Mosaic Fireplace Surround

[LevelItUp]

I have a job where the designer would like to install a mesh backed polished marble around a fireplace. The mosaic has a few fairly thin tiles in it (1/4" x 1") and 1/8" grout lines. I have two concerns

1. With this sized grout line in between such small pieces, I have some concern of the grout breaking out due to different expansions. This is a gas insert and doesn't see much use, I'd just hate for an owner down the road to come along and use it all the time and have the grout fall out.

2. Has anyone heard of problems with the mesh backing charring, burning or discoloring when laid over the edge of these inserts? It will be in thinset, I just didn't know if it will burn out of it or how that would work.

[ScottinSoCal]

I can offer a single data point - my own gas fireplace. I made the surround using a mesh-backed slate and glass mosaic, and it's held up well for almost a decade. I used 1/2" durock for the backer and regular thinset to hold it on.

[prodjsaig]

I thought about the heat aspect on the wall and unless its directly exposed to the inside air of the fireplace (think extending the tile too far behind the fireplace surround). part of the tile is on the wall and the other part is overhaning into the insert. big difference in temps.

its such a small area the grout isnt going to move on you and the wall isnt going to get scorching hot. a fire place with a fan even less temp on the wall.

the thinset is also grabbing the backs of the mosiacs and the grout is helping keep everything is place. so the mesh is on the cement board not being exposed to the hot air.