On Sep 25, 9:49 am, Mikepier wrote:
Last week I was asking how to cut a cast iron waste pipe in the attic
to tie in a vent. After getting a lot of advice, I think its easier
and cheaper to just cut the pipe off and continue through the roof
with PVC. Although I really did not want to go disturb the roof, I
think its a better choice.
I was told I need to put on a pipe boot. II've seen them on other
houses, but I never actually put one on. Is it straightfoward? Any
advice appreciated. Thanks

Can be done by an amateur, but it requires a bit of care. You'll need
to be lifting existing shingles (I assume you have asphalt shingles on
the roof), so if the roof is old, you will need to take extra care so
as not to break the existing shingles. If the roof is, say, 10 years
old or less, then you have a good chance of not breaking shingles.
Older than that you run an increased risk of breaking shingles. If
the roof is near the end of it's life, then it may not be possible to
do a good job of replacing a boot, but that means that you ought to be
replacing the roof anyway.

That said, here's what you will need to do:
1.) Assuming you will put the new plumbing vent in the same spot as
the old one, cut off the old cast iron pipe and pull it through the
old boot.
2.) Remove the old boot. This will entail lifting shingles to get at
the nails, and carefully pry up and remove the nails. Once all the
nails are out, then you should be able to slide the old boot out from
under the shingles. If it sticks, carefully pry it loose if is stuck
to some of the shingles.
3.) Making sure you have the right size boot for the PVC you are
using, insert the new boot in the same space as the old one. This
will be underneath the shingles above the boot, and on top of the
shingles below the boot so that water that gets in is channeled out
from under the shingles.
4.) Push the PVC up through the new boot to make sure it is in the
place it needs to be before you nail (in case it is near some
obstruction in the attic).
5.) Nail the new boot in place. You will have a couple nails on each
side throught the metal part of the boot UNDERNEATH the shingles.
Don't put any nails in the bottom edge of the boot that sticks out
from undeneath the shingles.
6.) Get some of the black roofing cement in a caulk tube, and put a
little dab of that over each nail head that is under the shingles, and
also use it to fill the old nail holes in the roof from the old boot.
Actually you'll be covering the old nail holes with the new boot, so
caulk those up before you slide the new boot into place.
7.) Go back into the attic and finish connecting up the vent
plumbing.

As I said previously, watch out for cracking or breaking off pieces of
the existing shingles. If you break one, you should probably replace
it, with means that you have to lift more shingles to remove nails,
slide out the old shingle, and then nail in a new one. Of course
doing this means that you risk breaking even more shingles, and before
you know it you are replacing the entire roof in a V pattern above
your vent hole. So in other words be extra careful about breaking
existing shingles. That is the biggest potentail problem you will
have, other than falling off the roof.

Good luck!

Ken