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TOPIC: Roofing over existing roof

New roof on old construction

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I have a problem with which way to go for a new roof. I have read dozens of posts here but have yet to find the exact answer to my question and concerns. I have received ‘alot’ of suggestions from contractors and no two give the same advise. I will be doing this myself. The house was built in the 1850s with subsequent additions around 60 years ago. Overall it has been well maintained and is structurally sound with straight roof lines though there are some areas of the eves that need attention (it has aluminum for siding and trim). It currently has a raised seam steel roof that has started to root (rust) on the edges as well as a few minor leaks during heavy rain and must be replaced. The raised seam is installed over cedar shakes which are directly on planks (no sheathing) and the planks, being old have sizable gaps from 1/8 to 1/2 in. I have been told (also told by a contractor this is how to do it economically) that I can simply hammer down the seams strap it and install the new roof. I do not like this idea but am on a limited budget and must roof the house. I would prefer to remove both the existing roof and cedar but have two concerns; first and foremost is what I might find in regards to integrity (out of sight out of mind though I know this is not really the way to look at it); second is the cost of sheathing if it must be installed between the planking and metal roof. If a structural metal roof is used can it be installed directly over the original planking (provided it is sound) with a simple layer of 30lb between the two? I do know different manufactures have different recommendations and final manufacturer decision will be based on how the project is undertaken. One suggestion was to remove the existing metal roof and install directly over the cedar shakes, I do not see this as a smart or safe option though. Another contractor suggested simply cut away 2ft from the edge and install a new flat edge and recoat with Karnack roof finish. Are there other options that may be considered? The bottom line is that this is going to be a DIY and must be done at the lowest possible cost but with correct installation and longevity in mind. Any suggestions would be welcomed.
Bob Baldwin

6/21/2008
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Because of potential problems with expansion and contraction rates, I generally do not like putting new metal roofing over old. If you choose a metal roof that goes over battens though and you flatten down the current ribs and put down battens before the new metal you can probably make this a successful installation. Todd Miller
Todd Miller
Isaiah Industries, Inc.

6/22/2008
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If we decide to remove the old can a new metal roof effectivly be placed over the planking with only 30lb between them or is sheathing needed? Thanks in advance
Guest User

6/22/2008
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It depends upon the product you choose. Virtually all products can be installed over solid decking but many can be installed over space boards as well. Todd Miller
Todd Miller
Isaiah Industries, Inc.

6/22/2008
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