Freestanding Heat Shield Construction

[ironguy]

Hey Everyone. Man is this a great forum. I love being able to read about what everyone's doing and ask my own questions as well. Here's my latest question----I'm thinking of fabricating a steel heat shield to stand on the hearth pad behind my stove. For those of you who have such a shield, how thick is the steel it is made of? I've seen one commercially offered that is about 1/8" thick; I've seen another that is made from 14 gauge steel, roughly half as thick. In your estimation, how important is the thickness of the steel the shield is made of? I've got some nice big pieces of steel approximately 14 gauge; but I want to feel confident that it will be heavy enough to do its job with respect to the heat it is meant to deflect. Thanks in advance for any thoughts.
Andrew

 

[Heatsource]

the thickness of the steel doesn't matter much, its the air space it creates that is insulating the wall
22ga sheet metal should be fine

 

[Jags]

the thickness of the steel doesn't matter much, its the air space it creates that is insulating the wall
22ga sheet metal should be fine

Agreed. The only possible difference would be for a free standing unit, a little bit more rigid (thicker) material, might be easier dealt with. Possibly a bit more sturdy (if that even matters).

 

[fossil]

If the purpose of the shield that you're contemplating is to reduce the manufacturer's required clearance to combustibles, then there are a few other things that need to be discussed/taken into account. What is the stove? Is the stove already installed and operating? Rick

 

[ironguy]

The stove is older. It's an Aurora stove of unknown age; but it's in really nice shape. I know this isn't the correct forum for the stove---I didn't think we'd wind up discussing the stove itself. So, sorry about that. The stove is not hooked up yet; almost. And you are correct, I am looking for the heat shield to reduce clearances a little---but not much. The stove will sit facing out of a corner; the walls are filled with windows, so I can't put a heat shield on the wall. Otherwise I'd just do that. The clearance I'm looking to have is around 24"; nothing extravagant.

 

[Machria]

I would also think the thickness would be almost meaningless. It's the air space, and ability for that air to move around in it. If it will stand on it's own ("freestanding"), you should make sure to cutout holes in the bottom, so the entire shield does not sit on the floor. I would do something like cut out every 2" of it along the floor. Have a 2" open space (say 2" tall x 2" wide) followed by a 2" space sitting on the floor, then 2" x 2" cutout..... all the way across the bottom. This lets the air come in the bottom, go up and out the top, a natural convection which would keep the wall "insulated" from the heat.

 

[fossil]

Do you have the original manufacturer's clearance and hearth requirement information?

 

[fossil]

If the sides and the top are open, then ventilation need not be provided along the bottom edge. Won't hurt, but it's not required. Rick

 

[Jags]

If the sides and the top are open, then ventilation need not be provided along the bottom edge. Won't hurt, but it's not required. Rick

Rick, I do believe that some mfg (and I can't remember which ones) actually state that a heat shield needs the bottom notched. I wish I could remember what manual I saw that in, but I don't.

 

[Machria]

I've never seen a regulation for "free standing heat shield", if there are any? But most regulations for wall mounted heat shields require a 1" gap or more between the bottom of the heat shield and the floor, of course in addition to the 1" standoff gap between wall and sheild....

 

[ironguy]

No, I don't have any manufacturer's info on the stove. I've tried to find out those things, but no one seems to know. I posted a thread in the forum for older stoves, and I didn't really find much out.

The heat shield I'm wanting to do would be freestanding. Kind of like this one HERE. The walls in the corner behind the stove are filled with tall windows, so I can't put something on the wall; it would cover the windows.

 

[fossil]

Rick, I do believe that some mfg (and I can't remember which ones) actually state that a heat shield needs the bottom notched. I wish I could remember what manual I saw that in, but I don't.

NFPA 211 open in front of me, shipmate. If you want to close up/finish the sides, then the bottom must allow ventilation. If the sides are open, then venting from the bottom's not required. The top edge, of course must be left open in any case. Rick

 

[fossil]

Yeah, that'll work. In the absence of OEM info, you have to revert to NFPA 211. That means 36" clearance to combustibles all around. The metal shield you're talking about would buy you a 66% reduction of that clearance requirement...all the way down to 12". CTC is always measured from the closest point of the stove to the nearest combustible material, just as if your shield wasn't there. Hearth requirement is another question. What's the floor construction where this beast will dwell?

 

[Machria]

No, I don't have any manufacturer's info on the stove. I've tried to find out those things, but no one seems to know. I posted a thread in the forum for older stoves, and I didn't really find much out.

The heat shield I'm wanting to do would be freestanding. Kind of like this one HERE. The walls in the corner behind the stove are filled with tall windows, so I can't put something on the wall; it would cover the windows.

Buy that one!

 

[Jags]

NFPA 211 open in front of me, shipmate.

Good enough for me, shipmate.

 

[Machria]

CTC is always measured from the closest poijn of the stove to the nearest combustible material, just as if your shield wasn't there.

And the nearest combustible material includes the tile and/or durarock in front of the studs, correct? Even though the tile is not combustible, it's considered combustible since it's against the wood, is that correct?

 

[Danno77]

If it was mentioned then i didn't see it, but other than peace of mind a freestanding heat shield doesn't take place of your normal mounted heat shield. if it isn't part of the construction then it doesn't exist according to code. What I'm trying to say is that if this has to pass inspection then it has to pass without the free standing heat shield, even if you cross your heart, hope to die, promise to use it.

 

[ironguy]

I thought about buying that one! Only I've got some nice sized pieces of 14 gauge steel I can use to fabricate one pretty easily, I think. Provided that is thick enough, and it will be safe. I called a local fireplace supply place here today just to see what they might have in stock, and he didn't even know what I was talking about. Said he'd never even seen such a thing before, and asked me if I had! I was like, Wow. I didn't know these items were that uncommon; I couldn't believe he'd never seen one. Strange.

The floor is ceramic tile at the moment but is going to get remodeled. I want to build an actual raised hearth of some kind for the stove to sit on. I was thinking I'd tile it with slate perhaps.

 

[fossil]

And the nearest combustible material includes the tile and/or durarock in front of the studs, correct? Even though the tile is not combustible, it's considered combustible since it's against the wood, is that correct?

No, actually you get to "fudge" the thickness of that non-combustible material that's in direct contact with the combustible wall. The measurement is still from the stove to the combustible as though none of the non-combustibles were there. The tile or whatever applied directly to the drywall or whatever just doesn't buy you any clearance reduction unless it's substantial. For example, 3½" thick masonry (e.g. common brick laid flat) applied directly to the wall (no air space) buys a 33% reduction. There are other configurations specified in the NFPA 211 table, as well. Rick

 

[fossil]

Shield: 24 gauge is minimum.

Floor: What's underneath the ceramic tile?

 

[ironguy]

Maybe I should think about attaching the heat shield to the stove then; I didn't know it wouldn't count. The hole in the ceiling isn't going to move any farther from the wall; so I'll need to do something.

 

[ironguy]

Just subfloor is beneath the tile right now. They didn't use cement board. I have no intentions of relying on that tile for anything; I can't even stand looking at the stuff; can't wait until I get to tear it out. The stove definitely needs a hearth pad of some kind.

 

[Jags]

Maybe I should think about attaching the heat shield to the stove then;

Why not to the wall with spacers?

 

[ironguy]

I can't attach the shield to the wall because the wall is filled with windows.

 

[Jags]

Got it, forgot that part.