Safely Putting a Stove Closer than The Minimum Spec for a Alcove Ceiling That's Angled, Or Non-Comb

[Renovation]

Howdy!

I have conflicting constraints in my stove alcove design, and if I put the stove at my preferred height, it will be closer than the manufacturer's specification for minimum distance to an alcove ceiling.

Now the alcove's ceiling is angled up at a 45 degree angle for natural convection circulation, so the stove only violates the spec at its rear edge. More significantly, common sense tells me the angled ceiling will trap less heat and circulate more air than a flat one (that's why I'm doing it).

But yeah, who can say how much better, what's safe, etc? BeGreen can just reply with "no", and I'll forget that idea. I fully expect that trial balloon to be shot down, but I'm floating it out there anyway.

A more promising route--does anyone have an idea/reference/etc. for a non-combustible ceiling design? The ceiling is over a 3' by 10' alcove, tilted at 45 degrees. It bears no weight except for itself, insulation, shingles, snow, and maybe me. How about metal studs covered on both sides with some sort of non-combustible sheet rock (cement board?), with fiberglass or some other non-combustible insulation behind?

On a related note, is plain (unbacked) fiberglass insulation fireproof? I know it shouldn't touch a Class A chimney pipe, but that's to protect the pipe from hot spots, right?

I'm just geeking out here. It would be nice to have the stove at the height I want, but I won't do it unless I can do it safely.

Thanks, and stay toasty.

 

[Renovation]

PS I'd like to raise the stove about 7".

 

[Renovation]

Anyone? Anyone? :gulp: lol

Fair enough, it wasn't a very interesting or general question.

I'll put my own solution here, in hopes of helping someone who searches for it

First, some search terms: fireproof, ceiling, noncombustible... that should do it.

Okay, I figured out all on my own that I shouldn't violate the minimum clearance to a combustible ceiling, and researched options for a fireproof ceiling. That's a bit more challenging than walls, since its harder to build a stone ceiling.

Anyway, after a bit of research and pondering, my current design is cement board screwed to metal studs, backed by about a foot of unfaced (no paper or foil backing) fiberglass insulation. The unfaced part is important, because even foil backing can be flammable.

I'm going to attach a corrugated galvanized metal shield to the front of the cement board with 1" spacers. A spaced shield like this is usually used to protect a flammable surface and allow reduced clearances, but in this case it's for looks and to help convert energy from radiant to convection.

I'm thinking a blowtorch wouldn't faze this setup. Comments, corrections, and suggestions are welcome.

Stay toasty!

 

[johnstra]

I hope you document your build with lots of pictures. Sounds safe, being non-combustible. With all the effort your putting into this, spend some time on dimensional aesthetics. There are some standard proportions that just look good. From your description, you're going to have a lot going on in your alcove, so proper proportions will be essential to it looking nice. Have you decided on a stove? BK?

 

[nate379]

Information would be helpful.

What stove?

What is the height of the ceiling?

Normal insulation like Pink Panther will melt if you get it hot enough. To go around pipe there is a special insulation to use. It's $$$, but I can't remember the name.

 

[Renovation]

I hope you document your build with lots of pictures. Sounds safe, being non-combustible. With all the effort your putting into this, spend some time on dimensional aesthetics. There are some standard proportions that just look good. From your description, you're going to have a lot going on in your alcove, so proper proportions will be essential to it looking nice. Have you decided on a stove? BK?

Hey John,

Thanks for your interest and your thoughts.

Yes, I will take pictures and post them. It's the least I can do==if just as a cautionary tale--though construction won't start until Spring. I'm in AZ until then, and planning next year's work. I'd like to post my design at some point. I just fooled around with my free CAD program, and figured out how to make a .pdf, but not a jpg. The pdf is quite legible, so maybe I'll try to share that somehow.

I haven't decided on a stove, and won't for sure until I actually buy it, but right now the BK King is my bogey. But I'll keep trying to learn until then, and an eye out for new developments. Yes Woodstock, I'm looking at you!

Your message got me looking up golden rectangles and mentally dividing spaces into thirds. I'm by no means an expert at aesthetics, though I do have strong preference for simple, clean design and honest materials. I'll take your advice and keep my eye on proportion while I balance my technical priorities.

My process involves learning options and techniques, and incorporating them into my design, and discarding or de-emphasizing many of them--trying to learn each time. You'll see an example of that in my next message, lol.

I smiled when you said "a lot going on" because its true, but at the same time I believe great solutions don't call attention to themselves, they just work. Okay, enough rambling. Thanks again for your thoughts--have a great one.

