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Curbing to raise exhaust vent

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Guest User
8/3/2009
I've read all through your flashing questions and I have a new one. First of all, I have to extend my bathroom vents through my roof. I'm using an imperial rib galvalume product. The roof cap for the vent is square and will only project about 2 and a half inches above the deck. I'm concerned that it will get buried by the snow, so I wonder if you think I should mount it up on a curb? My roof pitch is 4/12 and I plan on using snow guards to keep snow from dropping 2 stories onto my deck. If I raise this by about 3", how would I flash the square curb? I would install this vent centered over a lap joint in the panels. What do you think about me using some rubber roofing material to make flashing?
Ken Buchinger
NCI Building Systems, Inc.
8/3/2009
I would use a rubber roof jack, which is typically sold my most all metal roofing suppliers. Use tape sealant between the roof jack and the metal roof and fasten it to the roof with the appropriate long life fasteners at about 1" on center. At the top, use urethane sealant between the roof jack and the pipe and install a stainless steel microgear clamp over the top band of the roof jack. I would also install a snow guard up slope from the pipe to prevent sliding snow from shearing it off.
Guest User
8/3/2009
Do they make a boot jack for square bases? This isn't a pipe. It's a vent cap that will be elevated off the roof on a curb about 3". We often get a lot of snow here so I need to raise it up so it won't get buried. The base measures 9 1/4" x 11" I'm pretty sure there won't be a problem with shearing off because it will be securely fastened to a broad base, but I will have a snow guard just up slope from it anyway. By the way, I am using a roof jack for my stink pipe.
Ken Buchinger
NCI Building Systems, Inc.
8/5/2009
There are some square rubber roof jacks available, though in limited sizes. I have been successful in the past using a round rubber roof jack over a square tube and getting it well sealed with urethane and a stainless clamp as previously described. One application I remember was in Chicago on a commercial roof with a weathertightness warranty which has performed flawlessly for several years now.
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