s lasted since I sold that house a year later.

[vaw121]

I've heard of this in cases where a home has had several shingle replacements. Is it possible your wood has many nail holes in it now?

[Big J Mac]

The cost difference to put all new plywood over the old is 1000 dollars for a little under 32 sq of roofing I didn’t think that was to bad? I just never Heard, of it done this way before he said a lot of Insurance companies are doing this. I don’t know guys, I’m just trying to get some opinions before I pull the trigger. Thanks

[plbass]

Get other quotes and compare. If they don't mention adding plywood then ask them if there is a reason to do so. Never heard of a roofer adding plywood for no reason.

[Crappie Bob]

I would get another roofers opinion that does not know the roofer you have, a lot are in with each other these days. If the roof needed two sheets to be stronger it would be by building codes. If you have extra layers of anything on your roof and it needs to be repaired, they charge extra for removing the extra layer down the road. If too many nail holes are a concern, inquire about Peel & Stick over the entire roof.

[krindgen]

Poor, labor saving approach. Doubling the sheathing load too.

[mactlman]

roofer had to put thin layer of plywood on dads roof when he had it done. the original wood was dried out from lack of ventilation and would not hold nails correctly. likely what you have going on.

[ericm]

That’s a bad idea. First they’re adding needless dead load, second, if you do develop a leak in the future you’ll trap water between the the two layers and that’s when your real problems will start. They should strip down to exit deck and remove/ replace any deteriorated sheets. Make sure they include ice / snow membrane 3’-0” past the inside face of walls

[wareagle24]

He said if he finds a bad board he will pull it off and replace it with a new one then over lay the whole roof with new plywood he said it will make the roof stronger. If I want to pull all the old wood off it will cost extra.

That's alot of unnecessary weight on your roof by doubling it up.

My question is this. I can see replacing the damaged wood but why in the world would he want to tear off good plywood and replace it? That makes zero sense to me. I would call another roofer or two.

Also the math just don't add up. Keep in mind I'm just talking rough figures here. 32 squares of shingles covers 3,200 square feet. It would take 100 pieces of plywood to cover the same 3,200 square feet. You can't buy 100 pieces of plywood for a 1,000 dollars much less put it on at that price.

[paulrodbender]

Common up here on older homes where boards where used before plywood was invented. After time the board spacing increases and you have the risk of nailing shingles to the gap’s instead of wood.

[Big J Mac]

I think his biggest concern in the wood up there is thin and getting weaker over the years. I have been up on the roof and it will flex when you walk on it but looking at the roof from the ground you don’t see it sagging between the rafters. I did get two other estimates and they where 3 and 4 thousand more then this guy. That’s why I reached out to BBC about the way he is wanting overlay this wood.

[wareagle24]

I think his biggest concern in the wood up there is thin and getting weaker over the years. I have been up on the roof and it will flex when you walk on it but looking at the roof from the ground you don’t see it sagging between the rafters. I did get two other estimates and they where 3 and 4 thousand more then this guy. That’s why I reached out to BBC about the way he is wanting overlay this wood.

Did you get written estimates from these roofers? Also is he going to use actual plywood instead of OSB? What thickness did he say he was going to put down? Don't assume anything.