Framing Around Fireplace Opening for Gas Insert (see pic)

Tom PultzJanuary 25, 2009

Attached is a picture of what's left of our wood burning masonry fireplace that we are converting to a gas insert. As you can see, the existing brick facing and raised hearth around the firebox have been removed and the hole in the floor where the hearth was has been patched.

I would like to frame around the masonry firebox opening up to the edge of the firebrick to account for the layer of brick that has been removed so when we get a mantel made it will be proud of the wall face as it was previously... then cover the framed in area with granite or marble.

Question: can I frame around the firebox (up to the existing side opening) with wood 2x4 studs as long as I cover them with fireproof cement board? I was going to use two layers of 1/2" board. Cement board and matching stone will also be installed on the floor.

The current width of the opening is about 36" and the insert inself is about 32" wide.

The installation instructions say the insert must be installed in a masonry fireplace or zero clearance unit. Is my plan OK or do I need to use metal studs in the area adjacent to the firebox opening.

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SeattlePioneer

Look in the installation manual for a section talking about clearances to combustible mantles. A combustible mantle is any combustible material sticking out over the top of the fireplace. There is often a diagram that illustrates how far a mantle can stick out at various heights above the top of the fireplace.

Commonly you get warm air that can be quite hot coming out the top grill of a gas fireplace, and that can be a fire hazard id the clearances described above aren't respected. That ESPECIALLY includes Christmas stockings and such, which must be set out with care to comply with the specifications of the fireplace manufacturer.

    Bookmark   January 26, 2009 at 12:30AM
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Tom Pultz

seattlepioneer: I'm well aware of the clearances to combustible materials as specified in the installation manual. That's not what I'm asking.

I want to build a framed wall if you will, that surrounds the outline of the fireplace opening (but lower in height). This framed "wall" would extend to the double wall studs on each side of the brick. The whole wall would be faced with cement board and then portions of it covered in tile, granite or marble, then a mantel installed over that. Basically, I just want to extend the firebox out into the room about the width of the brick that was removed when we demo'd the fireplace hearth and face.

    Bookmark   January 26, 2009 at 8:40PM
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ventupete

I wouldn't use wood studs even if you cover them with cement board. I've seen wood studs get charred even behind a course of brick and cement board! Use steel studs and two layers (at least on the side facing the firebox) of 1/2" cement board. The studs are pretty easy to work with and the cement board screws (Hardibacker makes square drive screws with a square driver in the package) will work well to attach to the steel studs. Why have to worry about it? Good luck, looks like a fun project.

    Bookmark   January 27, 2009 at 7:57PM
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