In to a basement remodel and after reading NFPA 211 regarding clearances I'm lost. I have a Hearthstone wood stove connected to a lined masonry chimney that was setting on a concrete basement floor against a block wall prior to the remodel. The hearth will be a wood platform with plywood top covered by backer board and slate tile grouted on top, my stove has the keg kit. The back wall will be 7/8" metal furring track with 3/4" rigid insulation in between the tracks, then covered with 3/4" plywood topped with backer board, wire lathe, mortar skim coat and finished with cultured stone. My question is the clearance I need around my double wall flue pipe where it connects to the masonry chimney with regard to the plywood and backer board, the best I can figure trying to understand NFPA 211 is 6", but I'm not positive. Also does anyone see a problem with my hearth design with regards to NFPA 211. And this is my first post, glad to find a forum to help me understand the NFPA.
Hearth Design
- Thread starter woodjdieter
- Start date
-
Active since 1995, Hearth.com is THE place on the internet for free information and advice about wood stoves, pellet stoves and other energy saving equipment.
We strive to provide opinions, articles, discussions and history related to Hearth Products and in a more general sense, energy issues.
We promote the EFFICIENT, RESPONSIBLE, CLEAN and SAFE use of all fuels, whether renewable or fossil.
- Status
Use the manual for the stove. It should have all the requirements listed. NFPA 211 is to cover "anything else" or unlisted stoves.
The manual is the boss. NFPA 211 picks up the pieces.What stove are we talking about?? (hearthstone). Hearthstone generally has pretty good manuals.
And welcome to the forum.
The manual is the boss. NFPA 211 picks up the pieces.
And welcome to the forum.
Owen1508
Minister of Fire
Which model stove is it? Which system are you using in the NFPA for the connection to the masonary chimney (Chapter 9)? What connector are you using? Is it listed for a wall pass through? As far as the wall you are building for behind the stove are you trying to reduce the clearances with it? Your measurements will be to the backerboard as your closest combustable, from the rear of the stove.
Welcome. We'll need to know which Hearthstone model this is and what is the keg kit? (Is it a beer chiller in the summer? 
) Did you mean the short leg kit? Most Hearthstone stoves require more insulation for the hearth than what is proposed, especially with the short leg kit.
) Did you mean the short leg kit? Most Hearthstone stoves require more insulation for the hearth than what is proposed, especially with the short leg kit.Thanks for the welcome's. It's the Heritage model, the legs are 5" tall, and yes the manual has all the stove clearances, but it doesn't have anything regarding the chimney connection(that I can find). The connection from the stove to the chimney is an 8" stainless thimble bedded in refractory cement passing from the tile liner through the chimney block and then through a 12" block wall. The stove pipe is 6" double walled and it is inserted all the way to the chimney tile liner and the gap between the double walled stove pipe and the ss liner is sealed with refractory rope. The new wall behind the stove that I'm attaching to the 12" block wall is more for aesthetics than reducing clearance. What I'm trying to figure out is after extending the SS liner to account for the new rear wall and cultured stone facing, what clearance do I need radially around the liner extension to any combustibles in the new wall.
The Heritage has an ember-only protection requirement so your hearth plans are good to go. I am not understanding the thimble. Are you using 8" class A insulated pipe for the thimble through the 12" block wall or just an 8" stainless single wall pipe?
Owen1508
Minister of Fire
Ok re-reading it sounds like all you are doing is added a new aesthetic wall to a already installed Heritage stove. So you are just needing to find out how close you can build the wall to the chimney connector that you had to extend to the setup for the new wall. Correct?
Begreen, the thimble going through the 12" block wall is 8" single wall SS pipe embedded in refractory cement and appears to be either 14 or 16 gauge. I forgot to explain that the chimney block work is adjacent to the 12" block work making the total 8" ss thimble approximately 18" long, in case that is relevant. The double wall stove pipe passes all the way through the thimble to the chimney tile liner and the difference in diameters is sealed with a rope gasket wound around the dbl. walled stove pipe.
Owen 1508 you are correct, this is an existing installation and I'm adding a new backwall. I'm not sure how close the 3/4" plywood and cement board on the new wall can be to the increased length of the ss thimble. I'm estimating I'll need to add 2-3" to the existing ss thimble length . When we installed the stove I had them (the company that I purchased the stove from also installed it) use telescopic dbl. walled pipe on the horizontal section to accommodate my future plans for the new wall.
Owen 1508 you are correct, this is an existing installation and I'm adding a new backwall. I'm not sure how close the 3/4" plywood and cement board on the new wall can be to the increased length of the ss thimble. I'm estimating I'll need to add 2-3" to the existing ss thimble length . When we installed the stove I had them (the company that I purchased the stove from also installed it) use telescopic dbl. walled pipe on the horizontal section to accommodate my future plans for the new wall.
JA600L
Minister of Fire
Owens corning makes a nice "insul pink" foam board designed for furing strips. Theirs is r 7.5 2'×8'x1.5".
I'm starting the same process as you.
I'm starting the same process as you.
JA600L, as part of the basement remodel I have enough 7/8" metal "hat track" and the pink stuff leftover that I used in other areas. I'm installing the hat track on 12" centers instead of 16" so I'll trim the rigid foam to fit. 12" may be overkill, but I don't want to take any chances with the cultured stone moving and the mortar cracking.
