Lets talk chimney height

[John Dirks Jr]

As far as chimneys go, when do you call them out for being too low? Do you have different standards for wood burning vs gas flue chimney?

What I mean by that is a chimney that is used exclusivly for venting a gas flue and is not used for a fireplace compared to one that is used for venting a wood burning fireplace.

The reason I ask is after being taught what the standards were in my class and looking around at chimneys on the houses in my area, the majority of them are too low.

Am I missing something here?

[Ed Ochs]

See IRC R1003.9 Termination...

Shall extend at least 2' higher than any portion of the building within 10' and also will be not less than 3' above the highest point that it passes through the roof

[drw]

Originally posted by AHI

As far as chimneys go, when do you call them out for being too low? Do you have different standards for wood burning vs gas flue chimney?

What I mean by that is a chimney that is used exclusivly for venting a gas flue and is not used for a fireplace compared to one that is used for venting a wood burning fireplace.

The reason I ask is after being taught what the standards were in my class and looking around at chimneys on the houses in my area, the majority of them are too low.

Am I missing something here?

Are you referring to masonry chimneys, or metal heating/water heating vents? B-vents can terminate as low as 1 foot above the roof.

[jon_ran]

You have to remember that a gas vent is NOT a chimney.

[John Dirks Jr]

Originally posted by drw

Originally posted by AHI

As far as chimneys go, when do you call them out for being too low? Do you have different standards for wood burning vs gas flue chimney?

What I mean by that is a chimney that is used exclusivly for venting a gas flue and is not used for a fireplace compared to one that is used for venting a wood burning fireplace.

The reason I ask is after being taught what the standards were in my class and looking around at chimneys on the houses in my area, the majority of them are too low.

Am I missing something here?

Are you referring to masonry chimneys, or metal heating/water heating vents? B-vents can terminate as low as 1 foot above the roof.

For the sake of clarification on the whole issue I am refering to both. Keep in mind that masonry chimneys are many times used exclusivly for venting gas furnaces.

So what you are saying is that if the masonry chimney serves only a gas appliance it only needs to be 1 foot above roof the line?

I was hoping someone would chime in and give a # of different situations and their height requirements

[drw]

Originally posted by AHI

So what you are saying is that if the masonry chimney serves only a gas appliance it only needs to be 1 foot above roof the line?

No. I am saying that a metal B-vent (double walled) can be AS LOW AS 1 foot. Even this will vary depending on the slope of the roof it is penetrating (the steeper the slope, the higher the termination point). My understanding is that for masonry chimneys, regardless of function, the 3-2-10 rule applies...the chimney must terminate at least 3 feet above the roof, and 2 feet higher than any part of the structure within 10 feet of it.

[chicago]

John does make an interesting point though.

For practicle purposes why would it have a different height rule ?

[Brandon Whitmore]

I may be the only one out there, but I never call out the 3-2-10 rule on a chimney used as a chase for a B vent to run through for a furnace. Now if someone ended up connecting a wood stove or something , that would be a different issue, but then permits should be pulled and that should be caught--- right?

Is a masonry chimney really considered a chimney per the requirements if it is not in use(besides being a chase)??

[chicago]

Looks like a loop hole.

[JerryM]

Chimneys & Vents: IRC, Chapter 18.

Chimneys & Vents: UMC, Chapter 8

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