the Shop under a New Roof

digitFebruary 11, 2009

Can old rolled asphalt roofing be trapped under a new roof without harm?

My backyard shop is a gable roof building that was once a small garage. When it was converted to a shop, a carport was built on to one side.

Probably 15 years ago, both the shop and carport were covered with roll roofing. Since it starts at the shop eves, the angle of the carport roof is very shallow. Carrying quite a bit of snow the last 2 Winters, the carport roof begun leaking. The roof deck and even the rafters are in bad shape now.

I guess the carport roof is over 40 years old  it should be entirely removed. If a new carport roof starts at the peak of the shop, the angle would be much steeper and better for shedding water.

Starting at the peak of the shop would trap that slope of the shop roof beneath this new roof. I will use metal roofing over the entire structure  both shop and carport. Is there a problem with leaving the existing asphalt roofing on the shop and simply covering it with the metal roofing?

I donÂt know if it makes any difference but keep in mind that the new roof would sit directly on one slope of the shop and be elevated above the other slope. To keep the birds out of there  IÂd enclose that area with OSB board.



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no problem just covering it over. around here they lay 1x4 across teh roof spaced 3-4' apart vertically, but continuous horizontally. then the metal roofing is secured to the 1x4s. the old asphalt is left in place.

    Bookmark   February 12, 2009 at 12:31PM
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Well, that will sure make the job an easier one. Not only won't I have to rip the asphalt roofing off, I won't have to haul it away.

This is an arid part of the US but I still had a little concern about moisture. I can't see how it would be any greater than just the asphalt on the wood without the metal roofing above it.

Thank you!


    Bookmark   February 13, 2009 at 1:38AM
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