Vertical Air Gap?

[Squirrel1410]

Hi everyone,

I posted this design plan rescently with some clearance questions for the stove pipe, and got some great answers. Thank You!

I'm just wondering, if I use 1/2" Micore 300 and 1/2" cement board under the natural cut stone veneer, Is the 1" ventilated air space necessary? Or required? (I'm in MA if that makes a difference).

Stove is a Morso Squirrel 1410 and has rear heat shield.

Does the vented air gap just apply to older stoves?

I can definitely build one, but I don't want to! It's going to put a 1" slit in my mantle, and I'll have an ugly 1" opening along the bottom. It will also create some challenging stone work below the chimney opening, since the vent will need to exhaust there too. I would also need to use 1" spacers between the Micore 300 and cement board, and I'm not sure if they would dig into the Micore over time. Is the Micore strong enough to hold the cement board away using 1/2 by 1" aluminum spacers if say, a child runs full speed into the veneer wall? Could happen I guess...

Anyway, just wondering if there's any way to fasten these layers together without the air space and all it's potential issues and design challenges.

And another thing - if dust accumulates over time in a ventilated air space... isn't that a fire hazzard?

So many questions - I appreciate the info!

Rob

 

[begreen]

Might work, but there is no way we would know as this would be an untested configuration.

 

[Squirrel1410]

Well I guess I'll build it with the air space then, because I can't put this much time and money into something that the inspector tells me I can't use and have to rip down...

I'll screw Micore 300 to the wall, use 1" ceramic spacers between that and cement board, and put the veneer over the cement board.

 

[begreen]

There is no need for the micore at all in this case. The ventilated air gap is what offers the protection.

 

[Squirrel1410]

All the better then, my shield won't bump out from the wall as much. 1/2" cement board + stone veneer spaced 1" from the wall, vented.

The drywall behind is type X 5/8" fire rated anyway.

 

[kennyp2339]

All the better then, my shield won't bump out from the wall as much. 1/2" cement board + stone veneer spaced 1" from the wall, vented.

The drywall behind is type X 5/8" fire rated anyway.

Sounds like your good to go, just remember to leave a space a the bottom and top so air vent out between the dry wall and the back side of the cement board

 

[Squirrel1410]

Thanks, I plan to, except at the very edges, and a at the slope to the central raised part, just to take some weight of the wall off the spacers. I don't think that will slow the air flow any.

I think I can leave the wood mantle part un-vented since it's off to the side. But at least that can be altered if home inspector has an issue with it.

Got the Durock last night, shin stone veneer arriving Friday, and already have Micore.

Now to bust out the router and try to cut straight lines in my floor!

 

[begreen]

For 1"spacers you can use doubled-up, long strips of 1/2" Durock on each stud. That will provide furring strip spacerss to mount the heat shield cement board onto. Screw every 8" and don't worry about the weight. It will be very solid and strong enough to support the veneer.

 

[bholler]

The drywall behind is type X 5/8" fire rated anyway.

Fire rated drywall still has flammable paper on it and the gypsum will crumble once that paper burns. It is only meant to slow a fire down to allow time to escape.

 

[Squirrel1410]

Fire rated drywall still has flammable paper on it and the gypsum will crumble once that paper burns. It is only meant to slow a fire down to allow time to escape.

Yeah and it's painted - I wouldn't use the type X AS the heat shield by any means, it's just what the wall behind it has on it.

 

[bholler]

Yeah and it's painted - I wouldn't use the type X AS the heat shield by any means, it's just what the wall behind it has on it.

ok just wanted to be clear many people think if it says fire rated it is non combustible which is far from the truth. That and fire foam drive me nuts people use fire stop foam all the time thinking it is noncombustible and it is not it is extremely flammable. I was not saying you were doing anything wrong just wanted to make that point clear to anyone else.

 

[Squirrel1410]

ok just wanted to be clear many people think if it says fire rated it is non combustible which is far from the truth. That and fire foam drive me nuts people use fire stop foam all the time thinking it is noncombustible and it is not it is extremely flammable. I was not saying you were doing anything wrong just wanted to make that point clear to anyone else.

I could see that happening! I remember cutting it and thinking "how is this stuff any different than the other drywall?" they should have coated it with something noncombustable.

 

[bholler]

I could see that happening! I remember cutting it and thinking "how is this stuff any different than the other drywall?" they should have coated it with something noncombustable.

Even if it were coated with noncombustible the gypsum would still break down at temp. As it is it serves its purpose in that it delays the spread of fire. They should just be more clear with the labeling

 

[Squirrel1410]

It has begun. Living room's trashed. My poor wife... lol

 

[kennyp2339]

It has begun. Living room's trashed. My poor wife... lol

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