Height of chimney

[NoSoot]

If with a wood chimney the height is typically determined from the 2/10 rule and 3 feet at a peak can you terminate less than 3 feet when you run it out a flat top chase?





Ok then,

When does a chase become a flat roof?



Just a question I wonder about.

Thanks

 

[JimWalshin845]

A few questions first for you to describe:

Size of residence and chase

What appliance(s) are you using

Is there an adjoining flue

General environment conditions

Masonry or metal

New/Old construction

Interior/Exterior design

Will it meet NFP/UL codes?

 

[webbie]

A chase is really never the roof. The manual for a particular chimney or prefab fireplace will specify the detail (how far the cap must be over) the chase....that is for fire reasons, not for draft or other codes. Hot gases coming out of the cap cannot be too close to the wood directly beneath the chase cover.

The other rules are completely separate - so unless your chase is 20 feet wide, it is not a "roof".

Also, the 2/10 and 3 ft rules apply to the metal chimney sticking out of the chase, not the actual chase

Does that answer your question?

 

[NoSoot]

If I understand this the 3 foot rule applies whenever a solid fuel chimney exits a flat roof but not a flat topped chase due to the manufactor has tested and listed their product to a reduced clearance however what defines a flat chase top verses a flat roof top? Is it size? Shape? Does the testing of the product define what a chase top is or is up to the "judgement" of the authority having jurisdiction?

I do not have a specific pending installation that this is going to relate to, I have just had this question come up before and was wondering what other people think the answer should be.

Thanks, Rick

 

[Gooserider]

IMHO a chase can be considered about the same as either a masonry chimney or a bare Class A pipe from the standpoint of the 10-3-2 rule - that specifies where the smoke has to come out. As Web mentioned, there may be fire safety related specs from the manufacturer about how far above the top of the chase you need to be with the cap.

So how does one differentiate between a flat roof and a chase? - I would say that the same standard would apply as if building a masonry chimney instead - it should be large enough to enclose the flue(s) with required clearances, but not much more. A roof would clearly cover more of the structure... I don't know if there is an official code definition of the difference, but I would think it's sort of like the definition of "obscenity" - I know it when I see it...

Gooserider