stove wall shield

[new stove]

How can I find out if Cultured Stone (CS) is a safe wall shield for my new wood stove? I was originally planning to use real river stones but I decided that the CS was much lighter and easier to use. I was told by the stove retailer that with the real stone I didn't need to leave a 1" Air Space between the sheet rock and the wall shield (the stone) because the stone would absorb the heat of the stove. However, now I want to use CS I don't know if the CS, which is made out of cement, is going to absorb the heat like the real stone.
What do you think? Should I go back to using real river rock? If so, Will the stone and base be too heavy for the house? I am planning to place the stone in the corner of the living room which is located on the second floor.

 

[Corie]

First off, the dealertold you the wrong things. Real stone still requires that air space because there is little difference in its R-value and that of cultured stone.


If you want to use the cultured stone, which is fine from a materials perspective, give yourself that airspace, use cement board and then mortar the stone in place.

 

[new stove]

Master,

Does the cement board go on top of the sheet rock? My friend who is doing the work and works with rock & tile, says that the shet rock has to be removed & then the cement board goes up against the wall studs. Is he right?

 

[Corie]

The sheetrock can stay, but the cement board should be space 1" off of the sheetrock using non-combustible spacers like the ceramic ones that are commercially available.


Then attach the stones to that cement board.

Since you're going to be attaching A LOT of weight to the cement board, there is no way you'll be able to have an inch air space along the bottom which is required. You should leave part of it touching the ground.


I'm going to draw a sketch because I know I'm not explaining well.

 

[GVA]

Master,

Ahh grasshopper.... when you can snatch the cultured stone from my hand...... Then you will be ready..... :cheese:
Sorry couldn't resist that one.
I don't have an answer for you I would think you could go over that drywall but I'm not sure.
EDIT.... Corie your quick...... sensei (sp)????? ;-)

 

[Corie]

You'd probably be ok going right over it with the cultured stone, then mortar, then cement board and maybe a layer of micore and then the sheetrock.


The airspace evens things out, knocks down the conduction heat exchange from the stones to the wall and also slows down radiation a bit.




But before we got nuts here, what stove are you installing? If the stove is listed to be installed X distance from a combustible wall and you have X distance from the stove to the stone, then you don't need to worry about the airspace.

If you're building the stone wall shield because you're trying to reduce clearences to the wall, then you definitely should consider the airspace.

 

[Corie]

Hope this helps a little.

 

[new stove]

I am not trying to reduce the clearences, I just want cool looking river rock behind the stove. But... don't you need the clearences anyway, with or without wall shields?

OK I bought the Jotul F 400 Castine.

SP?

:question:
what...

 

[Corie]

ohhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh.




Nope, feel free to stick the cement board to the wall and then the stone to that. You'll be fine.

 

[elkimmeg]

BTW the clearance is measured from the comustiables ie the sheet rock and not the ccultured stones, if non combustiable. There is no penalty for exceeding the required distances only a failedl inspection, if they and not adhered to.

 

[wg_bent]

Elk, so your saying that if the wall surface material is not combustible, then you can get as close as you like? As long as it's not a combustible surface? I don't think that's what you intended... I know you better. The Castine manual will provide the clearances for combustible and non-combustible wall materials and those distances should not be exceeded. With a combustible wall behind the stone, the clearance values should be adhered to, and you should be fine just sticking the stone to the cement board. Remove the sheetrock, and replace it with the cement board, morter the stone or cultured stone to it, and install the stove per manual for non-combustible walls. Corie, that line up with what your saying? For added protection add the layer of micore behind the cement board.

 

[restorer]

Elk, so your saying that if the wall surface material is not combustible, then you can get as close as you like? As long as it's not a combustible surface? I don't think that's what you intended... I know you better. The Castine manual will provide the clearances for combustible and non-combustible wall materials and those distances should not be exceeded. With a combustible wall behind the stone, the clearance values should be adhered to, and you should be fine just sticking the stone to the cement board. Remove the sheetrock, and replace it with the cement board, morter the stone or cultured stone to it, and install the stove per manual for non-combustible walls. Corie, that line up with what your saying? For added protection add the layer of micore behind the cement board.