 

[Renovation]

Information would be helpful.

What stove?

What is the height of the ceiling?

Normal insulation like Pink Panther will melt if you get it hot enough. To go around pipe there is a special insulation to use. It's $$$, but I can't remember the name.

Hey Nate,

Thanks for the insulation tip. I wonder what the melting temp is? I can't imagine I'd reach it, though the point may be moot.

My current choice, subject to change is the BK King Classic, unshielded, no fan. Their specification is 49" clearance to a combustible alcove ceiling, and I've read that sheet metal shield on 1" non-combustible spacers would reduce that by 50% to 25". I wanted to raise the Classic 14" for easy viewing and loading, which would put it even closer to the ceiling than 25"--hence the noncombustible ceiling.

It would be a effort to construct, and have some risk of unintended consequences, but I was fine was that as long as I thought it would offer the best overall solution. But then I realized that the higher a stove is raised, the less natural convective mixing it does with the room air--as an extreme, if the stove were at the ceiling, most of the warm air would stay up there. So, as of this moment I am leaning away from that, and towards putting the stove closer to the floor and with 25" minimum clearance, at the rear edge where the 45 degree ceiling passes closest. I feel pretty safe with that, because only one edge is that close, and a 45 degree ceiling has to stay a lot cooler than a flat one. Does that sound right?

Anyway, that's where I stand right now. As all the good men and women on this forum know, the fun is in the process, so I'm in no rush and am having fun. Thanks for your Princess reports--I hope you continue to have good luck.

 

[Renovation]

Normal insulation like Pink Panther will melt if you get it hot enough.

For what it's worth, from wikipedia:

The basis of textile-grade glass fibers is silica, SiO2. In its pure form it exists as a polymer, (SiO2)n. It has no true melting point but softens at 2,000 °C (3,630 °F), where it starts to degrade.

 

[begreen]

Two words, yes & overkill.

 

[Renovation]

Two words, yes & overkill.

Well, I suppose overkill is better than underkill, though nokill is best.

What do you mean by "yes"? You'd feel comfortable being under the minimum clearance to an alcove ceiling, if the ceiling is angled 45 degrees?

I'm glad you survived the storm.

 

[LLigetfa]

In my former home I had an alcove install under a flight of stairs. It too was below minimum clearance on one side of the stove but well above minimum at the centre by the flue. To appease the fire marshal, I installed a cement board with air gap spacers.

 

[Dakotas Dad]

I built a non combustible ceiling in my not an alcove.. I used steel 2x's and wonderboard. pictures in my link.

 

[Renovation]

I built a non combustible ceiling in my not an alcove.. I used steel 2x's and wonderboard. pictures in my link.

Aww, super-sweet photos, DD!

Thanks, extremely helpful--I hope to document my install half as well.

 

[begreen]

I just said yes to get a rise out of you. The metal cladding and insulation are the overkill part, though the metal will self-ventilate and could look cool in the right setting. Hold off on the insulation. You need the primary shield to be ventilated at top and bottom so that air can convect easily behind it.

About the stove... At first I was thinking Fireview for some reason. With the BK Classic, I am wondering if I have the full picture. This is a 30" stove going in a 36"wide by 120" tall space? The stove is 30" wide, so that sounds like a total red flag right away. This is more like a closet than an alcove. . . The math doesn't make sense. Maybe it's the lack of sleep. What am I missing here?

 

[Renovation]

I just said yes to get a rise out of you.

Ah, good job--I deserve so much worse. I've been told "gullible" isn't in the dictionary.

The metal cladding and insulation are the overkill part, though the metal will self-ventilate and could look cool in the right setting. Hold off on the insulation. You need the primary shield to be ventilated at top and bottom so that air can convect easily behind it.

Thanks and understood. Clearly I was unclear, since both you and a guy who was nice enough to PM me thought I was talking about insulating the air gap. No, I meant corrugated metal shield, then airgap, then cement board over the metal studs, and *then* insulation behind the cement board. I agree that the shielding could look cool. I've seen that galvanized corrugated metal used as a wall covering, and it looks surprisingly good, and compliments natural wood.

About the stove... At first I was thinking Fireview for some reason. With the BK Classic, I am wondering if I have the full picture. This is a 30" stove going in a 36"wide by 120" tall space? The stove is 30" wide, so that sounds like a total red flag right away. This is more like a closet than an alcove. . . The math doesn't make sense. Maybe it's the lack of sleep. What am I missing here?

