Building new brick hearth - rock wool behind the brick?

[BlueRidgeMark]

Hi, folks. I'm going to be doing some remodelerating of the house, which includes building a new brick hearth for my Fisher Grandpa Bear. This will be a floor-to-ceiling hearth, with a short side on an outside wall (standard 4" cavity0, and the longer side against a bedroom wall. The outside wall is stick frame, currently with poor quality, old fiberglass insulation. The bedroom wall will be new build. In the interests of fire safety, I plan to make the new wall of steel studs sheathed in fire-rated drywall.

I have been toying with leaving an air gap behind the rear wall, between the brick and the bedroom wall. OR possibly a gap filled with rock wool.

I have a few questions about this:

1. Is this even worth the bother? Will I gain any real fire safety, or should I just attach the brick to the drywall in a conventional manner?
2. With a gap, would the single thickness of brick be stable enough? Or does it need the support of that wall behind it?
3. What would you suggest for better fire safety, or is the brick plenty by itself?
4. What about the outside wall?

Thanks for your ideas!

 

[begreen]

Safety comes from proper clearances. Fire rated drywall gains no clearance reduction. Use cement board instead if a clearance reduction is desired. With no protection, the Grandpa will need 36" clearances, all directions. This can be reduce by 50% with a full brick wall and 66% with a ventilated, non-combustible wall shield. Here is a primer on the topic. There is a link to the NFPA clearance reduction chart in the middle of the article.

Wood Stoves and Fireplaces Thread 'WOOD STOVE WALL CLEARANCES - PRIMER'

Oct 18, 2015

Written by Ken Rajesky, Hearth Industry Expert.

After the difficult decision of what stove to buy has been made, you’ll need to install the stove safely. However good the stove is, it’s still not safe unless installed to manufacturers specifications.

First, review the owners guide that came with the stove. Discuss the installation with your retailer. If you have further questions, contact the technical service department of the manufacturer. The Hearth.com Forums (on this site) can also help you get answers about stove clearances.

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[BlueRidgeMark]

Hmmm. It's been running since the 70s with about 8" of clearance. There's a stone facing on the 2x4 outside wall, and I have no idea what's behind the stone.

If the rest of the construction in this house is any indication, I'm pretty sure it doesn't meet code!

 

[begreen]

Pyrolysis happens over time. It lowers the ignition point of wood. Sometimes this takes decades to show its ugly head.

 

[BlueRidgeMark]

Well, 50 years ought to be enough for it to show. But even with a lowered ignition point, it's pretty hard to ignite wood with only radiant heat through a stone wall.

But in any case, it won't be dealing with it much longer. The new location will have the stove about 3 feet or so from the outside wall, and the back wall will be brick over steel, so I don't think there will be much problem there.

 

[begreen]

This fire started due to pyrolysis in a friend's father's house after 35 yrs of wood burning. It nearly killed his sister.

But in any case, it won't be dealing with it much longer. The new location will have the stove about 3 feet or so from the outside wall, and the back wall will be brick over steel, so I don't think there will be much problem there.

Probably not, as long as the clearance requirements are met or exceeded.

 

[bholler]

Well, 50 years ought to be enough for it to show. But even with a lowered ignition point, it's pretty hard to ignite wood with only radiant heat through a stone wall.

But in any case, it won't be dealing with it much longer. The new location will have the stove about 3 feet or so from the outside wall, and the back wall will be brick over steel, so I don't think there will be much problem there.

Yes its hard. But it can happen especially if there is a chimney fire. Or if you space out and leave the air wide open for a load of wood getting temps much higher than normal. If you're doing steel studs, just insulate with rock wool cover it with cement board then the brick