Warren,
You are right and wrong. You are using the new math. If the surface is noncombustible, you can get as close as you want, however, the distance to the combustible wall doesn't change. If you directly apply the non- wall to the combustible, it is a non reducing surface. Split hairs, but don't give the impression that the data is false. The measurement is from the combustible surface to the stove.

 

[elkimmeg]

Warren there is one other factor even if the wall is completely non combuctiable. Say like you cellar foundation wall. It is still a good idea to provide some space behind a free standing stove no less the 6" to 10" to alow heat dissipation and air convection .Though not spelled out in code, but still a good idea.

 

[wg_bent]

Elk, so your saying that if the wall surface material is not combustible, then you can get as close as you like? As long as it's not a combustible surface? I don't think that's what you intended... I know you better. The Castine manual will provide the clearances for combustible and non-combustible wall materials and those distances should not be exceeded. With a combustible wall behind the stone, the clearance values should be adhered to, and you should be fine just sticking the stone to the cement board. Remove the sheetrock, and replace it with the cement board, morter the stone or cultured stone to it, and install the stove per manual for non-combustible walls. Corie, that line up with what your saying? For added protection add the layer of micore behind the cement board.

Warren,
You are right and wrong. You are using the new math. If the surface is noncombustible, you can get as close as you want, however, the distance to the combustible wall doesn't change. If you directly apply the non- wall to the combustible, it is a non reducing surface. Split hairs, but don't give the impression that the data is false. The measurement is from the combustible surface to the stove.

Uncle, Not sure where your indicating where I'm wrong. I said... with combustible behind the stone, clearances values should be adhered to. Seems to be the same as what you said. I suppose the further clarification of Clearance value to the combustible surface could have been added regardless of the fact that there is 3" of stone in front of it. So even with a non-combustible surface if you put the stove dx away from the stone, the clearance will not be enough... Distance from the combustible needs to be adhered to.

 

[Gooserider]

I hope if I'm wrong that Elk will correct me, but here is my understanding... If you have a sheetrock over stud wall, the sheetrock is combustible, and the measurements would be to that. If the wall is cement board over studs, you would measure the distance to the combustible studs, not to the cement board.

If you put non-combustible material over the combustible wall surface, the thickness of the non-combustible material doesn't count when measuring clearances.

For example suppose the stove manual specified 12" clearance to combustibles - (to make the math easy) and you have a sheetrock over stud wall. If you put the stove 12" away you'd be legal, 11" away you wouldn't, and 13" away you'd be doing better than required. If you replaced the combustible 3/4" sheetrock with 3/4" non-combustible cement board, you could move the stove 3/4" closer to the wall, but no more because you still have combustible studs.

If you put 2" worth of non-combustible cultured stone OR river rock, (or bricks, or any other non-combustible equivalent) on top of the sheetrock, you would not have to move the stove, as the critical distance is STILL the 12" to the sheetrock, not the 10" to the new non-combustible exposed surface.

IOW, the key is the distance to the nearest COMBUSTIBLE surface, not just the nearest surface of any sort.

Gooserider

 

[mmichaud]

For what it is worth... I installed cultured stone behind my Jotul Castine stove. It was not that hard but it took a lot of time. Make sure that you fasten the cement board real well. You will also have to use metal lath over the cement board in order for the stone to have something to grab on to. I will attach a picture to show my stove and rock.

Mike

 

[thechimneysweep]

This might be one of those "Your Mileage May Vary" situations, but our service area spans several code jurisdictions, and they all read the wall shielding situation the same way:

If your non-combustible material is touching a combustible wall (with no airspace), it becomes part of the combustible wall. If your stove needed 8" clearance from the sheetrock, it now needs 8" clearance from the farthest protruding stone. If you replace the sheetrock with non-combustible millboard attached to the wall studs, you need 8" clearance from the millboard.

