New installation over existing square vent

Aaron Freeman
I'm a fairly competent DIYer and have decided to tackle a re-roof of my home using metal roof over existing asphalt shingles. I understand all the basics, including the need for an appropriate barrier between the existing roof and the new roof and all the roof/ridge/rake trims, etc. The one thing that has me stumped is how to handle the exhaust vent for my oven. The original builder vented through the roof (don't ask me why -- I don't know). It's got a big (I'm guessing 8") pipe coming up into a square covered vent opening. I've found no one that offers anything to accommodate this when using metal roofing. How do you seal this up properly? (Note, moving the vent to the soffit would probably be very difficult and to the outside wall even more so (brick). I'm looking at a 26-gauge classic rub sheet roof. The roof pitch is 5/12. We don't get a lot of water here (it's rained here about 2-3 times in 2011), but when it comes it usually pours (several inches at a time). We DO get high temps (regularly 110+ in the summer) and high winds (20-30mph is normal, plus we are reasonably close to the gulf and have an occasional hurricane). Not sure if any of that's important, but figure it can't hurt for you to know all the facts. Hope y'all can help!
David Stermer
Aaron, Thanks for the question. Pipe vents are certainly a challenge, but very doable. It is beneficial if the pipe is small enough to land completely in the 'flat' of the panel. Regardless, if the pipe vent can be installed such that water is directed around the vent and not trapped, a rubber pipe boot can be used. If the pipe is too large or located such that water would be trapped, then a panel endlap at the pipe is needed. The down slope panel should be installed first, then the pipe vent and finally the upslope panel. This follows the roofing fundamental that materials are layered so that up slope material is on top of down slope material. Regards, David Stermer
Guest User
I have a similar question regarding exhaust vents and tubular skylights. I reroofed a home with standing seam paneling after tearing off the old composition roof but "saving" the built-in flashing around an existing tubular skylight. However I was unable to reposition it favorably to just the flat pan of the panel and thus had to cut a rib section out to accommodate the flashing. I did not cover the flashing (which is kind of thick) by layering it as mentioned in the comments above, but just made a round hole in the metal, carefully caulking the cracks and then caulking the outer (existing) flashing right flat to the metal pan and screwing in with neoprene washered screws. Also made sure the exposed standing ribs which were severed were filled with sealant so no water could enter that way. I did the same with a new metal bathroom exhaust vent with the metal flange, in one case caulking and screwing it flat to the metal pan without having the upper section of the panel covering the upper section of the built-in flashing. It is a fairly low pitch roof and it seemed counterproductive to have a slice in the panel above although preferred I assume. My question is, is it always forbidden to attach a metal flanged roof vent the way I described? Or should I rip it up and try to cover the upper section with a few inches of metal panel. And could one splice a section of standing seam paneling over the upper section of the vent to accomplish the same thing? I'll attach some pictures.
Guest User
I had a contractor put a new metal roof on my house in October 2016, I just realized today that they didn't install any of the pipe vents for the 2 bathrooms and the kitchen oven. Is this something that isn't needed or do I need to have this fixed? I'very tried to contact the contractor and they haven't gotten back withome me. Any help would be appreciated.
Todd Miller
Isaiah Industries, Inc.
Bj, per building code, those things need to exit the house. Having them vent into the attic or beneath the new roof will lead to condensation and eventual problems. I do feel this needs to be corrected, unless they vented then out through a wall or someplace.
Eric Novotny
An informed customer is the Best Customer!
+1 Have to be vented. Depending on the roof, should be a pretty easy fix.
Guest User
This is the response from the contractor, does this seem right? It would be a problem, if they we're steam vents, but they are plumbing vents with Oatey brand sure-vent check valve caps, nothing comes out, it just pulls air into the pipe, when needed.
Todd Miller
Isaiah Industries, Inc.
To the best of my knowledge, all relevant codes require such air admittance valves to extend through the roof. However, you can check with your local building inspector or ask the contractor to help you find wording otherwise in the building code.

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