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new roof vs going over existing roof

I'm looking to put a new roof on my house. my existing shingle roof is approx 21 yrs old. I live in Md. I remember in the old days roofers would put a new roof over the existing shingle roof. It seems now the roofing companies are tearing off the old shingles then putting on new roofs. I would think that 2 layers of shingles would give you better protection as long as the existing roof is in good condition Any thoughts on New vs going over the existing roof

Re: new roof vs going over existing roof

Your local code may allow multiple roofs (2 or even 3 in some places), but roofers rather tear the old roof(s) off because it allows them to see what's under the roof, make corrections, replace damaged lumber, check for water damages, dry rot, split and broken members, replace the felt paper, etc. If they are going to stand behind their work, they want to make sure it's done right through out.

If you look at your roof and it looks fine, you still can't really see what's under it. You can't determine the condition of the tar paper under the shingles (or tiles), which is so important in keeping water away.

The difference in labor in removing everything down to the deck, is worth it in the long run.

Last thing: Insist on roofing nails, nailed according to mfg's guidelines, to fasten the new shingles, if that's what you will be putting on. If your roofer wants to use staples, just say NO.

A. Spruce
Re: new roof vs going over existing roof

Ditto everything DJ1 just said. In addition, overlays do not last as long and do not look as good as single layer roofs. Make sure that all your roof metals, including gutters get changed out. While they may be fine now, you don't want them rusting through in a few years, which will require disturbing the roof to replace them, creating the potential for leaks.

Re: new roof vs going over existing roof

Besides checking the deck and flashing, ice & water shield (self adhered membrane) can be put down in the appropriate locations. Not commonly used 20 years ago.

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