Plywood or Chipboard under Backerboard?

[hammerandnails]

Hi all,

Quick question, when installing 6mm backer board onto a floor prior to tiling, would you prefer plywood or chipboard underneath?

Also, do you use adhesive and screws to fix the backer board down, or just screws?

For reference, it would be 22mm thick either way, and if chipboard it would be the P5 moisture resistant stuff. If plywood, it would be sealed properly with SBR before installing backer board. Suspended timber floor underneath.

Thanks

 

[hammerandnails]

Any thoughts from anyone?