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TOPIC: Flashing

metal to metal flashing

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I have just installed a double wall metal chimney pipe through my standard metal roof. I have a galvanized square metal flashing collar to slide over the pipe. how do I flash the collar to the corrugated metal roof on the ridge side of the collar? Thanks
Guest User

12/7/2008
with a corrugated type metal roofing, you really need a special type of pipe boot to flash it. This type of boot is a silicone or EPDM rubber boot with a bendable aluminum flange around the base. This allows it to conform to the panel ribs. I have attached a picture to show what this looks like. 1. Put the panels down, cutting a hole slightly larger than the pipe 2. Cut a hole in the top of the pipe boot, slightly smaller than the pipe 3. Put a butyl sealant around the underside of the pipe boot flange. 4. Install the pipe boot, forming the flexible flange to the panel ribs. 5. Put fasteners around the pipe boot, especially beside panel ribs. 6. Put a bead of sealant around the top of the pipe boot where it meets the pipe. With some types of metal roofs you might be able to use the boot you have, but you would have to check with the manufacture of your roof to see what they say.
Nate Libbey

12/9/2008
you may want to use a pipe boot that has a heat rating. Normally orange in color. If there is a purlin system you may have difficulty screwing to a solid substrate. you may need longer screws or you may be able to use stich screws to fasten directly to the steel roof
Guest User

12/14/2008
Thanks Nate.
Todd Miller
Isaiah Industries, Inc.

12/18/2008
Will these boots work on 7/8" corrugated steel roofs?
Guest User

5/12/2010
Alfred, They should work fine with corrugated. You may have to use a few more screws to get it to conform to the ribs, but they'll work great.
Nate Libbey

5/13/2010
I have a roof with a 12/12 pitch, the boot described above won't tilt enough to touch the roof deck. I had to cut so much out, that the lip of the boot is almost even with the roof deck at the back. Should I just get a standard 8" metal bestos shingle boot and use the closure strips? Or do they make those rubber boots with the flanges for 12/12 pitch?
Guest User

12/16/2010
I'm not sure how well a shingle boot would work if your metal roofing has ribs. A way the metal roofing boot might work is if you get a smaller one. Example: If you pipe is 2", try to get the smaller pipe boots that do from a 1/4" to 2" pipe. With the larger boot, they have all that extra rubber behind them, which can create a pocket for water on a steep roof, but the small boot won't have that extra rubber around it. (this is a suggestion from a metal roofer I talked to who very recently had a similar situation come up.)
Nate Libbey

12/16/2010