How thick should my backerboard be for a bathroom floor?

Dear Sir,

What you haven't told us is the thickness of your plywood, joist spans, etc to ensure that even 1/2" would be sufficient. That said, there is nothing wrong with using 1/4" on floors. You also have very small tiles which will help prevent tile cracking.

Hope this helps, William

Well, the plywood appears to be 1/2". I haven't pulled up the linoleum yet, so I can't see the joist spans. Can you tell me what considerations would force me to choose 1/2" backerboard? Thanks!

Greetings,

" a.. Use minimum 5/8" exterior grade plywood or 23/32" exterior grade OSB, complying with Local Building Codes and ANSI A108.11, over joists. Joists' spacing not to exceed a maximum of 16" on center.

a.. Deflection must not exceed L/360 of the span, including live and dead design loads.*

a.. Do not use glue between grooves of tongue-and-groove subfloor to allow for expansion and contraction of subfloor. "

Please read the following

I had just eyeballed the plywood, and now I have measured it to 5/8". There is also a tongue-in-groove under the plywood, I believe. So it sounds like 1/4" HardiBacker will be OK, rather than my 1/2" Wonderboard, assuming all the other specs meet standards once I pull up the linoleum.