My wife wants a new tile bathroom floor. My subfloor is 1x6's laid at a 45deg. angle across the floor joists with 4x8 sheets of particle board on top of that. I want to take up the particle board and put down plywood on top of the 1x6's, but I'm not sure what thickness I should use. I understand that tile needs a strong support subfloor and hardibacker under the tile. So, I would like to know the suggested thickness of the plywood and hardibacker that I should use.

subfloor