I have a bathroom, already sheetrocked with the green moisture resistant sheetrock.

My tile guy told me I need to do hardiback for him to tile on, for the shower/bath's tiling on the wall.

Rather than ripping out the green sheetrock and redoing it in hardiback, my plan is to staple up a vapor barrier (just a 3-mil plastic dropcloth), and then screw 1/4" hardiback board over the top of the green sheetrock.

Can I reasonably do 1/4" hardiback over a vapor barrier over green sheetrock, for a tiled shower/bath?

  • You can do whatever you like. Your tile guy might not like your choice, though. 5 years down the line, you might not either. But if you are doing it to suit your tile guy, ask them. I know I'd kick anyone suggesting use of a 3 mil dropcloth as a vapor or moisture barrier offsite then and there. That's amateurish in the worst way.
    – Ecnerwal
    Aug 9, 2023 at 1:22
  • Green board can be tiled, but if you want it to last better use the fibre-cement. There no point half-arseing the fibre cement, you may as well stay with the green board, but it seems that to do that you will need a different tiler.
    – Jasen
    Aug 9, 2023 at 10:39
  • @ecnerwal I am an amateur. =P What should I do instead of plastic dropcloth, under the concrete board?
    – Jamin Grey
    Aug 9, 2023 at 17:34
  • @jasen My tiler will do whatever, hardieback was his strong suggestion. My question is, what should I do to make my bathroom last well long-term? Rip out the green sheetrock? Why should I not just do thin concrete board over the green? (the extra thickness will be easily hidden) And what would I put between the green and concrete-board? I want to do what's best here long-term, not what's easiest, short-term.
    – Jamin Grey
    Aug 9, 2023 at 17:37
  • @jasen Basically, I'm asking how to not half-arse it, because left on my own, that's what I'd accidentally do. =P
    – Jamin Grey
    Aug 9, 2023 at 18:05

1 Answer 1


Glue and screw the cement board to the green-board.

Use 1 1/2" screws to anchor the panels to the studs.

Forget about the plastic. Seal the walls and the floor with a waterproofing and uncoupling membrane such as AquaDefense or Red Guard

If your tile guy doesn't like that, you need a new tile guy.

  • Am I sealing under the hardiebacker, or am I sealing over the hardiebacker? The floor is concrete, do I still seal the floor?
    – Jamin Grey
    Aug 9, 2023 at 17:46
  • you apply the water sealer to the hardiebacker, then tile over that. Water sealer should be applied to the floor of the shower, if you do not have a PVC liner.
    – RMDman
    Aug 9, 2023 at 17:57
  • The shower is also a bathtub, so the "floor" of the shower is the bathtub (the floor of the entire bathroom is concrete, on the ground floor of the house, but raised above outdoor ground level) Do I still seal the concrete floor under the bathtub?
    – Jamin Grey
    Aug 9, 2023 at 18:04
  • 2
    No, it is not necessary to seal the floor under the tub. The order would be: hardi over green board, sealer over hardi, tile over the sealer.
    – RMDman
    Aug 9, 2023 at 18:13

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