"aemeijers" wrote in message
...
Situation- only thing left in original chimney stack is the vent for the
gas water heater. (Furnace goes out side wall just above ground level
now.) Chimney stack and flashing above roofline is failing, and may be
slightly leaking, judging by stains on bathroom ceiling right below it. I
have been quoted $800 to demo and rebuild chimney stack from roofline up,
using proper flashing instead of sheet goods and tar and gravel like
roofing company used. My father, the 83 YO house designer, suggested that
I should simply demo top part of chimney, patch roof deck and shingles,
and use a prefab metal exhaust pipe instead. How tall would it have to be?
Wind and snow load is a consideration. 5-12 roof, and current chimney is
higher than ridge line of roof. I'm concerned that a real tall metal stack
would look funny and unacceptable to any future buyers and house
inspectors.

Thoughts and ideas?

--
aem sends...


"The gas vent must be at least two feet higher than any part of the roof
within a 10 radius."

On a 5-12 pitch if the pipe exits at the mid point of the average roof on
the back side of the house I seriously doubt that it will need to be above
the ridge. The steeper the pitch the taller the pipe. 2 foot is enough on
most 5-12s. Mine is slightly taller as my pitch is greater.

All those rules being stated the closer to the ridge the more likely you can
cheat a bit if you need to and are not getting it inspected. I have seen a
lot of them draw just fine when only 1 foot above the roofline near the
ridge.

If you go this route the double wall gas vent need to go all the way down
and proper firestops need to be applied to openings created.

If you can DIY you can save a small bundle, 3" DW gas vents are not that
expensive.


--
Colbyt
Please come visit http://www.househomerepair.com