Attaching cement board to zero clearance insert wood fireplace

[Andrewz]

I have had an Astria Ladera wood fireplace installed. My wife has finally figured out what she wants so I can now close the wall up. My question is how to attach the USG Durock cement board where it overhangs the metal of the fireplace to then be able to tile on top. There is an overlap to the top and bottom just to where the tile lip is on the fireplace (highlighted in red). If the cement board is not fixed, when you press on it there is some give and flex which I am afraid will cause failure of the tile.

I am pretty sure this metal area it not important to the fireplace box so do I just use USG Durock self tapping screws for metal studs and screw into the fireplace? Leave it loose? Other? Really don't want to hit something important with the screws. If yes to the screws 1 row every 6-8''? USG says leave 3/8'' from edge and 2'' from corners.

We want to do a carrera marble subway tile . Any advice on best mortar to use for this purpose? USG says ''latex-fortified mortar or Type I organic adhesive ''

Thanks for your help!

 

[bholler]

I have had an Astria Ladera wood fireplace installed. My wife has finally figured out what she wants so I can now close the wall up. My question is how to attach the USG Durock cement board where it overhangs the metal of the fireplace to then be able to tile on top. There is an overlap to the top and bottom just to where the tile lip is on the fireplace (highlighted in red). If the cement board is not fixed, when you press on it there is some give and flex which I am afraid will cause failure of the tile.

I am pretty sure this metal area it not important to the fireplace box so do I just use USG Durock self tapping screws for metal studs and screw into the fireplace? Leave it loose? Other? Really don't want to hit something important with the screws. If yes to the screws 1 row every 6-8''? USG says leave 3/8'' from edge and 2'' from corners.

View attachment 248410

We want to do a carrera marble subway tile . Any advice on best mortar to use for this purpose? USG says ''latex-fortified mortar or Type I organic adhesive ''

Thanks for your help!

Read the instructions for the fireplace but I am pretty sure you can't cover any of the face

 

[Andrewz]

Read the instructions for the fireplace but I am pretty sure you can't cover any of the face

Thanks but I did read the instructions. Those areas CAN be covered which is why there is a built in ledger/tile lip. Simply has to be "non-combustable" material.

The issue is there is no info on how to attach said material. With expansion/contraction it would seem weird that they expect to mortar/mastic direct to metal. Other manufactures provide a metal lats kit. In the attached photo you can see the exact same fireplace with installed with these area's covered that I took from promotional material. Some references (for other fireplaces) say to just use metal screws to fix the Durock to the fireplace. Others have said it is a small area, just have a ridged spacer behind to avoid too much flex and just leave it loose.

Obviously a real installer would know but I would ideally like to do this myself.

 

[begreen]

As far as I can tell the rectangular metal box at the top front of the fireplace is a spacer and hollow. If so, screwing into it to secure the cement board should be ok. Verify this with Astria support. Just don't screw into the fireplace body below it.