Need simple but safer outlet to chimney

[tomottoe]

Hi
I moved into a house and am looking to install a woodstove. The house was built in 1992 and never had one hooked up. Right now, there is a ceramic pipe 10 inches diameter and about 5 feet above the floor, exiting the wall horizontally to the chimney outside (there is no furnace so this chimney is solely for this pipe). The problem is the sheetrock comes right up to the walls of the pipe. I know how hot that pipe is going to get; I don't necessarily expect the wall to combust but it doesn't seem terribly safe. Is there some sort of collar I can insert around the pipe to diffuse the heat before it contacts the wall, or is there an alternative pipe material that can safely mate with the wall? My cousin who is a contractor suggested cutting out the sheetrock around the pipe and replacing with cement board but I don't think that's going to look very good.

Any suggestions?
Thanks very much
--Tom

 

[MountainStoveGuy]

Ceramic pipe? Hmm can you please post a photo? if you dont know how you can email it to me at [email protected] and i will post it for you.

 

[MountainStoveGuy]

A starting point on this thread is at least if we know that you have a masonry chimney, and you want to put a high efficiency epa stove on it, it would have to be lined and insulated with a 6 inch liner. I would think that you would have a trim piece for the "pipe coming out of the wall" that would connect to the liner, then you would go with double wall black pipe down to the stove. That double wall needs to be 6 inches from any combustable. So hopefully your thimble protrudes at least that far.

 

[Corie]

When he says ceramic pipe, I believe he's referring to clay chimney liner. I've seen this set up in a few new construction houses around here, but the sheetrock touching the edges of it is definitely not safe.

 

[BrotherBart]

When he says ceramic pipe, I believe he's referring to clay chimney liner. I've seen this set up in a few new construction houses around here, but the sheetrock touching the edges of it is definitely not safe.

Yeah, that's what I'm thinking. I have that setup in the basement. 8"clay thimble going through the concrete block wall to a clay tiled chimney liner.

I have the F100 burning into it but every time I look at it, it just screams "WOOD FURNACE!" at me.

 

[Michael6268]

Sounds llke you are talking about a clay thimble. If so just cut back the sheet rock 2 inches all the way around. This would be a good time to look at what was behind the sheetrock. Hopefully masonry and nothing combustable within 2 inches. If all looks good your good to go! Should be able to find a trim collar to cover the gap left.

 

[begreen]

I would like to understand how to set up a stove for a straight-out-the-back installation. We are contemplating a remodel which would relocate our F3CB. If we go this route, I'd like to vent the Jotul straight out the back into a boxed and insulated exterior chimney. But I need to understand the thimble details. How does one do this?

 

[MountainStoveGuy]

I thimble detail with simpson duravent chimney would be,
wall thimble
18" piece of class A
Class A "T"
"T" support bracket
Adapter to go into they class a to take it to connector pipe. These demisions of pipe would be used for double wall black only, and no thicker then a wall of 2x6 studs.

 

[webbie]

Sounds llke you are talking about a clay thimble. If so just cut back the sheet rock 2 inches all the way around. This would be a good time to look at what was behind the sheetrock. Hopefully masonry and nothing combustable within 2 inches. If all looks good your good to go! Should be able to find a trim collar to cover the gap left.

I don't think 2" is the clearance for masonry thimbles.....I think sheet rock is classified as combustible, which would mean cut it WAY back!

I agree that cutting it somewhat back will help determine if the clearances around the clay thimble are correct - if my experience is any judge, they are not!

The wall connection is VERY important and often the cause of fires. There is an article entitled "Passing through a wall" at the page:
https://www.hearth.com/what/specific.html

Read it for the basics....perhaps Elk can chime in....

If a person really want to make a white wall behind a stove, I think they'd have to use durarock or similar material in place of the sheetrock for at least a foot around the crock. Inside the wall, a large masonry "patch" around the crock is needed.

 

[elkimmeg]

The paper facing on sheetrock is considered combustiable even fire coded 5/8" sheet rock. What would worry me is
how it is attached? Strapping attached to the bricks or blocks ? More combustiables directly attached to a surface, they should not be. 10 " clay thimble is quite large, makes me believe your flue size is 8/12 or 12/12. Is the chimney exposed to the outside wall?
If this is true then no 6" collar stove can be installed without a full liner that is 2003 NFPA211 code. However an 8" flue collar stove can be( without a reline) A few models come to mind VC Encore, Defiant. and the large Dutchwest.

It is possible that the sheetrock is covering up a nice brick facing chimney. I think your cousin has the right idea. Cut out the sheetrock and examine what you have. It is possible to install cement board and skim coat plaster over it. That would take care of the paper facing issue of sheetrock. The second issue is to find out how the sheet rock is attached. Wood strapping or 2/4 in direct contact is a no no. One could remove them and use metal high hats and cement board. Again you could find a nice looking brick face which you would want to expose. Your first step is to cut out an examination hole. If you need instructions of how to go about it, I or others can advise, so that minium patching will be required to replace it. I am willing to bet there is wood behind the sheetrock. The distances of that wood, in relationship to the flue and thimble are critical, to advising you safe code compliant options.

 

[stovepipe?]

in that article one of the options mentioned is a section of class A chimney used as a thimble. It indicates that you still need a 9" airspace clearence around the section of class A which extends from the masonry chiimny into the room. why should that be? doesn't class a chimney only require a 2 inch clearance to combustables?

 

[MountainStoveGuy]

That clearance would be the allowance for the connector pipe attaching to it.

 

[elkimmeg]

Code wise in most cases the clay thimble is incased in brick block and motar, it is not usually sticking out.
99% of all cases the clearance of clay is a non factor The clay cannot be used for passage threw a combustiable wall.
It may be possible to use double wall or class A pipe that will fit within the clay outlet that will satisfy code. However passing threw a combustiable wall requires the manufactures thimble to comply with that system of pipe. A catch 22 issue here. It would really help to know what is behind that sheet rock, how it is attached, and what size clay flue

 

[berlin]

clay thimbles can pass through combustable walls providing they are surrounded by a minimum of 12" masonry; however, it does not look like it is surrounded by anything but sheetrock in this case.

 

[Michael6268]

Craig. 2 inches in my neck of the woods is all that is required by code. Sheet rock is never going to catch fire with a 2 inch air gap......

 

[MountainStoveGuy]

I think the confusion here is about the 2 inch clearance. There is a 2 inch clearance that needs to be maintained on a verticle run of class a chimney. At some point you have to connect that class a chimney to connector pipe. At that point you have 2 choices of connectors. Single wall and double wall. Single wall has a 18 inch clearance and double wall has a 6 inch clearance. So if your going through a wall with class a and your next piece inside is a 90* elbow, then your class a will have to come through the wall far enough for that 90* to make clearance.

 

[tomottoe]

Hi guys
thanks for all the input--I had a crazy work week so I'm finally getting back to this problem. I have attached a picture of the setup.

The pipe is painted black but is definitely made of terracotta or clay. The left, top, and right clearances to the studs are 6-7", clearance to the bottom stud is 4". There is some fireplace gasket glued around the pipe which I guess was there to reduce draft through the sheetrock.

The pipe is 10" outside diameter, 8" inside diameter--so I'm not sure which one you refer to when checking code compliance.

I clearly don't have the 9 inch clearance quoted in the Passing thru Walls article that Craig Issod referred to. But does the cement board idea still sound viable? If I installed it, floated plaster on it to create a smooth surface, could I then use regular house paint to cover to match the wall, or would I have to use stove paint?

thanks again
--tom