Wedi Board or Hardibacker for wet room?

[MedhaG]

Hi everyone - we're doing up our house and installing a wetroom, tiles are 8mm 60cm x 120cm porcelain tiles. The floor is timber and the walls are a mixture of timber and brickwork. Would appreciate your advice on what our tiler should be using for the floor and wall substrate - Hardibacker or Wedi Board or something else? Our tiler is nervous about the tiles cracking as they're larger than standard tiles, and there could be movement in the timber.