Clearances for non-combustible assembly

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oldhat

New Member
Sep 29, 2021
2
Guelph, ON
I'm considering installing an uncertified freestanding wood stove into an outbuilding (formerly a garage, but the garage door has been removed and it is no longer possible to get a vehicle inside) on my property here in Guelph, Ontario. The building is a single story CMU structure on a concrete slab with a stick-framed roof. The walls have no interior framing, insulation or wall covering - for now. I'd like to install the stove ASAP but leave myself the flexibility to frame, insulate and drywall the interior in the future.

Question #1 - when installing a wood stove on a concrete slab, near a CMU wall, are there any minimum clearances I need to observe? All clearance information on here seems to be regarding combustible materials. This suggests that there are no clearance concerns with non-combustible materials, but it doesn't seem to be clearly written anywhere.

Question #2 - when I finish the interior of the building I'm planning to build the wall behind the wood stove with steel studs, Rockwool Comfortbatt insulation and either Durock with a parged and painted finish, or some type of fire-resistant non-combustible drywall if I can find it (recommendations anyone?). This wall assembly will extend 4' on either side of the wood stove. If I understand correctly, this is a fully non-combustible wall assembly and shouldn't come with any minimum clearances either - do I have this right?

Apologies if this is a newb question but can't seem to find this explained anywhere else.

PS - planning to position the wood stove so that the back wall of the stove is approx 8" away from the face of the CMU wall. That way when the interior walls are built I'll have about 4" of space from the stove to the face of the wall for air circulation.
 
This is US code. I am not sure how closely Canadian code follows.

#1 - Correct, there are no combustibles so clearances are not an issue.
#2 - The stud wall behind the stove is not non-combustible if wood studs are used there. If metal studs are used then yes, it's entirely non-combustible. If wood studs are used and then covered with a non combustible material like cement board or sheet metal - on 1" spacers with a 1" gap at the bottom and top - then it qualifies as a shielded wall that can reduce the rear clearance from the wood studs to the stove down to 12". The 8" planned would not be permissible unless metal studs are used. Cover them with cement board which can be painted or covered with tile for a more finished look.
 
I've always wondered: drywall is not non-combustible (paper facing). How is paint (on cement board) non-combustible? Latex burns...
 
This is US code. I am not sure how closely Canadian code follows.

#1 - Correct, there are no combustibles so clearances are not an issue.
#2 - The stud wall behind the stove is not non-combustible if wood studs are used there. If metal studs are used then yes, it's entirely non-combustible. If wood studs are used and then covered with a non combustible material like cement board or sheet metal - on 1" spacers with a 1" gap at the bottom and top - then it qualifies as a shielded wall that can reduce the rear clearance from the wood studs to the stove down to 12". The 8" planned would not be permissible unless metal studs are used. Cover them with cement board which can be painted or covered with tile for a more finished look.
I'm planning to use steel studs for the 8' section of wall behind the stove so all good!