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We are wanting to put a metal roof over our existing asphalt shingle roof. One outstanding question is the best way to seal the various vents that poke through the roof. Is silicon caulk the preferred sealant?
Also, we are wondering if it would be better to pull the asphalt shingles off, put new 30# felt down, and then put the metal roof on top of that, rather than over the old asphalt shingles. Seems like that over asphalt there could be problems of bending the metal when walking on it.
Thanks,
Rod
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For pipe penetrations, there are a variety of flashings available which can be used with most stles of metal roofing. These flashings typically have a rubber boot which seals around the pipe and then a metal frame of some sort which is flashed into the roofing.
It is also possible to custom make pipe flashings from metal which matches the roof.
It is always best to follow the manufacturer's instructions as to handle penetrations and other flashings.
As for attic vents, most styles of those can also be used. Again, the exact installation method depends upon the profile of roofing you choose. Make sure you have full instructions from the roofing manufacturer as well as available phone support before emnarking on this, or use a qualified and experienced professional installer.
Many metal roofs are designed for going over existing shingles. This is due to the low weight of metal roofing and also due to the design of the products. Some styles of metal roofing can also be installed on top of lathe which would be installed over the old shingles.
Again, different metal roof profiles have different requirements.
Once you choose the metal roof you're going to install, verify proper installation methods with the manufacturer of the roofing.
Good luck. Contact us if additional questions come up.
5/4/2003
Isaiah Industries, Inc.
5/4/2003