03:25PM | 05/03/03
Member Since: 05/02/03
2 lifetime posts
I am installing a galvanized steel roof over existing asphalt shingles which will first be strapped with 1X4's. What is the proper way to install attic vents so they don't leak, etc. What are the best vents to use? There are no pre-existing vents on this 1940's home (yikes!). My house is 1000 sf with a pyramid style roof.

Brian Wood

11:58PM | 05/04/03
Cody, first take off the shingles. The intense heat under the metal will dry & crack them, they will come loose and you'll have an unstable roof.

To avoid leaking vents, just install a full-length ridge vent, or as much as you can. Zero leaks.

Another tip to help lower your cooling bills, coat the metal white with a good quality elastomeric product. & come to mind.

Good luck with your new roof.



05:52AM | 05/06/03
Member Since: 05/02/03
2 lifetime posts
Hi Brian. Thx for your advice. Our roof is an unconventional pyramid design, meaning we will have at least 4 ridge caps that all meet in the centre of the roof. Would you still recommend ridge cap vents and if so, would you vent all four? Also, we've gotten lots of yeas and nays regarding removing the shingles first. We were left to understand as long as the roof was strapped that the heat problem would take care of itself. Thx again. Cody

Todd Miller

05:14PM | 05/14/03
Member Since: 11/13/99
7 lifetime posts
I have worked with residential metal roofing on thousands of installations since 1981. Probably 80% of those jobs have been over existing shingles. Never, not even once, have I encountered a job where going over the old shingles made the roof unstable.

Next, most types of metal roofing are designed for installation over solid decking or existing shingles (with new underlayment). If you install strapping first, make sure that the roof panels you're installing are appropriate for that type of application. Don't mess around -- contact the roofing manufacturer and inquire with them.

Next, with a pyramid style roof, you will need to use standard square static vents. Again, inquire with your roofing manufacturer for proper flashing methods.

The vents you're installing are there to allow unwanted heat and excessive moisture out of the attic. Your metal roof is not "putting" these things in there though. The need for ventilation is the same no mater what type of roof you're installing. As we do things to make homes tighter, we must increase ventilation.

Finally, these vents are for "exhaust" ... to function properly, you also need "intake" -- normally soffit vents.

Contact me if you have further questions.


12:42PM | 07/05/15
can I achieve proper roof venting on my cathedral hip roof by insulating with batts (no more vents) , using a breathable roofing membrane and double strapping the steel roof with a continuous as possible ridge vent?
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