code question on height above roof deck for water heater vent


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...

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

"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
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

The 10 foot radius rule - does that mean 10 feet as measured along the roof, or 10 feet horizontal distance? On a 5-12 pitch roof, if you go out from the chimney emergence point 10 feet horizontally, the roofline is then at (10/12) X 5 feet, or 50 inches, plus 24 means your chimney must stick up 74 inches above the point where it emerges from the roof. If the rule means 10 feet measured along the roof, that would be (10/13) X 5 feet, or 46 inches, so the chimney would only have to stick up 70 inches overall. Not a big difference, but could be if the inspector is a stickler. Not sure where you get "2 foot is enough on most 5-12s." --H
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

The 10 foot radius rule - does that mean 10 feet as measured along the roof, or 10 feet horizontal distance? On a 5-12 pitch roof, if you go out from the chimney emergence point 10 feet horizontally, the roofline is then at (10/12) X 5 feet, or 50 inches, plus 24 means your chimney must stick up 74 inches above the point where it emerges from the roof. If the rule means 10 feet measured along the roof, that would be (10/13) X 5 feet, or 46 inches, so the chimney would only have to stick up 70 inches overall. Not a big difference, but could be if the inspector is a stickler. Not sure where you get "2 foot is enough on most 5-12s." --H -----------------------------------------------------
I quoted from a water heater installation manual I had in the filing cabinet. That is also the rule as I recall it from memory.
To the best of my knowledge It is 10 foot of run parallel to the ground.
5/12 pitch is not common on larger homes in my area. They are very seldom used where the midpoint of a gable roof would have more than 7-8 feet of run to the ridge. The average being about 6 foot. That would be 30" of rise above the roof at the roof plus the 24" if you want to be a stickler for the rules
Persons installing a gas vent should follow local codes. Only a fool would install one without determining what the local inspector wants if they plan to have it inspected. The codes may different here but vents seldom go more than 3 foot above the roof and are quite often less. I just went out and looked at all 3 of mine which were inspected and approved in 1995. Not a one of them meets the rule I posted.
The last time I received a notice to correct one for a rental property, all that was mentioned was get it above the roof line.
All that really matters is that the silly thing draws properly when tested.
Colbyt
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

You probably have to maintain the height to be in compliance. I forget the exact working, but it must be x higher than anything within 10 feet. I'd consider removing the chimney completely and getting a new high efficiency water heater with an outside vent rather than a chimney. Total cost may be similar and no headaches later.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Ed Pawlowski wrote:

I hadn't even thought of that. Recovering that corner would be nice for the eventual (probably by next owner) bathroom gut job and remodel.
Too many options- brain freeze coming on.
I just dabbed a coat of Killz over the stains in bathroom ceiling. If the stains don't come back right after the next rainstorm, maybe I'll procrastinate the repair another year, or leave it for the next owner.
--
aem sends...

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

A can of roofing cement should be less than $20. Why not spend the 1 hour time to do a patch rather than paint and then have to patch anyway. You can always build a frame around the existing chimney and cover it with wood/vinyl to math your existing siding and prevent further weathering, and put a new cap on the top to cover the wood/ vinyl. Check your local code enforcement folks for the 10 foot radius to the highest point, etc, requirments to be sure it is your local requirment.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.