Granite tile over steel surface, Tile Gurus please help.

I'm planing on applying 12" X 12" granite tiles to the front surfaces of a steel fireplace insert. It has bee suggested I use mesh attached to the sheet metal with screws and use mastic. The person who suggested this said the trick wasn't getting them to stick, the trick was getting them to stick for 20 years, and I agree. I'd prefer not to have to deal with the added thickness of the mesh. I had a thought; perf the sheet metal with a drill to give the the mastic something to grip. Any thoughts on this
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Eric in North TX writes:

What kind of metal?
Scrub on a layer of epoxy for a bond coat.
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Hi Eric, I am not sure of the type insert you have but I think I have an idea of how it is inserted into your wall. With that in mind, you should have your wooden mantel on each side & top.
Have you considered attaching a solid surface over the face of the unit & wall such as durrock then glue your tiles to this. That way you could attach the durrock onto the wall around the insert allowing it to cover the metal of the insert & butting it to the wood mantel on each side.
I do not think I would drill holes in the insert or add screws. It could lead to leakage of heat and/or smoke, not to mention the warranty on the insert if that applies.
Hope that helps. Abart
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it won't stick well, or at all. if it does, then the flexing of the steel (either pushing against it) or from heat expansion, the tiles will pop off or the grout will crack anyway.
attach cement board in front of it, then thinset the tiles to that.
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That's the reasoning and experience, I'm asking for. Again, I'm doing this for the long run. I don't intend to use it for burning wood, my wife is allergic, likely a gas or electric log set (if I can find one that looks even remotely like a fire). Still, even a gas log set would make enough heat to make steel walk a bit, I hadn't considered that.
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