Chimney Height Question

[rijim]

Will be purchasing a Jotul F3 on Saturday to replace a stove that was here when I bought the place. I question if I can use the existing chimney which is a prefab ss that is in excellent shape but may not rise high enough above the roof. The cap is about 40" above where it penetrates the roof but it is only about 12" above the peak (about 9' away). If I understand correctly this needs to rise 2' above all surfaces within 10'; is that true? I cannot find the name of the manufacturer on the exposed section so extending is not an option; I don't want to mess with roof flashing in the cold weather, I'll wait for warm weather to replace with a new chimney if necessary.
Also the entire heigh from the top of stove to the top of the cap will be about 10'; do you think I will have draft problems?
Thank you in advance for any opinions,

Jim

 

[DAKSY]

Hey, rijim
Will be purchasing a Jotul F3 on Saturday to replace a stove that was here when I bought the place. I question if I can use the existing chimney which is a prefab ss that is in excellent shape but may not rise high enough above the roof. The cap is about 40" above where it penetrates the roof but it is only about 12" above the peak (about 9' away). If I understand correctly this needs to rise 2' above all surfaces within 10'; is that true?

Your chimney is too short...
It has to extend a MINIMUM of three feet out of the roof (on the high side) & from THERE it has to be two feet higher than anything within ten feet...
As I've said before in here, find out the pitch of you roof & multiply the top number by 10.
Add 24 to that & you will have your proper chimney height (from the higher side where the roof penetration is to the underside of the cap...)

I cannot find the name of the manufacturer on the exposed section so extending is not an option; I don't want to mess with roof flashing in the cold weather, I'll wait for warm weather to replace with a new chimney if necessary.

Can you see the Class A where it's exposed in your attic? If not, maybe you could post a couple of pix & we can ID it for you...
It DEFINITELY needs to be extended...

Also the entire heigh from the top of stove to the top of the cap will be about 10'; do you think I will have draft problems?

Your 3CB resquires a minimum of 14 feet to draft correctly...
Not exactly what you wanted to hear, but sometimes the truth hurts...

 

[rijim]

Thanks DASKY,
I cannot get to the section of the chimney that passes through the attic, it's a cathedral ceiling no crawl space. I couldn't find a min height on the jotul website but figured from other posts that I may have a problem. I will get some pictures and try to post them maybe someone will be able to identify the mfg... Looks like I won't be breaking this in this season; bummer. I need to be 6' above the roof and I'll be all set.

Thank you again,
Jim

ps: Nice bike.

 

[fossil]

...As I've said before in here, find out the pitch of you roof & multiply the top number by 10.
Add 24 to that & you will have your proper chimney height (from the higher side where the roof penetration is to the underside of the cap...)

I can't quite seem to make sense of this "thumbrule". Seems like it all depends on where the chimney penetration is through the roof. For example, if my chimney penetrates the roof very close to the ridge, such that, regardless of the pitch of the roof, if I meet the 36" minimum I exceed the 24" above anything within 10', where does the "multiply the top number (of the roof pitch) by 10" enter the equation? Rick

 

[rijim]

fossil,
You are correct in you situation, what DASKY is telling us is that if you use the rise per foot (ex. 4" / foot) and you need to clear every point within 10 feet 4" x 10' = 40" then you must be 24" above that so add the 24" which in this example would be a minimum of 64" above the high side where the chimney exits. Now if your close to the ridge measure the number of feet to the ridge and replace the 10' with that number ex if 3' to ridge on 4"/12" pitch multiply 4" x 3 = 12 " + 24" min height is 36" as you stated but move that point 4' from ridge and you will need 40" to meet the code requirements (4x4+24).

JIm