Wood stove flue installation

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chhamilton

New Member
Jul 22, 2021
11
Montreal, Quebec
I'm in the middle of a new home construction where we're installing a wood stove in front of a large window which extends to the ceiling. Ideally we'd like the flue to pass through the ceiling, at an angle through the attic, out the wall below the roof-line, and then extend vertically from there. All of this so that we can avoid having an unsightly chimney box on the roof very close to the roof edge. The roof is a flat roof that slopes inwards towards a central drain. The attic has about 3' of loose cellulose insulation, and the flue comes up between two roof trusses that are spaced 24" o/c, so we have lot of roof for constructing a box and any necessary heat shields, etc.

I've approached 3 installers and they all have stated they want to go straight up through the ceiling and through the roof. Nobody has been able to explain to me why we can't go through the wall instead. Does anybody here know what the building code has to say about this? I've attached an image of the desired installation. Note that I'm in Quebec, where things might be different than elsewhere.

DesiredFlue.png
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
25,608
central pa
I'm in the middle of a new home construction where we're installing a wood stove in front of a large window which extends to the ceiling. Ideally we'd like the flue to pass through the ceiling, at an angle through the attic, out the wall below the roof-line, and then extend vertically from there. All of this so that we can avoid having an unsightly chimney box on the roof very close to the roof edge. The roof is a flat roof that slopes inwards towards a central drain. The attic has about 3' of loose cellulose insulation, and the flue comes up between two roof trusses that are spaced 24" o/c, so we have lot of roof for constructing a box and any necessary heat shields, etc.

I've approached 3 installers and they all have stated they want to go straight up through the ceiling and through the roof. Nobody has been able to explain to me why we can't go through the wall instead. Does anybody here know what the building code has to say about this? I've attached an image of the desired installation. Note that I'm in Quebec, where things might be different than elsewhere.

View attachment 280406
I would only do it straight up as well
 

brenndatomu

Minister of Fire
Aug 21, 2013
6,415
NE Ohio
I'd think that going out through the wall at an angle would be exceedingly hard to waterproof safely and reliably.
 
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chhamilton

New Member
Jul 22, 2021
11
Montreal, Quebec
I would only do it straight up as well

Can you share the reasoning why? Is it a code thing, or more an issue of simplicity of maintenance and performance long term?

It seems very common to go near horizontally through exterior walls and then vertically up the side of the house and I'm just curious what the difference is with a setup like I'm proposing.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
25,608
central pa
Can you share the reasoning why? Is it a code thing, or more an issue of simplicity of maintenance and performance long term?

It seems very common to go near horizontally through exterior walls and then vertically up the side of the house and I'm just curious what the difference is with a setup like I'm proposing.
They are next to impossible to keep weather tight. It will cost atleast twice as much and not work as well. If someone did convince me to put one in like that for them I would tell them when it leaks it isn't my problem
 

chhamilton

New Member
Jul 22, 2021
11
Montreal, Quebec
They are next to impossible to keep weather tight. It will cost atleast twice as much and not work as well. If someone did convince me to put one in like that for them I would tell them when it leaks it isn't my problem

Is it as big an issue for a near horizontal run through a wall (which seem very common) as it is for a run on an angle?
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
25,608
central pa
Is it as big an issue for a near horizontal run through a wall (which seem very common) as it is for a run on an angle?
No horizontal is not a problem at all
 

chhamilton

New Member
Jul 22, 2021
11
Montreal, Quebec
No horizontal is not a problem at all

I guess I should have been more clear in my original post. I do t care if the run through the attic is near horizontal or on an angle. I just would really like (esthetically) for the chimney to come out the side of the building below the roofline, rather than having a box on the roof right near the roof edge.

And I'm trying to understand if installers are refusing because (a) it's not allowed per code or (b) it's a bad idea for maintenance/performance reasons or (c) it should be fine but they just don't do it often.
 

bholler

Chimney sweep
Staff member
Jan 14, 2014
25,608
central pa
I guess I should have been more clear in my original post. I do t care if the run through the attic is near horizontal or on an angle. I just would really like (esthetically) for the chimney to come out the side of the building below the roofline, rather than having a box on the roof right near the roof edge.

And I'm trying to understand if installers are refusing because (a) it's not allowed per code or (b) it's a bad idea for maintenance/performance reasons or (c) it should be fine but they just don't do it often.
You could by code run with 30 degree angles like you have shown. You wouldn't be allowed to run up and then 90 out above the ceiling by code.
 

gthomas785

Minister of Fire
Feb 8, 2020
502
Central MA
Hmm, I'm curious. Usually, people consider a through-the wall installation to be more unsightly than through the roof. Can you share some pictures of the outside (or drawings, if the building's not there yet) so we get a better idea of what you're dealing with?
You don't need to have a "chimney box" visible from the outside, it would just be a pipe sticking up through the roof with flashing around it. I assume this is a rubber roof?

One thought that comes to mind if you want to avoid having the chimney at the edge of the roof would be to jog the pipe at 30 degrees the other way, toward the interior of the house, then up from there. That way the roof penetration will be less visible from the ground.
 

chhamilton

New Member
Jul 22, 2021
11
Montreal, Quebec
Hmm, I'm curious. Usually, people consider a through-the wall installation to be more unsightly than through the roof. Can you share some pictures of the outside (or drawings, if the building's not there yet) so we get a better idea of what you're dealing with?
You don't need to have a "chimney box" visible from the outside, it would just be a pipe sticking up through the roof with flashing around it. I assume this is a rubber roof?

The building is basically a rectangle, with a flat roof and no roof overhang to speak of. So having a "box" on the top of the roof quite close to the roof edge ruins the visual a bit. The installers strongly recommended having a box that sticks out 18" to 24" to receive the chimney flashing, and which is itself covered in the roofing material. The roof is not EPDM or TPO rubber, but rather its asphalt roll roofing.

I don't mind the look of a horizontal through-the-wall installation, because you really mostly see chimney. But I'll admit I'm not a huge fan of the 30 degree through the wall look.

One thought that comes to mind if you want to avoid having the chimney at the edge of the roof would be to jog the pipe at 30 degrees the other way, toward the interior of the house, then up from there. That way the roof penetration will be less visible from the ground.

Ah, that's an interesting idea I hadn't considered. We've got about 5' of attic space, which would give something like 20" more displacement from the edge.