It's amazing how hard it is to be clear, as hard as I try (I edit these messages a ridiculous amount before I send them). The alcove is 3' *deep* by 10' *wide*, by 7'2" high, with a ceiling at a 45 degree angle from 4' high on the back of the alcove to 7" high at its entrance. Better, yes?

Yes, you're right, sometimes I do think about overkill--I think it's part of my learning process. In the end I hope to come up with something good, as I learn and benefit from all the great help and information here.

As I said, now that I think keeping the stove low for natural convection is a consideration, I'm planning on only raising the stove 7" off the floor. BK's clearance spec to a combustible alcove ceiling is 49", so even if I set the Classic on the floor, its rear edge would be 32" from the slanted ceiling, requiring a shield. From what I've read, the metal shield on 1" spacers for a 1" air gap before a cement board wall covering over flammable wood studs reduces the clearance requirement by 50%, to 25". So, since I'll have to shield the ceiling anyway, I'll raise the stove 7" for the minimum shielded clearance of 25" and call it good.

As I asked before, does that seem pretty safe, since a slanted ceiling would have much better circulation than a flat one? Also, the alcove is 10' wide, (to provide wood storage out of the combustible zone), so I figure that helps circulation and cooling too. Reasonable?

Thanks, and I hope you catch up on your sleep! Glad you made it through the storm.

 

[begreen]

Thanks, took a nap, now it makes a lot more sense. It sounds theoretically possible, though 25" is very close to the stove top. I would contact BK and ask for their blessing for the clearance reduction. If they say yes, ask for it in writing.

For a clarification. The wall shield doesn't care what is behind it. In the case described, the cement board is superfluous as long as the ventilated metal shield is on non-combustible 1" spacers. However, there is no harm in adding the cement board. It just doesn't count in the clearance reduction requirements.

 

[Renovation]

It sounds theoretically possible, though 25" is very close to the stove top. I would contact BK and ask for their blessing for the clearance reduction. If they say yes, ask for it in writing.

For a clarification. The wall shield doesn't care what is behind it. In the case described, the cement board is superfluous as long as the ventilated metal shield is on non-combustible 1" spacers. However, there is no harm in adding the cement board. It just doesn't count in the clearance reduction requirements.

Given your concern, I'll just go with the non-combustible ceiling (cement board over metal studs), and be on the safe side. Then the spaced corrugated metal facing will have nothing to do with code, but will offer an extra layer of safety, look good, and help convect the heat. Easy peasy, ham and cheesy.

Thanks for your help. I have to go--some friends are going to show me how to catch snipe. I get to hold the bag!

 

[begreen]

I didn't see anything in Blaze King's alcove specs about a special qualification for a "non-combustible" ceiling. I haven't seen a spec, but it would seem that putting a non-combustible barrier in front of a traditional wood framed ceiling is not non-combustible, but rather a fire barrier. If this barrier is correctly ventilated top and bottom, it becomes a proper NFPA 211 wall shield, which -may- qualify for a distance reduction - if- Blaze King agrees. Call them.

 

[Renovation]

I didn't see anything in Blaze King's alcove specs about a special qualification for a "non-combustible" ceiling. I haven't seen a spec, but it would seem that putting a non-combustible barrier in front of a traditional wood framed ceiling is not non-combustible, but rather a fire barrier. If this barrier is correctly ventilated top and bottom, it becomes a proper NFPA 211 wall shield, which -may- qualify for a distance reduction - if- Blaze King agrees. Call them.

I'm not talking about that. I'm talking about putting a non-combustible barrier in front of a non-combustible metal-framed ceiling.

Back to basics, I'm already meeting clearance specs to a shielded combustible ceiling. I checked again, and NFPA and BK say a 49" clearance to an unshielded combustible ceiling is sufficient, and item (e) on this site's own chart:

https://www.hearth.com/econtent/index.php/wiki/NFPA_Wall_Clearance_Reductions/

says a spaced metal ceiling shield reduces that clearance by 50%, and shows a minimum clearance of 18" under those conditions--no ifs, maybes, or call the manufacturer. I'm at 25" so I don't understand what your concern is?

Additionally, I'm going the extra yard by making the shielded ceiling non-combustible.

That seems overly cautious to me, if anything. Please forgive me for pushing the point here, but I'm reluctant to bother BK about this, because I can imagine a manufacturer refusing to authorize something that isn't specifically in their manual--safe or not, within code or not--for liability reasons.

Please accept my apology for my persistence and for taking your time--I appreciate the time everyone gives so generously, and the chance to test and challenge my thinking--it's very helpful.