Remove and replace vent
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Photo 1: Pry up shingles
Remove one or two shingles above the vent flashing, then pry out
the vent, being careful not to damage the shingles.
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Photo 2: Nail flashing
Spread caulk under the sides (but not the bottom) of the flashing
and then nail it in place. Caulk the nail heads.
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Photo 3: Renail shingles
into place and
Plumbing vent flashings are notorious spots for
roof leaks. If you have a leak in the general area
of a plumbing vent, check the condition of the
vent flashing. Look for rust holes or gaps around metal
vents (required for cast iron waste lines). If you have
rubber vents (which are used for plastic pipe), check to
see if they have become brittle and cracked.
Both types extend under at least two courses of
shingles, so you'll usually need to remove a few shingles
above the flashing to get the old one out without
ripping any shingles. If you don't have any shingles left
from the last roofing, be extra careful not to rip any.
(Even if you can find new shingles in the same style,
the color won't match perfectly.)
Loosen the tabs on the shingles above the vent first.
Those shingles won't be removed, but you'll need to
get under those tabs to get at the nails on the shingles
directly below. Work from the top down, removing
any shingles covering the vent flashing. Getting the
tabs free without ripping them is the only tricky part.
Work a putty knife slowly under the bottom lip of
each tab and slip it through the adhesive to break the
seal from one side to the other. Don't try to pry up the
whole tab at once or it will rip. Once the tabs are free,
slip the flat bar under the shingle and tap it up under
the nail head. Pop the shingle and nail up, then pull
the flat bar out from under the shingle and pop the
nail head up from above the shingle. Don't worry if
you accidentally tear the nail head through the shingle.
When you replace the shingle, just put the nail in
slightly above the hole and fill the old hole with caulk.
Slip a flat bar under the edge of the vent flashing
and pop the nails up (Photo 1). Pull the old flashing
up over the vent pipe and scrape any old caulk and
debris off the roof. Slide the new flashing over the vent
pipe and under the shingles above the pipe. Center the
pipe in the flashing and push the flexible front corners
up or down so that the flashing pipe is parallel to the
vent pipe. (Rubber vent flashing automatically adjusts
to any pitch.) Lift the vent enough to spread caulk
under the sides (but not the bottom edge), then nail
with three 1-1/4-in. roofing nails per side (Photo 2).
Put one nail in the bottom edge with a dab of caulk
under it to seal the hole.
Set the top part of the vent on the pipe. Make sure
the inside of the lead collar fits inside the pipe, then
tighten the pipe clamp. Finally, replace the shingles