how to tile a fireplace to the ceiling (floor, paint, slate)

[michaelj314]

I am wanting to tile a fireplace from the floor to the ceiling. The fireplace wall is 7 feet wide and 10 feet tall. The tile is a porcelain 12 in by 24 in. The fireplace is non venting without a stack and has no brick, only drywall above and beside the opening for the firebox. There is 1 row of slate tile surrounding the firebox that will be removed. We are replacing a non venting gas system with a electric system. My question is: can I tile over the drywall with just mastic or should I put any hardibacker type product over the drywall? Will the drywall hold the weight of the tile? Currently, there is a coat of waterbased paint on the drywall. I just want to be sure that the drywall will hold the tiles. any thoughts?

[K'ledgeBldr]

Durarock over the drywall, thinset mortar.

Drywall alone (especially painted) is not a good substrate for tile (especially tile that size). Mastic is not recommended for tile that size.

I don't like Hardi-backer; it's too flexible.

As long as the screws you use to attach the Durarock go into studs, they should penetrate the stud at least and inch.