1/4" or 1/2" wonderboard for bathtub walls??

1/2"

Chuck

Definitely 1/2 inch but I would use Durock instead of the wonder board. If moisture gets behind the tile the Durock will hold up better.

1/2; 1/4" needs something behind it - no economy here, use the 1/2"

In response to my Durock comment, I stand corrected. I always thought that wonderboard would absorb water like MDF. After reading JazMan's comment I did some more research and found that water doesn't harm it. Thanks for the correction Jazman.