Is 15/32" plywood thick enough to be used as a subfloor under tile combined with a 1/4" hardiebacker board?
The joists underneath are 2x8s that are 16" apart on center and only 4' long.
Wood – Is 15/32″ Plywood okay for Subfloor under tile
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Best Answer
Most tile and mortar manufacturers want 1-1/4" (nominal) even with polymer-modified mortar. While your joists are unlikely to flex, the subfloor might. I'd use 1/2" cement board if height isn't a critical concern.
Alternatively, block between your joists on 16" or 19.2" centers. Even vertically-oriented 2x4s would do if fastened well.