Looking For More Answers - Antique Stove Install (CEMI)

[AmateurHour]

Hey Gang,
Short time listener, first time caller. I came across this board just recently when I ran into a unique problem - being given an old family heirloom, to the tune of a HEAVY Cemi free-standing wood stove made of 1/3" boiler plate. I've only seen photos of one other like it here on the forums, so needless to say info is exceptionally scarce on this cooker.

I've done LOTS of searching and reading on the forums and throughout the google-machine, found some great info and unfortunately still need some more. Maybe some of you can help.

As this beast (I'd estimate at around 700lbs) isn't UL Listed, I've used the NASD documentation sourced here from the Colorado Co-Op extension office for the basis of my specs.

Two questions to start:
1. I've removed the drywall, one wall is exterior and one is interior, and replaced the drywall with DUROCK (If I don't type it in capital letters each time my keyboard auto-corrects it to something else, so sorry in advance lol) onto the studs. I'll be putting up some stone veneer from the big orange store with thin set up the 9 foot wall. Is this enough to be considered non-combustable now, so that I can get my stove within 12-16" at the absolute closest to these walls? I'm trying for more but we're in tight quarters on this here ship.

2. I'm in the midst of building a hearth for the stove, over a hardwood floor on pier and beam construction. I anticipated I'd build it out of 2x6 framing, with 3/4" OSB on top of that and then a sheet of DUROCK over the entire thing before covering it with 12x24 slate tiles from that favorite orange store mentioned earlier. Since the stove isn't listed, I can't find an average 'r' value I should be seeking for the hearth build. Based on quick math, I'm coming up with a 'r'=1.61 value with just that material mentioned above. If I were to consider the at least 3.5" air gap under the framing and its associated 'r' value as well, I come up with 'r'=2.62. Is that sufficient? Needless to say, I can't find any Micore 300 otherwise this wouldn't be a topic of discussion for me. with concerns over the floor construction, I want to avoid a ton of extra weight if I can, therefore avoiding stacking more DUROCK (since I'm already calculating a total load here of about 1434 lbs roughly).

I'm sure I'll have plenty more questions but I'm trying to research everything I can before asking duplicate questions on things and upsetting the apple cart here with needless posts. That being said, if you think I haven't considered something please let me know - I'd rather feel stupid for not figuring it out while I'm building it and can change something than feel even more stupid for not figuring it out with the fire department battling a structure fire at my address.

I've had wood stoves in the past, even installed one in a new-construction format a few years ago in a previous house but that was A) new construction and B) a brand new stove that actually had directions, so the game was a bit different then.

Thanks in advance for the help - this place has been a great resource.

 

[bholler]

I've removed the drywall, one wall is exterior and one is interior, and replaced the drywall with DUROCK (If I don't type it in capital letters each time my keyboard auto-corrects it to something else, so sorry in advance lol) onto the studs. I'll be putting up some stone veneer from the big orange store with thin set up the 9 foot wall. Is this enough to be considered non-combustable now, so that I can get my stove within 12-16" at the absolute closest to these walls? I'm trying for more but we're in tight quarters on this here ship.

No that doesn't reduce your clearances to the studs at all. The cement board would need to be spaced off the wall atleast an inch with a gap top and bottom to get you down to 12".

 

[bholler]

2. I'm in the midst of building a hearth for the stove, over a hardwood floor on pier and beam construction. I anticipated I'd build it out of 2x6 framing, with 3/4" OSB on top of that and then a sheet of DUROCK over the entire thing before covering it with 12x24 slate tiles from that favorite orange store mentioned earlier. Since the stove isn't listed, I can't find an average 'r' value I should be seeking for the hearth build. Based on quick math, I'm coming up with a 'r'=1.61 value with just that material mentioned above. If I were to consider the at least 3.5" air gap under the framing and its associated 'r' value as well, I come up with 'r'=2.62. Is that sufficient? Needless to say, I can't find any Micore 300 otherwise this wouldn't be a topic of discussion for me. with concerns over the floor construction, I want to avoid a ton of extra weight if I can, therefore avoiding stacking more DUROCK (since I'm already calculating a total load here of about 1434 lbs roughly).

An air gap under the framing won't do anything. You would need an air gap above the framing. I usually do 4 layers of 1/2" cement board for unlisted stoves. I don't remember the r value off hand though

 

[AmateurHour]

No that doesn't reduce your clearances to the studs at all. The cement board would need to be spaced off the wall atleast an inch with a gap top and bottom to get you down to 12".

I somewhat arrived at that conclusion (reluctantly) myself. At least Im not *totally* crazy I guess.

So that being said, I'm building a mantle at 60" above floor height, roughly 54" above hearth height.

Could I then instead space another layer of DUROCK, 1" off the wall, with appropriate inlet/outlet air channels at bottom and top respectively, on the wall space between the hearth and the mantle to achieve my clearance requirements?

Thanks a ton for the help!

 

[AmateurHour]

An air gap under the framing won't do anything. You would need an air gap above the framing. I usually do 4 layers of 1/2" cement board for unlisted stoves. I don't remember the r value off hand though

It seemed crazy that it would do something, but hey, I'm just a simple guy getting myself into trouble with the google machine here. Glad you could clear that up.

I'd love to go with some Micore 300 in addition to my existing building materials, but with it being unavailable that isn't an option. I guess my next question would be, I'm going through all this trouble to achieve some arbitrary 'r' value which I don't even know is sufficient/insufficient anyway. Is there a basic target 'r' I should be seeking?

With some quick math at .39 'r' per sheet of 1/2" DUROCK, I come up with 1.56 'r' throwing down 4 sheets.

As I mentioned, with total weight and floor load being a consideration for me, I'm trying to make sure I do what I can to not overstress the floor joists and cause a structural problem (I live on a hill, so I have visions of my house sliding down and into the pond when the floor collapses).

Attached is a quick workup I did last night, trying to keep some numbers straight and see what makes sense of what. any opinion on it?

 

[bholler]

Look at NFPA 211 requirements for unlisted stoves that is what you should be following