Clearances to Combustibles/Hearth Surround Question

[richg]

Howdy folks,

I'm looking at buying a new stove, however, the choices are somewhat limited by safe clearances to combustibles. Right now, there's a stove on the hearth pad that the manufacturer specifies a minimum of 7 inches from the back corners of the stove to the wall (I'm using double-wall Selkirk Stove Pipe). Some stoves specify longer distances which will knock them out of contention. My question is, would the construction of this hearth surround classify as a "combustible surface"?

From the outside to inside, the surround is comprised of:

1. Porcelain tile
2. Cement board
3. 1 x 4 furring strips, 16 inches on center (this is what concerns me).
4. Cinder block wall

There is no air gap at the bottom or top of the tile. My practice is always to err on the side of safety...Please let me know your thoughts. PS, sorry about the tragic illustration....

 

[bholler]

yeah I am afraid it would be classified as combustible because of the furring strips sorry.

 

[begreen]

A way to make non-combustible 1" furring strips is to double-up two layers of 1/2" x3" x XX length strips of cement board. But in this case why not just tile directly onto the cement block?

 

[begreen]

The PE Summit is 6" with double-wall if that helps.

 

[BobUrban]

Is this hearth already in place? If not see BG's post above or if you want to get it out away from the wall a bit DBL up the cement board(durarock) and attach it with mortar directly to the wall - tile over that.

 

[cableman]

If what you show is there now then you have to figure the clearance to the would furring strips and then the hearth has to come past the front of the door 16". Porcelain tile and cement board are not flammable so it doesn't matter how close you are to those just as long as your the recommended distance away from the wood furring strips! Correct me if I'm wrong anyone! Thats the info i got while doing mine but i went from the none combustibles distance anyway.

 

[begreen]

Correct, the distance is measured to the nearest combustible.

 

[bholler]

no it is from the face of the wall not the combustible materials. this is due to the fact that the tile and backer board will transfer the heat through very well directly to the furring strips. there is a slight clearance reduction when you get up to 4" nominal such as brick but I cant remember off hand without looking it up. but the 3/4" or so in this situation will not do anything

 

[bholler]

I think it should be to the nearest combustible but I believe code says otherwise I will look it up later

 

[richg]

Folks, thanks for your replies. I figured this setup would be a combustible surface and am not going to take any chances with it. No worries, the Blaze King Princess has a 7-inch clearance to combustibles from the back corners with the optional heat shields and blower. It will be some strong medicine to swallow the price of that stove, but this is par for the course in burning wood. Between chain saws, splitters, safety gear, splitting mauls, gasoline, stoves wood etc., I'm wondering when the saving money part kicks in

 

[mstoelton]

The saving money part kicks in when you don't write a big check to the power company/oil supplier/gas company at the end of each month. Besides you can't count the money you spend on toys like chainsaws, splitters, mauls, and such in the costs of this game! Those are TOYS! Just Kidding!

 

[begreen]

no it is from the face of the wall not the combustible materials. this is due to the fact that the tile and backer board will transfer the heat through very well directly to the furring strips. there is a slight clearance reduction when you get up to 4" nominal such as brick but I cant remember off hand without looking it up. but the 3/4" or so in this situation will not do anything

It is from the nearest combustible. If the wall was sheet rocked, then it would be to the wall surface because sheetrock is considered a combustible. In your example actually the cement board does have an R=.20 to .39 insulation value that slows down the transfer of heat. But NFPA does not account for these small variables. 4" of brick will achieve a 33% reduction I think (not at my computer right now), but only if the stove mfg. permits an NFPA 211 reduction in the documentation and that min. space would be 12" unless tested and specced by the mfg.. Regardless it sounds like you will be fine richg. Enjoy the new heater.

 

[richg]

Happy Saturday Folks:

A few days ago I posted a thread about clearances to combustibles. The problem is that I want to buy a new stove, however, choices are limited by clearances to combustibles. Depending on what you think, this may open up some new stove options. Refresher: hearth surround consists of, from the outside in:

1. Porcelain tile
2. Cement Board
3. 1 x 4 Furring strips
4. Cinder block wall

The furring strips are considered combustible, and given the corner install, this is limiting m choice of stoves. What I did was locate the furring strips under the tiles based on the install of 16 inches on center, and here are photos of where they are located. If I were to bust out the tiles, remove the furring strips and install cement board so that the replacement tiles were flush with the existing, would that negate the combustible clearance problem? I have plenty of tiles left over. If you think this would work, do I have to remove all four of the furring strips in the pictures or just the ones that are currently within the "red zone"? I can do the job in a weekend with no trouble, and would rather spend the time doing it and open up additional stove options. Please let me know your thoughts, thanks.

 

[bholler]

just removing the ones in the "red zone " should work fine. don't forget to measure up diagonally to that wood trim above the tile it looks a little close to but it might not be hard to tell

 

[begreen]

This is for the Quad 4300 with double-wall connector, correct? If so that stove has the closest corner clearances on the market to my knowledge. The step top requires only 2" corner clearance according to the manual. I could be missing something, but so far I don't see where there is a clearance issue here.

 

[kuribo]

Not completely sure, but since the furring strips are behind the tile, which is non-combustible, aren't you ok? I always thought the rule was to the first surface....

 

[begreen]

The rule is to the first combustible surface.

 

[Lumber-Jack]

Not completely sure, but since the furring strips are behind the tile, which is non-combustible, aren't you ok? I always thought the rule was to the first surface....

No. Clearances are to combustibles period! Unless you have a proper vented heat shielding, which means a shielding that has air flow thru top to bottom, in which case you can reduce your clearances according to the stove specifications. That is not the case with those furring strips enclosed behind the cement board.
Of course he might still be OK with the furring strips behind that cement board if he is meeting the proper clearance for that stove?

 

[Lumber-Jack]

Not completely sure, but since the furring strips are behind the tile, which is non-combustible, aren't you ok? I always thought the rule was to the first surface....

Just want to re-emphasize that this is where a lot of people go wrong on wood stove installations and has been attributed to a lot of house fires. I have personally seen where people have installed metal heat shielding behind their stoves and fastened the metal heat shielding to WOODEN 2x2s spacers Thinking that the non-flammable metal will stop the flammable 2x2s from catching fire. It just ain't the case. You have to use non-flammable spacer for heat shielding like that.

 

[begreen]

Breaking this thread into chapters is confusing as heck. Measuring off the existing stove is deceiving if it's being replaced. I merged the threads as most points have been covered in the original thread.

 

[kuribo]

I stand corrected!

Still, there is a big difference between attaching sheet metal directly to studs and having ceramic tile on cement board hung on studs.

 

[begreen]

True there will be a little insulation value with the tiled board, but there is no difference with regard to clearances. The stud is what is measured to unless the stud is metal.