Gas stove insert clearance to mantle

[Benjamin Thompson]

I have a question about a gas fireplace insert that is improperly installed. The manual calls for 23 inches from the top of the insert to the mantle. In gthis case, the mantle is drywall. The clearance is 9 inches. The mantle extends 3 inches over the insert.
Could the mantle be modified by installing a non combustible material like ceramic tile or does it need to be removed?
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[Mike Kleisch]

I’m thinking it needs to be removed. The instructions call out 23 inches, and say the shroud should not touch combustibles and it appears to do so. I’m guessing wood behind the sheetrock, which is not good, and sheetrock itself is not considered non-combustible, it is paper faced.

You would have to dig into the manual or call the manufacturer to see if there are any reduction methods allowed, or at least someone would have to check.

[Eric Barker]

If the insert is improperly installed then the mantle is irrelevant.

[Chris McIntyre]

It says shroud cannot touch combustibles, I don't know that I would consider drywall combustible but since the mantel is partially built over the shroud and there is no way to know for sure how it is built, I would say it needs to be removed. Also drawing shows 23" to the mantel, unless it says 23" to a combustible mantel it would still be wrong.

[Bob Harper]

Drywall is combustible

[Dave Mortensen]

Bob,
In my neck of the woods, the AHJ says drywall can be used as a thermal barrier:

"Thermal barriers are used to cover foam plastic. Requirements are found in IBC 2603.4. Exemptions from thermal
barrier requirements are found in IBC 2603.4.1. The following products are acceptable thermal barriers:
1. ½ inch Gypsum Wallboard, etc."

Just trying to ascertain the reasoning if the drywall is combustible, does it still give enough protection to be used as a "thermal barrier" just not a non-combustible material?

[Lou Curley]

"Thermal barrier" and "noncombustible" are 2 different things. Noncombustible materials pass ASTM E136, which drywall does not.


Bob,
In my neck of the woods, the AHJ says drywall can be used as a thermal barrier:

"Thermal barriers are used to cover foam plastic. Requirements are found in IBC 2603.4. Exemptions from thermal
barrier requirements are found in IBC 2603.4.1. The following products are acceptable thermal barriers:
1. ½ inch Gypsum Wallboard, etc."

Just trying to ascertain the reasoning if the drywall is combustible, does it still give enough protection to be used as a "thermal barrier" just not a non-combustible material?

[Benjamin Thompson]

I am exploring options for my client. He really likes the mantle and doesn't want raise it up another 14 inches.
What do you all think of this solution.
Remove all drywall at the mantle (bottom, front, sides and top) and install 1/2 inch hardie backer or similar and install ceramic tile bedded in thinset. There would still be combustible wood framing behind the tile and backer board.

[Billy Stephens]

restating what Chris posted.

The attachment says Shroud cannot touch combustibles.

The shown Clearance material is not specified but the Distance is at 23 inches.

Unless you have some other Manufactures Installation Instructions Nothing is Allow lower than 23 inches.

[Bob Harper]

I am exploring options for my client. He really likes the mantle and doesn't want raise it up another 14 inches.
What do you all think of this solution.
Remove all drywall at the mantle (bottom, front, sides and top) and install 1/2 inch hardie backer or similar and install ceramic tile bedded in thinset. There would still be combustible wood framing behind the tile and backer board.

The tile and cementitious backer board will absorb a lot of heat and conduct it to the combustibles. Generally, this is a fire hazard. However, check with the mfr. as sometimes they will state the requirement for "non-combustible" materials but actually allow non-comb. board over combustible framing. Still a bad practice. BTW, metal studs conduct a lot of heat, too.