Metal Studs for NFPA 211 Protected Surface

[fjordrr]

Hi, new here Just put a deposit down on a Jotul 400 Castine (got talked out of the 500 Oslo as overkill). I am doing a corner installation of which one wall is interior, one wall exterior. I am trying to reduce clearance to wall as much as possible (for space & to miss a fire sprinkler pipe).

I have read reams of valuable info on this site, but am still a mite confused. For 4' of the exterior wall of my corner installation, if I go with: river rock->cement backerboard->metal studs WITH R13 insulation->plywood->cedar shingles - would this still be considered an NFPA 211 protected surface? As there really isn't any air space due to the insulation?

I think I'm OK with the 4' of the interior wall - as I can go river rock->cement backerboard->metal studs w/ air space->sheetrock.

Any input is appreciated! As the wall clearance difference is 5" (11" vs. 6" according to Jotul).

 

[BXTF]

Sorry I can't help you with your question. I am all so installing the F400 in a corner I put up a non-combustible wall because space is a big concern for us, like you said 11" to 6" is a lot. I do have a question for you, what size hearth pad are you going to install? My installer is putting in a 54" pad and I keep thinking I can go smaller. Just want to here from someone who is doing and thinking the same as us. Thanks
PS The stove is going in this Monday

 

[fjordrr]

Thanks for your reply. Did the non-combustible wall you built allow you to get it down to the 6" clearance instead of 11? If yes, what did you have built?

re: pad size for the 400 Castine - min specs in their manual call for 44" min depth, 42" min. width. I haven't made the final size decision, but I do know I will be doing a 2-tier "stepped" design - found some nice examples on this site. So I'm thinking 44" for the top level, then perhaps an additional 10" for the second level. Haven't decided whether the 2nd level will be flush to the floor, or raised. Flush gives back more space into the room while raised allows seating directly in front of the stove. I have found over the years that additional space in front of a stove or fireplace is quite handy, so I don't want to short myself there, even if it is within spec.

Here's one nice photo: https://www.hearth.com/gallery/pics/woodcoal/source/jot3etc.html

 

[Highbeam]

Are the Jotul's unique somehow in that they give you some kind of credit for a heat shield on the wall? All the stoves that I've looked at listed a "clearance to combustible" which could be anything, even plywood. No reduction was ever given for some sort of fancy heat shield on the combustible surface since the clearance will always be measured to the first combustible surface.

Are you guys talking about framing up an entire wall with, rebuilding it, with nothing deemed combustible in it? Would this allow you to place the stove immediately adjacent to it? Like a concrete poured wall?

 

[begreen]

Jotul does allow a clearance reduction when there is an NFPA 211 wall shield involved. The shield as proposed, is not an approved or tested design. It might be ok, but being untested there is no spec. You could ask your inspector if he/she would approve it. However, the currently proposed design certainly could work with a minor modification.

You don't need to use the metal studs unless they are already in there. To make the wallshield proper, there needs to be an air gap of 1" between the studs and the backerboard. This airspace needs to have an opening at the bottom and at the top that will allow cooling air to enter at the bottom and heated air to exit at the top. Backerboard spacers can be created by using doubled up, 4" strips of durock mounted onto the studs. (Be sure to use the original Durock and not the next generation product.)

Here's a document from USG on how to build an NFPA 211 wallshield out of durock cement board:
(broken link removed to http://tinyurl.com/nmmt3)

 

[BXTF]

"Thanks for your reply. Did the non-combustible wall you built allow you to get it down to the 6" clearance instead of 11? If yes, what did you have built?"

I really won't know till Monday when they install the stove. I built a box out of plywood the same size as the stove and if I measured right the clearance should be about 7" from each corner.

The wall I built was made from durock with one inch ceramic spacers and a one inch space above where the hearth pad will be all around.

I'll let you know on Monday how I make out.

 

[fjordrr]

Thanks everyone for your further replies. I guess I am talking about building a complete non-combustible wall, at least on the interior wall of the corner for the woodstove. I am framing in a 4' hallway opening to extend a wall for the stove placement, so I can use whatever I like there.

The other corner wall, is exterior but I will be ripping all the sheetrock off all along this wall anyway (remodel) so I thought what the heck, I'll grab a sawzall and replace a few of the wood studs with metal at the same time, and attach concrete backerboard directly to the new metal studs in that section. I talked to the dealer that sold me the stove today, and he did say that the installation I described would qualify for the reduced clearance to 6", even with the insulation in there, hmmm....

However, I think it would be easier on the exterior wall to just add a 1" airgap as you all described, rather than replace the studs. So thanks B.G. for that link on how to do this!

And M.C. looking forward to hearing how that inspection goes.

