material for inside chase of gas fireplace

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Moe951

New Member
Apr 16, 2020
2
Asbury Park, NJ
I am seeking advise on what material to line the inside of the chase pictured in the photo below. I have a stack of 1/4" Hardibacker on site, but started thinking I should be applying Durock 1/4 instead. If either of these materials are appropriate, should there be a free air space established between the framing and the Durock? Something tells me a saw this requirement 30 years ago when I installed my woodstove in an area where the walls were stick framed. I would seal the seams with the fireproof caulk to make sure the inspector was happy, unless someone could suggest a better way. Also, the concentric pipe will travel up approx. 17 feet before it exits the roof. Do I have to frame for some sort of fireblock at the 8 or 10 ' level? I provisioned for the 3"x48" vent up top as seen in the pic, and the "false ceiling" up there as well. Am I missing any detail? Fireplace will be 40k unit, max.
chase_!.png
 
Also,
What do I need to transition through the roof, including insulation requirements. How close should the spray foam guy go to where the vent goes out the roof? As you can see in the pic of previous post, its very busy with framing....I may have to remove or cut one of the short blocks up there to route the chimney out. I'm assuming there are concentric 45's to twist away from the centered roof ridge LVLs. Thanks again.
 
You will have to decide on what model you want, before you can determine
what the requirements are. Generally speaking, you can use 1/2" sheetrock
inside the chase, but each manufacturer subjects its units to different testing
parameters. The install manual for every unit specifies the requirements for the
direct venting components & venting configurations.