Does Plywood sheathing HAVE to be removed?


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Old 09-18-07, 07:37 AM
J
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Does Plywood sheathing HAVE to be removed?

Hello,

Its common for contractors to say, "you can put one layer of asphalt shingles over another, but then you have to do a complete tear-off and put down new plywood."

But I never asked "Why?"

If the 40 year old plywood is in good shape, why should we have to replace it? Why not just tear off the two layers of shingles and put down a fresh new layer?

J
 
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Old 09-18-07, 10:55 AM
C
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Unless it's been damaged by water, I don't think I've ever seen the plywood replaced. I still have the original roof deck (individual boards) on my 90 year old house.
 
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Old 09-18-07, 06:15 PM
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I think that I would get a new roofer. That is a bunch of bull.
In 40 years I have never seen a complete bad deck. I have seen some bad spots which are repaired easily. I would tear off and start over. I personally would never put on shingles over old shingles. For one thing, you would not know if you have bad spots in in your deck, and secondly, the new shingles will not lay right, and the roof will get rolls in it after a year or so. Have a good day.
 
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Old 09-18-07, 08:15 PM
J
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I agree with that to. We was putting a new roof on and we decided to do the tear of and put down new felt and shingles.

Now we will have a brand new roof. I just couldnt put new ones over the old ones. Ive seen a few do it, but we decided to replace it all, except for the deck. We had a couple of spots we had to replace but they were at the top at the ridge. It was easily repaired.
 
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Old 09-19-07, 09:29 AM
K
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I'd be leery of someone automatically saying that the roof needs to be redecked during a tear-off. Get a different roofer. The decking would need to be replaced only if it is rotted or damaged from moisture.

Sometimes the need to replace is obvious. Othertimes it's a judement call. If the attic wasn't properly ventilated, the moisture could have degraded the plywood from the underside, making it soft and spongy to walk on. Plus, some older homes used 3/8" plywood, and 1/2" min may now be code.
 
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Old 09-19-07, 11:09 AM
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I've done both, reroof and total tear off. Removing old layer and refelting is a pain, but you get to check out the conditon of the decking. It usually only rots around the edges or where vents/turbines, etc. are not sealed well. One thing about reroofing--if you ever do it--make sure you tear off the overlapping shingles and put down a perimeter shingle for drip edge w/tabs facing upward & inward. This will help seal around the facia wood and you won't get rotting. Also make sure to use metal flashing around perimeter wood to keep it from rotting.
 
 

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