This sounds like a homebrewed thimble, so I am not sure what the clearances should be. Double wall connector pipe is not designed to go through a wall. Is the double-wall pipe going through the 8" stainless sleeve regular stove connector (interior) pipe, like M&G DVL?
Owen1508
Minister of Fire
You are trying to build a wall to a stove pipe connector and they are not designed for that.
The best solution,IMO, would be to put in a proper sized thimble that passed through both the new wall and the masonary chimney wall, and use one of the methods in Fgure 9.7.5
I would not want any wood hovering over a stove connector too close. It might work for a year,2 or 5 but it could ignite once it dries out and reaches combustion temp.
The best solution,IMO, would be to put in a proper sized thimble that passed through both the new wall and the masonary chimney wall, and use one of the methods in Fgure 9.7.5
I would not want any wood hovering over a stove connector too close. It might work for a year,2 or 5 but it could ignite once it dries out and reaches combustion temp.
Owen1508
Minister of Fire
You have no other option then using combustible building materials. Could you attach the cement board to the metal strips and then lathe, mortar and stone. That would make it 100% non combustable. If you use all non-combustible then you wouldn't have tochange the thimble or be concerned with clearances. Just a thought.
Owen1508
Minister of Fire
Yeah. That's why I excluded it. Just the cement board attached to the metal furring then lathe, mortar and stone. The air gap may help keeping the mortar/stone from cracking some I would even leave the top and bottom of the new wall with a 1-2 " opening for air flow.
EDIT ADD: I believe it is being attached to a block wall as well so the metal furring wouldn't matter much being directly behind the stove as well.
Last edited:
I think the question is, how far away from the proposed thimble should the insulation be? I can't answer that question because double-wall connector pipe is not supposed to penetrate a wall.
Last edited:
Owen1508
Minister of Fire
Exactly. Think it has to be (for safety) either a proper thimble needs to be added to include the new wall or the new wall has to be 100% non combustible.
If it were my set up or one I was doing it wouldn't be any other way. I think that is why he was having a hard time finding it referenced in the NFPA because it shouldn't be done.
Is it considered penetrating a wall even though the dbl. walled stove pipe is inside the thimble with approximately an inch of airspace around the circumference, between the stove pipe and the thimble?
When we purchased the stove the, we also purchased a ss flue liner, but with heavy snow on the roof the installers couldn't safely install the liner so we opted to use the existing tile lined chimney temporarily and put the ss liner in at a latter date. Maybe that explains my situation better. I still plan on having the ss liner and cap installed in the existing flue.
Not the Heritage from a few years ago that I owned. It has nasty hearth requirements that did not allow for just tile on wood. Not even tile on durock on wood. You needed to get fancy.
Last edited by a moderator:
the way you are connecting to your liner is not acceptable, You need to get an 8 to 6 reducer and attach the double wall to that with the right connector supplied by the manufacturer of the double wall pipe. The way you are doing it now you are putting fresh air into the flue through that outer layer or double wall pipe that is just asking for trouble. as far as clearances it is 18" from single wall 6" from most double wall but the pipe should have that spec. Just wondering why you put in an 8" liner for a 6" stove also.
oh i see you dont have the liner in yet i missed that some how. That makes more sense but you still cannot hook it up the way you described. it is not a safe way to do it
Yes, I was surprised to read this too. It appears they must have made some mods and retested. This is from the 2012 manual:
HEARTH REQUIREMENTS AND FLOOR PROTECTION
Combustible flooring must be protected with a covering of noncombustible material (slate, marble tiles, or other noncombustible material can be used
for this purpose). The floor protection must extend beyond the body of the stove at the minimum as follows:
LEFT SIDE 16” (41 cm)*
RIGHT SIDE 5” (13 cm)
REAR 2” (5 cm)**
FRONT 16” (41 cm)*
With the liner in place you will have a fairly long horizontal snout heading to the tee in the chimney. Be sure that this horiz. section is pitched upward with a slope of 1/4" per ft or more. Smoke does not like to go downhill. If it were me, I'd remove the 8" stainless sleeve and replace it with a 24" length of class A pipe. You will have to consult with the local inspecting authority and make the call. They may decide to allow you go with a long tee-snout in single wall. If so, ask how far away your would need to frame the hole and have no insulation within the framed area. My guess is they will say 12" from the sleeve and the sleeve must project into the room past the finished surface. But that is just a guess.
Sounds like an awful lot of work to squeeze in a few scraps of foam when everything else is non-combustible. Given you already have a non-combustible block wall and a non-combustible concrete floor, and you're already doing masonry with the stone, I think I'd be tempted to build the hearth out of concrete block, then cover with slate and apply the cultured stone directly to the block wall. Then do what ever you want with the stove as it's all non-combustible.
I doubt those few strips of 3/4 inch foam over the width of a chimney are going to make 2 cents worth of difference in the end and by adding it and those bits of wood for a hearth, then you have to start treating everything like its made of wood. ...additional clearances, air gaps between stone and wood, added insulation, etc.
I doubt those few strips of 3/4 inch foam over the width of a chimney are going to make 2 cents worth of difference in the end and by adding it and those bits of wood for a hearth, then you have to start treating everything like its made of wood. ...additional clearances, air gaps between stone and wood, added insulation, etc.
- Status
Similar threads
