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djrwolfe
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# Posted: 18 Jun 2021 12:14am
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New to the forum--I tried finding this answer, sorry if it's somewhere already discussed that I didn't see.
We recently purchased an off grid cabin (northern MN) that used lava rock as a heat shield behind the wood stove. Not only was it HORRIBLY ugly, but there was no air space behind the rock which means it was totally ineffective.
We've torn it all out, replaced the degrading insulation with Rockwool and a new vapor barrier, and plan to cover it with a layer of dry wall, then a 1" air gap, then 1/2" cement board covered with ceramic tile.
I have a few questions I'd love some advice on:
--I'd love to just use cement board scraps sandwiched together as an inexpensive spacer, but what type of screw do I use? Cement board screws max out at 2 1/4", and I'd need them to be MINIMUM of 3" (1/2" cement board, 1" space, 1/2" drywall, plus at least 1" of bite into the stud). I've read that cement board can cause corrosion if you don't choose the correct screw--would any stainless screw be sufficient?
--I'm not thrilled about the idea of leaving an air gap at the bottom/sides/top of the tiled heat shield, as it is difficult to finish nicely and seems like a trap for gunk and critters. I've seen this look nice for metal heat shields--but is it necessary for tiled shields?
(and yes, I've double and triple checked all the necessary clearances to combustibles for my particular stove as well as my insurance company!!)
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Brettny
Member
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# Posted: 18 Jun 2021 06:03am
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I dont believe you need an air gap behind a ceramic stove surround. As if it's far enough away it's not a heat shield. You would be following the spec for a clearance to a non combustible if you had tile behind.
Also if you do want the air gap you will need more than 1in of screw holding on what could be hundreds of pounds of ceramic tile, mastic and cement board.
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Steve_S
Member
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# Posted: 18 Jun 2021 06:30am
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Instead of using Cement Fireboard, switch to Magnesium Oxide Board (Mag-O) which is lighter, 1/2 the price, water & fireproof and is also an excellent tile backer. I should add, non-toxic and no offgasses of any kind. Cut it with a circular and cheap blade (wear a mask, dust = nasty) and use regular coated screws.
In my build, I used it behind my wood stove over the Drywall. I screwed the sheet through the drywall into the stud BUT left the upper 1-1/2" without screws.
I then used 1" long, 1/2" copper pipe couplings as an offset and attached galvanized steel so that it is 1" off of the Mag-O board. I used Stainless Screws & Washers to prevent discoloration or staining. The tin is also 1" OFF the floor surface (I have a concrete floor with ceramic under the woodstove area)
To "CAP" around the tin, I had my tin guy fold me up two 8' long U-Channels which is 2" x2" X1" with folded over edge for the front side (no sharps). I folded the the "cap" 45 degrees at 4' and then slipped the long edge behind the outside edges of the Mag-O Board and pushed it down but NOT tight against the Tin but with about a 1/4" front the edge of the tin so the air can come out. I attached the cap with longer stainless screws, through the tin ribs, the Mag-O through the back part of the tin and into the drywall.
It's a nice finish and Kid Safe as there are no sharps to get cuts. See attached photo's (I uploaded as 1024 JPG) to be conservative.
BTW: The airgap at top & bottom is a must, it has to allow air to flow up & out from behind it, The 1" off the floor is no problem but you do need at least 1/4-1/2" between the top edge of the tin & the bottom inside of the cap to allow the air to come out.
Hope it helps, Good Luck.
Steve
heatshield
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cap-end detail
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CAP U Channel
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ICC
Member
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# Posted: 18 Jun 2021 08:57am
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As Steve said an air gap is necessary if this wall panel is not spaced out to the larger clearance distances when there are no air gap panels. Air must be able to enter at bottom and exit at top. There are ceramic spacers available. S/S screws. the screws will only secure the ceramic panel spacing from the wall. You will need a some "legs" to carry the weight to the floor and a structure to distribute the weight.
I like metal panels. If you have a metal roof use the same color. Or something else complimentary to the decor. Copper if you have deep pockets.
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CabinBuilder
Admin
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# Posted: 23 Jun 2021 10:26am
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Some info here:
https://www.small-cabin.com/small-cabin-off-grid-heating.html
https://www.small-cabin.com/small-cabin-off-grid-3-wood-stove-safety.html
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snobdds
Member
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# Posted: 23 Jun 2021 01:33pm
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I had a metal heat shield made to go around the stove, instead of building out the wall around the stove. It still gets me to code.
So much simpler.
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Brettny
Member
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# Posted: 24 Jun 2021 06:05am
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I did the same in my full time home. Heat shield on the stove. I have drywall behind the stove with nothing special on it.
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