Fireplace Surround Non-Combustible Materials Use

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stufrus

New Member
Mar 14, 2020
4
Virginia
I am trying to finish off my 1980's fireplace that was never completed when the home was built. I need to apply a combination of drywall patching and a non-combustible material. The drywall patching is needed to narrow the current drywall cut outs on the red brick so that I have a wider selection of GFRC hollow pre-cast mantels, and the non-combustible materials, ie, Durarock, Micore, Wonderboard, Hardieboard..etc. is needed to both fill in the difference in depth from the red brick facing and the drywall that now exists around the fireplace wall.
On the left side red brick face, I plan on using a 16" x 32" concrete type board on the entire red brick face. Then, on this left side, use a piece of drywall, some 10" x 32 and patch and blend into the existing drywall. Then, use another piece of concrete type board, 6"x32" as the 6" set back for non-combustible materials.
On the right side, the fireplace wall behind the drywall was not plumb. At the top, there is about 1/2", the thickness of the drywall itself. But on the bottom, the distance from red brick to drywall is about 1". So, I need to use some kind of mortar, cement, refractory element and create some kind of tappering so that when I apply the drywall patch and the concrete type board, everything is flush, plumb and even. I'll end up with a 6" setback of a non-combustible material on this right side.
The header above the firebox has not yet been cut out. But will have a 6" setback above the firebox of a non-combustible material.

QUESTIONS:

1) Which brand of non-combustible type of concrete board is best suited for creating this surround, that would meet code.

2) what kind of material, cement, refractory cement, thinset, mortar ...etc is best used for attaching the concrete board to the red brick.

3) on the right side red brick, where I need to create a tappering effect to plumb the red brick, what materials is best suited for this, so that a drywall patch and a cement type board will adhere to or be fastened over.

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