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OwenChristensen
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# Posted: 24 Sep 2012 08:06am
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I've built several buildings with metal roofs , but I've never put a chimney flashing in one. I need to do next week. I'm guessing I'd better wait and put the chimney right on a single steel run. I can't figure how to do it if it's part way between sheets.
Owen
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Martian
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# Posted: 24 Sep 2012 08:39am
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Owen, the way we do it is to split a sheet, cut around the flashing allowing for a 4" underlap on the bottom panel, and use butyl rubber (gutter caulk) to seal the lap and the flashing. If the chimney happens to fall at a seam, you will need to split and cutout both sheets. We order panels 6" longer to fit around chimneys and other projections. Ideally, the chimney will exit the roof such that the flashing can go under the ridge cap. If the job can afford it, you can get hightemp, flexible boots that get screwed down around the chimney.
Tom
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MtnDon
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# Posted: 24 Sep 2012 10:11am - Edited by: MtnDon
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I've used these silicone rubber boots for chimneys and other pipes that penetrate metal roofs. I cut the hole through the sheathing first and then lay the metal and screw it down. Then either cut the metal from below or drill a few perimeter holes through the metal from below and then cut from the top. Recipro saw or jigsaw with metal blade.
Then for the flashing use a silicone boot. They have a "dead soft" aluminum ring molded into the boot. It conforms easily to the rins. Shape it and then use some metal roof approved caulk under the boot and screw down. Mine have never leaked. Just take time to shape the boot seal.
I get mine from a local metal roofing materials dealer. The one pictured shows it between ribs but I've had them centered on the joint rib of two panels,
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OwenChristensen
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# Posted: 24 Sep 2012 06:15pm
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Thanks I think I get it. I might have to ask some more questions later.
Owen
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Malamute
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# Posted: 24 Sep 2012 10:44pm - Edited by: Malamute
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It's been described well so far. If you need to transfer the centerline of the stove pipe from below so it goes between the rafters, a 22 rifle works well. You can then go up on the roof and make the cut out easier.
With the quality boots, it doesnt matter much where it ends up in relation to the ribs or valleys, there are other considerations, like where you want the stove, and where the rafters/trusses are, and your clearance from them.
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MtnDon
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# Posted: 24 Sep 2012 11:49pm
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Quoting: Malamute where the rafters/trusses are, and your clearance from them.
Yep. That is the most important part. Everything else is fitted from there.
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toyota_mdt_tech
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# Posted: 25 Sep 2012 11:45pm
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Quoting: MtnDon I've used these silicone rubber boots for chimneys and other pipes that penetrate metal roofs. I cut the hole through the sheathing first and then lay the metal and screw it down. Then either cut the metal from below or drill a few perimeter holes through the metal from below and then cut from the top. Recipro saw or jigsaw with metal blade. Then for the flashing use a silicone boot. They have a "dead soft" aluminum ring molded into the boot. It conforms easily to the rins. Shape it and then use some metal roof approved caulk under the boot and screw down. Mine have never leaked. Just take time to shape the boot seal. I get mine from a local metal roofing materials dealer. The one pictured shows it between ribs but I've had them centered on the joint rib of two panels,
I had mine professionally installed and that is how they did it. Just cut the pipe hole, slide the pipe through, slide the flashing over the pipe, formed it to match the metal roof, its sealed all around the edges and screwed in. There is another flashing on the pipe to shed water over the joint where the roof flashing meets the pipe.
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OwenChristensen
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# Posted: 26 Sep 2012 07:52am - Edited by: OwenChristensen
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a 22 rifle works well. LOL! Becareful I got chewed out for shooting a shotgun in the air. I only shoot grouse on the ground now.
I've put a lot of chimneys in, I just wondered about the metal roof.
As far as locating the chimney, I figure the location of the exit on the stove and draw it onto the floor, then use a plumb bob to find the center in the cieling joists and on up to the roof sheathing, then screw a screw thru. A sort string and plumb bob from the top opening of the flashing, can get the flashing exactly in the right spot. I trace the whole inside bottom edge of the flashing and cut the hole. If the chimney needs to be on a rafter location, just cut the rafter and frame a solid box, just like you would for a stairway in a floor.
I guess I never have noticed those boots.
Owen
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