Gas Insert - Building Out from firebox

[kal72]

I am replacing my old wood burning fireplace with a Regency gas insert. I have removed some of the old face brick from my fireplace and constructed a steel stud and cement board "frame and mantel" that extends approximately 5.5-6" inches out from the existing firebrick. With the steel and cement board, I believe I am ok with my clearances to combustibles (6" according to the manufacturer and local code) but am now concerned that my "built out" section may be an issue because the front 6" inches of the insert will extend out from the original firebox and I cannot find any guidance on what is allowed here except the usual use of steel/cement boards and sealing off, so heat is restricted from entering my new framed cavity.



As you can see from the pic, I have not attached the top stud,cripples and face cement board until I can add cement board to the portion above and seal off the cavity. On the bottom, the cement board only extends 4" past the firebrick (closer to 6" on the sides).

Question 1: Is there any limit to how far out of the firebox I build for an insert, or am I ok provided I use cement board and have my clearances to combustibles and properly seal.

Question 2: Since the top of my insert will be 10" below the bottom edge of the top firebrick, could I build an angled cement board deflector to direct hot air from the back edge of my top steel stud and the front 6" of the top of the insert back towards the interior of the firebox. See my cartoon representation of this (blue represents steel studs and cement board

 

[DAKSY]

Which Regency gas insert are you installing?

 

[kal72]

It’s a Horizon series HR14Re

 

[DAKSY]

Technically, your installation manual does not cover modifications to existing masonry built fire places. Your idea for an angled cement board deflector seems sound too me, but I am not certified to make that call. Your BEST bet would be to contact a local hearth shop that deals in Regency products & pick the brains of a Lead Installer. If they don't give you any assistance, then you will need to contact your local code enforcement official for certification that it is an acceptable install. Without their guidance, you may be SOL if your insurance company has to respond to a damage claim...