 

[BXTF]

Kat,
Sorry it took so long but I had to wait for the building inspector to do his inspection. The stove is in and the inspection was fine
The non combustible wall with the one inch gap gave me the six inch clearance with no problem. I built the wall and my dealer did a great job on the installation. I'm still trying figure out why the 54 inch corner board through, the dealer called Jotul tec support and that's what Jotul wanted for the F400. I asked the building inspector the same question and he started measuring and he came up with 19 inches more then I needed, the same number I came up with. ( yes extra is better) Can you please let me know your choice on the hearth board size when you do your install.

So now the real fun starts, BREAK IN BURNS

 

[fjordrr]

Hey, I've been wondering how your inspection went - thanks for posting back, & congratulations for passing Did you run your walls with Durock out to 54" too, same as the hearth pad?

I've been wrestling with this dimension problem. Right now I'm almost set to install 44" of Durock on each wall of the corner installation.

re: pad - I was going to go with 44" with the first (raised) level, then drop down to floor level with another 10-12". So my pad will end up being about the same as yours. I did lay out the dimensions of the stove on the floor with tape last night, and 44" seems like it will barely clear the ash pan lip, so I am still pondering this.

Burn in time for you - I'm jealous! I'm still probably minimum 6-8 weeks out, the installers in my area are swamped right now

 

[BXTF]

Kat,
I put up durock 48 inches high and 36 inches wide for now, I can always add on. I wrote Jotul a letter asking them for their hearth requirements on a corner install. Once I get the final answer from Jotul I'll let you know. Temps in my area are in the high 30's tomorrow we start our first break in fire tomorrow .

There are some dealers in my area that still have stoves, with install dates this Month.
Chris

 

[fjordrr]

Good idea writing to Jotul, I thought of trying to call them yesterday but they don't seem to want direct contact with consumers, as either I'm blind or they don't have a phone # listed on their web site. Too bad their manual doesn't have better specs on the corner install hearth pad size.

BTW we did replace the studs in the exterior wall with metal, in the 44" section. Wasn't too difficult. Did have to relocate an electrical outlet (would have had to do that anyway) and use MC cable thru the metal studs for the electrical. I also managed to find non-combustible batts for insulation locally (McClendon's for anyone else in this area) - rock wool, 3.5" x 16 x 48, $4.69/ea.

So my next challenge is to figure out how to use metal studs to build a raised hearth - I'm thinking perhaps 10" high. And where the heck to buy Micore here, hmmm.....

 

[begreen]

Here's my take. For reference, I have a 54" corner pad. Measuring on the pad it looks like you'd be ok with the wall shield stopping at 44". At that point you should already be past the sides of the stove. I checked on our T6 which is a bigger stove and at the 44" point, the distance from the wall to the side of the T6 is 21.5" and it is right at the front corner of the stove.

To be absolutely sure, on the floor, tape out the 54" corner pad edges with a line of masking tape. Then make a cardboard template of the stove and set it where it will sit on the pad. Measure the front corner to the wall. Is the stove still within the 44"? If yes, the wall shield will completely shield the sides and you should be ok.

 

[fjordrr]

Thanks BeGreen for taking the time to measure your pad. I did lay out with template & tape where the stove should go, and it should stay within the 44" of Durock wall including the big ash lip, unless I've got something figured incorrectly.

Worst case scenario, when the installers come out later this month, if they don't like it, I'll just have to extend my Durock along the wall a bit. I'm not going to tile/rock until they give me the thumbs up.

Hey you wouldn't know who actually stocks Micore anywhere around Seattle, would you? I called the Redmond distributor ystdy but they're only open M-F.....

 

[begreen]

I don't know where to get micore easily in Seattle. You could ask at Home Depot or Lowes to see if they have mineral board insulation. But I suspect it may have to wait until Monday. Please let us know what you find for local suppliers. Here's a couple other places I'd call:

Cork Insulation Division
1943 1st Ave S
Seattle, WA 98134
(206) 622-1094

and maybe the Seattle office? http://www.soundisolationcompany.com/

 

[fjordrr]

Update on the Micore:

I did call the Redmond, WA distributor for Micore (Building Specialities) at 7:15am Monday morning. They did not have Micore 300 in stock, but their Portland warehouse did. They offered to have a 4x8 - 1/2" piece UPS'd up here as long as I was willing to have them cut it into 2x4 pieces for easy shipment & pay for the UPS. So I should be able to pick it up this afternoon in Redmond for a total cost of $44 for the one piece.

I'll be using this on both levels of the hearth pad (raised level did get framed out with metal studs ystdy & covered with 1/2" Durock). Lowe's in Issaquah is closing out their metal studs - last 10' ones I bought I paid less than a dollar apiece