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acerunner 10-15-2010 07:09 PM

How do you flash vents on flat roof
I have several vents for a bathroom & laundry that is currently run to the side of the building and then up to the roof. This is a bit of a pet peeve because it goes through an area I'm converting to bedrooms which requires soffiting the rooms that are already really small as is.

So I am thinking about running it straight up through the roof. It is a flat roof. On a sloped roof, flashing seems pretty easy, but not sure how its done on a flat roof. Is it that much harder that the previous contractor didn't want to do?

wnabcptrNH 10-15-2010 08:15 PM

why not do a side wall vent instead of running it all the way up to the roof

acerunner 10-15-2010 08:42 PM

as I explained, the vent has to run through a couple very small rooms. Soffiting in the room will make it feel even smaller. Just exploring my options. Is it really that hard?

johnk 10-15-2010 08:45 PM

No its not hard at all for an experienced roofer.What type of roof do you have?

acerunner 10-15-2010 10:17 PM

its a tar & gravel flat roof.

johnk 10-15-2010 10:53 PM

Figure out exactlay where your hole will be,mark center by pounding a nail through from inside.Go on roof and find nail and sweep a nice area all around it,center flashing over your nail.Make a rough outline,roughly 6-8" bigger on all sides of flashing.You will need to chip rocks away from this area being careful as to not tear through layers,you only want to scrape away the top layer of asphalt that is holding the rocks.A good way to loosen the rocks is with a hammer,this will aid in scraping rocks.A paint scraper or end of hatchet should do the trick.We have a special tool,we call out here call a spud bar.Now mark out your hole,and cut out the paper with a utility knife(hole only).Center flashing on hole and nail down with roofing nails aprox 3-4 per side.Get a good fibered emulsion and spread a nice thick coat out to edge of gravel and right up and around your pipe,with a trowel.You can wait to dry and paint it or spread some gravel over the emulsion while still tacky,just make sure you have a nice thick 1/2"-3/4" and even coat before covering.I usually use mod-bit for these types of things,but this method is far more Diy friendly.

acerunner 10-18-2010 08:32 PM

thanks john

Grumpy 10-19-2010 09:36 AM

Another thing, scraping the rocks is alot easier when the roof is cool. If you're going to do this, do it first thing in the morning. After the asphalt/tar has warmed up it can become almost like trying to scrape bubble gum imbedded with rock. Not ez.

I also agree with John, mod bit is probably easier for a trained roofer but I never recommend a torch be used by a DIY'er. I personally hate tar and gravel roof repairs, unless the original roofers forgot to imbed the gravel as I sometimes see. Even as a roofer who has done numerous numerous of these repairs, I never warrant tar and gravel repairs.

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