If you provide a 1" ventilated airspace between the combustible wall and the non-combustible material, clearances are measured to the combustible wall behind the airspace. The existence of the ventilated non-combustible material may even reduce the required clearance to the combustible wall behind, depending upon the manufacturer's listing.

 

[Harley]

If your non-combustible material is touching a combustible wall (with no airspace), it becomes part of the combustible wall. If your stove needed 8" clearance from the sheetrock, it now needs 8" clearance from the farthest protruding stone. If you replace the sheetrock with non-combustible millboard attached to the wall studs, you need 8" clearance from the millboard.

Not trying to be a PIA, but I'm not sure I follow this.... If you use noncombustible millboard as the example above, and it is touching a combustible (ie., the wooden studs), why doesn't that become "part of the combustible wall"?

 

[thechimneysweep]

It does. The stove in the example that required 8" clearance to the sheetrock would also require 8" clearance from the millboard that replaced it.

 

[Harley]

"If your non-combustible material is touching a combustible wall (with no airspace), it becomes part of the combustible wall. If your stove needed 8” clearance from the sheetrock, it now needs 8” clearance from the farthest protruding stone. If you replace the sheetrock with non-combustible millboard attached to the wall studs, you need 8” clearance from the millboard. "

It has to be me a little slow on the up-take, and again... not trying to beat a dead horse... but still not getting it..... If in the case of sheetrock, you would have to be 8" from the stone (because the stone is attached to the sheetrock, and becomes part of the combustible wall)... why wouldn't the millboard and attached stone be considered "part of the combustible wall", since it's attached to the combustible framing? I understand the reality of the fact that the heat isn't going to get that far back.... I guess what I'm not making the connection with, is why you would have to be 8" from the stone if you had sheetrock behind it, versus 8" from the millboard in the other case.

 

[Hogwildz]

For what it is worth... I installed cultured stone behind my Jotul Castine stove. It was not that hard but it took a lot of time. Make sure that you fasten the cement board real well. You will also have to use metal lath over the cement board in order for the stone to have something to grab on to. I will attach a picture to show my stove and rock.

Mike

Is that a thermometer on the horizontal pipe near the wall thimble? If so, your not going to get a true accurate reading there.

 

[mmichaud]

"Is that a thermometer on the horizontal pipe near the wall thimble? If so, your not going to get a true accurate reading"

Yes it was, but I moved it about 14 inches off the top of the stove. That was one of my learning curves I went through with the new stove. I am slowly catching on the ways of wood burning.

Mike

 

[elkimmeg]

To all its not so much a code issue but the way the indivual inspector interpets code I interpet it to combustiables not including non combustiables attached in front.
I also can see that the non combustiable in front can act to transfere heat to the combustiables behind them My take is heat is lost or further isolated dissipated traversing the non combustiable stove and poses no more risk to the sheetrock behind it. But again that's my interpetation the chimney sweep is not wrong either

You asked the question here why not ask the guy that will sign the installation approval?

 

[thechimneysweep]

Harley, now I see what you're asking. I guess I wasn't too clear there: what I was describing was a situation, as suggested in another post above, where there was no stone wall, just replacing the sheetrock with non-combustible millboard. If you just did that, the inspectors in our code jurisdictions would consider it a combustible wall, and measure clearances from the surface of the millboard. If you then added stone that touched the millboard, the measurement would be from the furthest-protruding stone, same as if you'd applied the stone to the sheetrock.

Elk, you've hit the nail on the head there. There are some code issues that the various code departments we deal with DISAGREE on, so our installers sometimes need to know what jurisdiction they're in to know what will be needed to pass inspection. It seems to me that the best advice to give forum visitors with code questions is to consult their local code authority.

 

[Hogwildz]

"Is that a thermometer on the horizontal pipe near the wall thimble? If so, your not going to get a true accurate reading"

Yes it was, but I moved it about 14 inches off the top of the stove. That was one of my learning curves I went through with the new stove. I am slowly catching on the ways of wood burning.

Mike

We all are that setup & the stone looks damn nice BTW!