10/2 rule for chimney

[jzinckgra]

We're looking to put a stove into our new house and have a 12/12 pitch roof. We wanted to do corner install, but stove shop says they'd have to have 13' of exposed pipe on the outside, which not only would be very expensive for SS, would look bad. Our builder is going to build a chase, but even that would look bad and would probably need some support. Anyways, are other option is to put the stove into the middle of the room and exit the pipe at the cathedral ceiling. We'd need 24' od double wall before roof penetration. After taking into account the size of the stove (T6) and the hearthpad, this option takes up a lot of floorspace vs the corner option.

So, is the 10/2 rule for the chimney due to the potential for fire from embers hitting the roof or is it due to drafting of the stove? if it's the former, I don't understand as if you exit at the peak, you only have to be 3' above the roofline, which puts the chimney a lot closer to the roof (and potential for fire) then the corner install which says you have to be at least 10' away from the roof, then 2' above that point. I don't understand

 

[DAKSY]

The Chimney 2-3-10 Rule is the guideline for determining proper chimney height.
Improper or inadequate draw of the combustion exhaust gas can cause major safety problems for the home's occupants. Smoke and other exhaust gasses from the combustion of wood or fossil fuels contain carbon monoxide, carcinogens, and other harmful chemicals. The flue’s job is to carry these poisonous gasses out of the house. If the chimney is not tall enough, the flue can’t do its job, exhaust gasses are released into the house, and a hazardous condition is created.
Structures that are too close to the opening of the chimney flue can directly affect the way the flue “draws”, or exhausts the gases produced from combustion in the fireplace, stove, or other appliances. The solution to the problem? Extend the chimney to provide a minimum of 2 feet clearance to all roof surfaces and structures within 10 feet of the chimney and 3 feet above the highest point that the chimney penetrates the roof (i.e. the side of the chimney furthest up the roof slope). This is a national code, outlined in section FG503.5.4 of the International Fuel Gas Code.

 

[xman23]

Mine is in the cornor with a single wall straight up to the ceiling box. From the box up is double wall up thru the 12 /12 pitch roof. On this side of the house there is 5 /12 pitch side porch roof that intersects the main roof above where the chimney comes out. Yes the chimney is high above the roof, with 2 brace rods to support it. It's at the back of my cabin in the woods. It looks fine to me.

If you move to the center of the house you can use single wall inside and a small amount of double wall thru the roof and above. Consider how you will clean the chimney. I do mine from the top down from the shed roof. How ever you do it figure lay the location so you can box out the chase thru the roof. If you need some pictures let me know I'm sure I can find some.

Tom

 

[firefighterjake]

I have a stainless steel chimney that runs up a long ways . . . I won't address the extra expense . . . but I can address the looks. I originally figured I would build a wooden chase around it since I wasn't keen on having such a long run of shiny metal on the outside of my house . . . but I thought I would do it in Year 2.

What I discovered during the first course of the year though was a) I grew accustomed to the look on the side of the house, b) it was very convenient to have the outside chimney with a T at the base as inspecting and cleaning the chimney is a 10-minute job and c) due to the placement of the stove and house I discovered that any folks passing by walking or in their cars can pretty much only see the very top 3 feet or so of the chimney . . . and so I left it as is . . . obviously this worked for me with the location of the stove and house and my own aesthetic tastes . . . your situation could be quite different.

 

[jharkin]

Another consideration - if you are intending to heat the entire house, having the stove in a more central location might help with more even heat distribution.

 

[RichVT]

We had the same problem locating a stove in our house. We ended up going with the central location. We choose a stove that didn't need a lot of clearance from the wall (Jotul Castine) and made the hearth flush with the surrounding floor to eliminate the tripping hazzard. As a bonus we get a lot more heat from the 20+ feet of double wall stovepipe inside the house.

 

[jzinckgra]

We had the same problem locating a stove in our house. We ended up going with the central location. We choose a stove that didn't need a lot of clearance from the wall (Jotul Castine) and made the hearth flush with the surrounding floor to eliminate the tripping hazzard. As a bonus we get a lot more heat from the 20+ feet of double wall stovepipe inside the house.

That's a great idea about using tile to flush it out with the surrounding floor. I was thinking about how a hearthpad would be a tripping hazard. But, don't you have to have a non-combustible under the tile itself and not your subfloor?

