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View Diary: Saturday Morning Home Repair (66 comments)

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  •  Two layers (13+ / 0-)

    will result in more heat buildup, which will cause the new roofing to deteriorate more quickly. Moisture can get in between the two layers. It's impossible to install ice shield over an existing roof. If the old surface is not level it causes problems with the new. As for warranty, most require installation over a properly prepared, level roof deck, with felt underlayment. Yes, they'll say it's an approved method, but the devil, as they say, is in the details.

    If the poster installs over the old roof, use 30 lb felt and make certain to remove and replace any broken, missing, toasted, or otherwise damaged parts of the old roof. Cut back the old around chimneys, vents, and anywhere else that flashing or other sealing is required.

    I'm not a fan, as I said, but people do it all the time. As you point out, some people do it wrong...

    "A lie is not the other side of a story; it's just a lie."

    by happy camper on Sat Jan 12, 2013 at 07:38:31 AM PST

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    •  I'll check some shingles next time Im at the store (11+ / 0-)

      You know what they say: if it doesn't say it in the guarantee, it doesn't say it. That 30 year (prorated) guarantee will still be good. or not.

      Happy just to be alive

      by exlrrp on Sat Jan 12, 2013 at 08:28:22 AM PST

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      •  Upon further review... (4+ / 0-)
        Recommended by:
        hazey, CodeTalker, boatgeek, KenBee

        Certainteed--one of the biggest roofing manufacturers--gives full instructions on their website for installing over existing shingles. The warranty does not explicitly say anything about it, but if they give you directions I'm going to assume it's covered. As long as you follow all the directions, that is. Use no felt underlayment, according to Certainteed, when installing over an existing roof...  

        Still not a fan.

        "A lie is not the other side of a story; it's just a lie."

        by happy camper on Sat Jan 12, 2013 at 11:14:29 AM PST

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        •  When we had our reroofed (3+ / 0-)
          Recommended by:
          OldJackPine, boatgeek, KenBee

          We've done both shingle and metal roofs here; shingles on the house and corrugated iron on the barn (over the partially destroyed-by-deracho roof). The barn was a DIY with friends, but the house was a $5K pro job, for which I  got a 20 year guarantee. In reading that document, the operative language seems to be "installed in accordance with" or "as part of a specified roofing system", meaning following their recommendations for prep, decking materials, nailing, compatible materials, etc.

          Ours was stripped completely; partly because of rotted decking and partly two existing layers, as well as one exposure that still had WOOD shingles for "decking" with 2 layers on top of THAT. It was a mess. But they used all new plywood, 6 feet of ice/water dam, same-brand felt and shingles, new drip edging, and even signed the paperwork, so we're fully covered. Pretty nice job, too.

          I think the operative practical takeaway is that you CAN put a 2nd layer on - and most of us would or already have done that, but none of us would ever do a 3rd. OTOH, if you have any problems under the existing layer, don't just cover it up! Strip it, because those problems WILL come back and bite you down the road. Each roof presents its' own unique challenges and problems, so as Claude always says, YMMV.

          I imagine what we have here for winter weather in CNY approximates what you get in WI, so I would first have to ask about ice build-up; not do you have any, but does it penetrate anywhere? What about wind-driven rain? Roof pitch seems to be low for snowy areas; we are mostly steeper as a rule, because of snow load. If you have never had a water penetration, maybe you don't need to worry about ice dam material; if you have had problems, don't cover this layer, fix it first.

          Common sense rules, along with some guidelines, and the actual wording on the materials paperwork or packages, IMHO. Whatever do decide, please keep us posted as you go, and we'll be happy to give you our feedback and encouragement - that's about all we can do online, without ever visiting the jobsite. Good luck.
          John

          "...greed and selfishness and striving for undue riches can never bring lasting happiness or good to the individual or to his neighbors." FDR

          by CodeTalker on Sat Jan 12, 2013 at 12:40:10 PM PST

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