i have alot… maybe 40 roof penatrations and climbing on my flat roof (not dead flat 24″ fall in 75 ft) built up roof 5 ply over 3-4″ foamboard… so many vents because inside is exposed roof structure…..
what i usually do…
use all metal (galv) vent/pipe flashing… with a small torch i reheat the roof surface area where the flashing flange will rest and an extra 3″ all around, then push the flashing down the pipe and let it bed itself into the hot tar… I then have precut pieces of torchdown that are about 2.5 -3″ bigger than the galv flashing with a hole in the center… i heat/melt the back of these and drop them over the flashing where they cap the galvanized flat part and fuse to the built up… i try to get a small amount of “squeeze out” around the outer edges and around the inner hole edges of the torchdown… i have been known to come back and poly roof caulk the edges..
is this overkill? cold i use just the poly roof caulk under the flashing and skip the torch and torch down?
what is industry standard…? i just developed this process for roof moisture vents years ago and have kept doing it…. in fact i use to bed in /melt in a piece of torch down before/under the flashing flange first (same size as flange) then the flashing then another piece of torch down over that…
this is another situation where I’ve always done my own builtup roofs because i had the equipment and access to information but zero experience (until the first day)
thanks in advance
p
Replies
Sounds good to me.
For a five ply roof, standard is to seat the flashing the way you describe in hopt stuff, then hot mop capsheets over it three ply with each slightly larger than the previous
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thanks...
my method was kinda just... "i think this will do" but i didn't know if it was overkill
hate have'n to fire up the kettle... why i turn to torchdown so often...
the pipe/vent flashing i have is so tight on 2" pcv there is no come'n back once you push it down the pipe....
just for the record... i use poly caulk around the roof penatration (we use the correct size hole saw) and i sometimes leave them for months and have never had a leak with just the caulk so there is always a second line of defense under the flashing...
thanks again
p
Lead flashing for plumbing pipes still the norm for flat roofs out here in the great north wet.
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