Bricks, Masonry, Asphalt and Concrete - tile behind woodstove

I'm planning on using wonderboard mounted on ceramic risers behind a woodstove. My problem is this. I'm using half inch board attached to wall studs every sixteen inches or so. Even with this many the board still has movement when pushed. It bows under pressure. I plan on putting ceramic tiles over the wonderboard but am concerned that the flex in the board will screw things up.

I'm pretty sure that this is fairly standard stuff for behind a stove but I can't figure out how the smart guys install it to make it rigid.

Thanks

Derek Roberts

If you use thinset mortar to bond the tile, thats where you pick up your strength....or if you still cant sleep, go ahead and put a sheet of 3/8" ply first, then the wonderboard (1/4"ply will do). Screw the wonderboard with Drywall screws, nails can losen. Ok to nail the ply , use 8 penny sinkers(2-3/8"). But really the mortar and the grout
right over Mr Wonderboard,..should be fine.......
good luck
ryk

Forget the ply,..that could be a fire issue, depending on the stove clearance,...Use 5/8" Drywall,..that has a 1 hour fire rating as well,..built in...and it will provide that
easy sleeping,secure tile backing that we all search for !!
Good Luck
ryk

Thanks for the suggestion. I like the idea of drywall to add rigidity. In fact, there's a fire rated drywall that is often code for walls between garages and living spaces. I might use that stuff as backerboard for the wonderboard (backerboard!). A bit of thinset and grout and it should hold really well. I'd rather over-build here anyhow than have cracking grout and falling tile later.

Thanks again,

Derek