Walls and Ceilings - tile on drywall for fireplace surround

First, let me describe what I'm dealing with, then my problem. I hung drywall over my cinderblock fireplace recently. There is a slight space between the drywall and cinderblock where ribs help keep the drywall level. Since I want to use the fireplace, I planned to tile the surround. My concern is that since the drywall isn't directly touching the original fireplace, it won't be able to support the weight of both concrete backerboard and tile. I thought about using concrete screws to fasten the backerboard through the drywall and into the cinderblock, but now I wonder if that would be strong enough to keep the tile from cracking down the road. Is this a legitimate concern, and if so, can anyone help suggest a way to accomplish this task? Thanks!

Welcome to the forum

If I understand correctly, you need to cut out the drywall where the tile will be and install wonderboard [cement board] You would install it by both using thinset [to glue it to the block] and concrete screws. Hopefully this will bring it out flush with your drywall. If not, use of trim [wood or tile] can help make the transition.

Thanks! Is that necessary only if I want the tile to be flush with the drywall? Or would you recommend that I cut the drywall anyway since it wouldn't be strong enough to support the tile on top of it? I probably wouldn't mind if the tile wasn't flush with the drywall (it certainly would be easier than cutting the drywall) - I'd add a border around the tile to make for a nice transition. But the big question is whether the drywall would even be strong enough to support concrete backerboard and tile if the drywall is spaced from the cinderblock fireplace.

I wouldn't put tile on drywall that isn't properly supported. That is why I suggested removing the drywall and using wonderboard direct to the block. The wonderboard can be secured to the block giving a solid surface to tile.

Thanks Mark!