Plywood or sheathing on interior wall question - Bathroom remodel

[mike48130]

No reason for the Hardi board over plywood. Use Schuster membrane over 5/8 ply. Avoid wafer crap. Hardi doesn't add anything to the mix other tha. Thickness. On floor, you do need proper rigidity, single sheet of ply might not be enough...
Oh, definitely add wood studs and cross block for handles. And write down or take picts of where you put them......

If you are tiling you need a backer. The backer protects the tile from the expansion of the wood and the grout cracking. The membrane is for waterproofing. They have some membranes now that are thicker and have raised profile to them that are supposed to do both. Mainly seen them used in floors. Good bracing with some type of hardy backer and skip the plywood.