 

[RichVT]

That's a great idea about using tile to flush it out with the surrounding floor. I was thinking about how a hearthpad would be a tripping hazard. But, don't you have to have a non-combustible under the tile itself and not your subfloor?

It depends on the stove what is required underneath. My stove (with the bottom heat shield) only reqiures a non combustible SURFACE under the stove. Some reqiure a specific R value. Every hearth assembly is going to have wood at some point unless built on a concrete slab.

The tile does have 1/4" backer board under it to bring it up flush with the 3/4" hardwood.

 

[jzinckgra]

It depends on the stove what is required underneath. My stove (with the bottom heat shield) only reqiures a non combustible SURFACE under the stove. Some reqiure a specific R value. Every hearth assembly is going to have wood at some point unless built on a concrete slab.

The tile does have 1/4" backer board under it to bring it up flush with the 3/4" hardwood.

Good to know. I am deciding between the T6 and jotul F50. The F50 has tighter clearances and from what I can tell has both a bottom and rear heatshield. From the jotul manual:

The Jøtul F 50 TL requires one of the following forms of hearth protection if not installed directly on concrete poured on earth:
1) Any UL, ULC, or Warnock Hersey Listed Type 1 hearth board.
2) Any noncombustible material.

It would seem putting the stove on tile would be fine.

 

[wacnstac]

Let me ask another question related to this. Let's say you do a corner install on a 12/12 pitch roof and in order to hit the 10/2 rule, the amount of chimney that is outside and exposed to the cold is more than the amount inside (assuming all double wall chimney). Can this lead to drafting problems caused by the higher amount of chimney exposed in the colder temps?

 

[Ashful]

We have 12/12 pitch roofs on our house, and various chimneys penetrating at the ridge, soffit, and even one in-between the two. One penetrating at the soffit and extending up 12' is not nearly as offensive as you might picture in your head. No pictures handy at the moment, but I've posted enough that surely someone can dig up a posted photo of the three chimneys I have on the rear of my house.

 

[DAKSY]

Let me ask another question related to this. Let's say you do a corner install on a 12/12 pitch roof and in order to hit the 10/2 rule, the amount of chimney that is outside and exposed to the cold is more than the amount inside (assuming all double wall chimney). Can this lead to drafting problems caused by the higher amount of chimney exposed in the colder temps?

It's possible that you may have some issues at initial start up, trying to get the draft going, but there are a couple of ways to overcome that problem. One would be to start with a "top down" fire. That heats the the exhaust gases & the chimney slowly. Once the fire gets established, draft should be a non-issue. Another way would be to "Prime" the chimney with awad of paper or a torch. Once you got your winter burn going, I doubt that you'll have any issues even if you shut er down to clean the firebox. The warm air from inside your house will continue to flow thru the connector pipe & chimney, preventing too much of a cool down...

 

[wacnstac]

It's possible that you may have some issues at initial start up, trying to get the draft going, but there are a couple of ways to overcome that problem. One would be to start with a "top down" fire. That heats the the exhaust gases & the chimney slowly. Once the fire gets established, draft should be a non-issue. Another way would be to "Prime" the chimney with awad of paper or a torch. Once you got your winter burn going, I doubt that you'll have any issues even if you shut er down to clean the firebox. The warm air from inside your house will continue to flow thru the connector pipe & chimney, preventing too much of a cool down...

So it doesn't matter if you have more chimney on the outside than you do on the inside?

 

[Backwoods Savage]

So it doesn't matter if you have more chimney on the outside than you do on the inside?

If it matters, we have a huge problem. We have less than 2' inside and the rest is outside. Like Jake, we like the tee outdoors where we can just remove the cap and clean the chimney from the ground rather than climbing up on the roof.


For the OP: As for lots of SS chimney on the outside, I've never considered a chimney to make the home look bad. It is simply a necessary part of the home. And I don't see how a chase would look bad either. The chase can have the same type siding as is on the house. Speaking of the chase, many claim lots of us need one because of so much chimney exposed to the cold outdoors. We've never had a chase on any of our chimneys and we've never had a drafting problem.


On the hearth, do keep in mind which stove you will be installing. Just yesterday we watched a video showing a fellow loading his stove. He was down on his knees and still had to bend awkwardly to put wood in the stove. When you get a bit of age on those bones or an injury, it sometimes is not fun at all to have to bend to put wood in. Or even bend really low to even see inside the stove. This is why we built our hearth 16" high. Now when we load our stove, we sit on a chair and can see right into the firebox and loading is much easier. And with the 16" raise, there is no trip factor as was mentioned above.

