Framing around prefab fireplace box

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chew_baka9

New Member
Mar 19, 2018
4
New Jersey
Hi All,

I've been looking at these H-burners for a gas fireplace as part of a new construction project.
To use these H-burners, I understand that I need a real wood burning fireplace, then convert it. I'm thinking of using a prefab zero clearance box which requires the proper chimney flue for burning wood.

I need to immediately route the chimney flue back away from the front of the firebox with the specified elbows to then make the straight shot up to the roof. This leaves some extra space at about the 6 foot level between the fireplace front plane and the front of the flue pipe.

My question is about the framing for a wood burning prefab box (looking at Superior WCT series).
Since the chimney pipe is moving back away from the front in the space over the box, Can I frame up to the flue pipe over the firebox while maintaining the proper clearances with the flue pipe?

So this will look like a step over the box at about 6 foot level. Most framing I have seen goes straight up to the ceiling at the opening of the firebox. Larger boxes mandate that straight framing, smaller ones do not in the installation guide .

I want to make a larger mantle that fills the space between the front of the fireplace and the flue pipe at about eye level--- 6 feet high.

With a combustible 2x4 sitting right on the standoff on top of the firebox, I can't see how this might be a problem. The non-combustible cement mantle and cement board backer I am considering would be at least 25" away from the top of the fire box.

I know b-vents and direct vents are easier but thanks for your thoughts.

Regards.
 

DAKSY

Full Time RVer
Staff member
Dec 2, 2008
9,542
Wherever we're parked
As long as you maintain the clearances cited in both the ZC box manual & the instructions for the venting you will be good to go.
We installed a LOT of ZC boxes the were "proud" of the wall & offset the venting for exactly the same reason you want to do it.
Communication with the local Authority Having Jurisdiction (AHJ = Code Inspector), will confirm this.
 
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chew_baka9

New Member
Mar 19, 2018
4
New Jersey
As long as you maintain the clearances cited in both the ZC box manual & the instructions for the venting you will be good to go.
We installed a LOT of ZC boxes the were "proud" of the wall & offset the venting for exactly the same reason you want to do it.
Confirmation with the local Authority Having Jurisdiction (AHJ = Code Inspector), will confirm this.

******
Thanks for your reply. Will check it out with the inspector.
 

chew_baka9

New Member
Mar 19, 2018
4
New Jersey
A follow on question about the 8DM offset...

I need at least an 18 1/2" offset (from front edge, 12 1/4" from center of flue ) of the 8DM flue pipe as it rises away from firebox(proud from the wall) with a 30deg elbow.
What combination of elbow and straight pipe can give me that offset?
And what would the total rise be?

Looking at the charts, I am figuring

offset
4 3/8" elbow
9" straight 12" flue pipe.

13 3/8" total offset

16 3/8 + 25 3/4 = 42 1/8" total rise.


Clearance from the 8DM pipe for the firebox I am looking at, indicates 1" to combustibles.
Can local codes differ from the manufacturer's recommendation pushing clearances to 2"?

This is an installation in New Jersey.

Thanks for your response.