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I have a job to put a metal chimney through a metal roof and flash it tightly against Maine weather. The roofing is the typical painted, ribbed steel roofing. I can build a “faux” chimney and cover it with clapboards to match the siding, or flash the chimney directly. I’m not entirely sure how to flash either.
In looking at pictures in FH, I’ve seen a couple that appear to be flashed directly (no “faux”).
I’d like to hear suggestions about how this can be (or, even better, is) done.
Thanks ..
JG
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Hello John,
I just did a job exactly like yours: 6" solid insulated chimney (8.5" o.d.) through 3/4" raised rib panel on a 7/12 pitch. Our local metal supplier did not carry anything to flash a chimney. You can buy a special pipe flashing for metal roofs. It is a neoprene rubber boot with a deformable aluminum ring. They come in sizes for up to 13" pipe. However, I opted not to use this since 1) it does not allow for ventilation of the chimney and 2) the rubber may not stand up to the outside chimney temperatures if a chimney fire occured (+500degF). Instead I used the standard galvalume cone flashing supplied by chimney distributors. I made a form using a piece of roofing and a wood block and deformed the flange of the flashing to conform closely to the ribs. Then butyl rubber tape and silicone caulk and neoprene washer screws every 2-3" around the perimeter of the flashing (need solid 2x backing under perimiter of flashing). Later on I may box the chimney in and use standard L flashing, but this worked out pretty well and doesn't look all that bad. And No leaks.
Hope this helps.
Steve
*John: Dektite makes two flashing like steve described above. One for standard applications & one for high temperature. They work very well. We buy ours from Dynamic Fastener in Kansas City.1 800 821 5448. Try one & you will use them again.Ron.
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John,
I'm a metal roofing contractor. We usually make a flashing in our shop for this. It has a flat base with oblong hole cut in it and then a round section soldered to it. The round section fits loose around the pipe, with about 1" clearence.
The joint between the pipe is covered with a storm collar that is field cut.
You might call a local sheet metal shop to get one made for you.
The roof panel goes on top of the flashing and is cut about 3" away from the pipe. The openings at the panel ribs are capped with field made closures and sealed with tape mastic and screws.
JohnKirk
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John
I strongly recommend that you build the
i faux
chimney, and not rely on tape or caulk. The metal roof manufacturers all make 'side wall' and 'end wall' flashings that can be used to properly flash a square(faux) chimney chase . I've done several and have never had a call back, 10 years and counting. I've also had to attempt to repair badly done 'non-faux' installations that will likely leak forever. . . too many places to breakdown, too much reliance on caulk, and good luck!!!
While I do use silicone caulk as an added precaution, careful overlapping of the various flashings and the roof pans make it redundant. I close off the top of this square chimney chase with a 'flat roof' cone flashing, with edges bent down over the walls of the chase and collar, retaining all recommended clearances (2"+) between the
i chase
and the chimney.
-pm
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I have a job to put a metal chimney through a metal roof and flash it tightly against Maine weather. The roofing is the typical painted, ribbed steel roofing. I can build a "faux" chimney and cover it with clapboards to match the siding, or flash the chimney directly. I'm not entirely sure how to flash either.
In looking at pictures in FH, I've seen a couple that appear to be flashed directly (no "faux").
I'd like to hear suggestions about how this can be (or, even better, is) done.
Thanks ..
JG