 

[jzinckgra]

If it matters, we have a huge problem. We have less than 2' inside and the rest is outside. Like Jake, we like the tee outdoors where we can just remove the cap and clean the chimney from the ground rather than climbing up on the roof.


For the OP: As for lots of SS chimney on the outside, I've never considered a chimney to make the home look bad. It is simply a necessary part of the home. And I don't see how a chase would look bad either. The chase can have the same type siding as is on the house. Speaking of the chase, many claim lots of us need one because of so much chimney exposed to the cold outdoors. We've never had a chase on any of our chimneys and we've never had a drafting problem.


On the hearth, do keep in mind which stove you will be installing. Just yesterday we watched a video showing a fellow loading his stove. He was down on his knees and still had to bend awkwardly to put wood in the stove. When you get a bit of age on those bones or an injury, it sometimes is not fun at all to have to bend to put wood in. Or even bend really low to even see inside the stove. This is why we built our hearth 16" high. Now when we load our stove, we sit on a chair and can see right into the firebox and loading is much easier. And with the 16" raise, there is no trip factor as was mentioned above.

yes, we are planning on putting the same siding on the chase as the house. We'd do without the chase, but covenants require it Also, how would you brace a 13' high chase. I think the added bracing would make it look preety unpleasing to the eye.

 

[DAKSY]

yes, we are planning on putting the same siding on the chase as the house. We'd do without the chase, but covenants require it Also, how would you brace a 13' high chase. I think the added bracing would make it look preety unpleasing to the eye.

I'm thinkin that you're gonna have 3' of pipe exiting the top of the chase, so 10' of framing should be pretty rigid using LONG framing members...

 

[DanCorcoran]

I have 12/12 pitch and a corner install. I used single-wall flue inside to maximize heat transfer. I don't have a problem with a lot of exterior stainless, but it's just a matter of personal taste.

 

[rideau]

The chimney pipe matches the tree trunk on the other side of you house...

 

[jzinckgra]

Last question: we have to have a metal, non-combustible chimney chase pan on top of the chase. The chase will be built at least 3' above the roofline. Does the chimney then have to be another 3' above the chase pan or can it be lower?

 

[Ashful]

Last question: we have to have a metal, non-combustible chimney chase pan on top of the chase. The chase will be built at least 3' above the roofline. Does the chimney then have to be another 3' above the chase pan or can it be lower?

Chimney usually only protrudes a few inches above the chase.

 

[jzinckgra]

Well, we've gone back to looking at putting the stove into the corner with ~13' exposed pipe. Our installer is concerned about high winds and/or snow tearing it down. I have asked our builder to consider building a chase ~6' high with the rest of the pipe sticking out. This may look weird, but I would think the chase would provide the needed support for the pipe. Or forget the chase all together and just brace the pipe well enough. We are building on a hill and there will be some wind, but not terrible.

 

[DanCorcoran]

The chimney in my photo gets 30-40 mph gusts on a regular basis, with no problem. Those steel braces are all that's needed.

 

[jzinckgra]

well, one stove shop says putting our stove into a corner with our 12/12 roof pitch can't/shouldn't be done. They're claiming that cutting a hole so close to the edge of the roof could be a problem, but they are not comfortable erecting 13' of pipe more due to being able to do it safely. Our only other option is to go back to the center of the room, but this does not seem the best as it takes up too much floorspace. Arh! We may not be able to have a woodstove at all after all this and I've got tons of free wood, making it that much more frustrating. We'll see what another stove shop says.

 

[Ashful]

I guess I'm missing something to this story. I see chimneys built thru the soffit of 12/12 pitch roofs every day. I'm literally surrounded by them, and I'd be willing to bet you are, as well.

 

[jzinckgra]

I guess I'm missing something to this story. I see chimneys built thru the soffit of 12/12 pitch roofs every day. I'm literally surrounded by them, and I'd be willing to bet you are, as well.

yes, but are they erected to code? We need to have ~13' of exposed pipe. I don't see the issue either, as long as it's properly braced. Putting a hole in the ceiling where we'd like it also baffles me, as I don't see the problem. I need to ask our builder why he's not liking that location.