I see cement board is reccomended for shower areas and not purple drywall, pretty much everywhere.

However, in pretty much all those cases they are talking about where the shower area will be tiled. Is it okay to use purple drywall if you'll be using a shower surround and not tile?

  • Whichever you decide to use it would be a good idea to put horizontal blocking between the studs at the appropriate height for horizontal grab bars on all three tiled walls of the shower enclosure. The minimum width would be 2x6" and most installations go larger than that, 2x8" or 2x10". That allows flexibility in chosing the height of bars. Commented Mar 19, 2023 at 21:37
  • Why any type of drywall at all? Better shower surrounds can be attached directly to framing, needs no underlayment. Any type of drywall will deteriorate badly if not kept dry. Plywood is superior in all respects. Always allow for thermal expansion of surround panels, do not allow to sit on tub, etc., caulk joints will fail otherwise.
    – kreemoweet
    Commented Mar 6 at 1:33

3 Answers 3


I tend to view this choice in terms of the overall project cost.

There's a difference in price of materials, but on the complete project scale, the cost difference is minor. With tile, it's a trivial choice, since the cost of tile (materials and labor) is far above the cost of the backer, and providing tile with inferior support is potentially a very costly decision in the long run.

With a surround, you still have some potential for water ingress, particularly if it's multi-part and depends on caulking to seal the seams; and backerboard is still far better at handling water exposure than "moisture-resistant" drywall, but there's very little labor cost in the surround, and it "should" be waterproof.

The small incremental cost on the whole project scale still favors using the better product by my math. Your math may be different.


In a perfect world, using the purple drywall should be fine for a surround. The problem is you still have to cut the surround for your valves and shower head. You might want to install a grab bar at some point. These areas now have to be caulked and we all know that caulk fails over time. Even the seams of the surround have to be caulked. The cost differential is minor compared to a redo.


Cement board has far better resistance to moisture, However purple drywall is fine when using a surround.

  • By a surround do you mean plastic or fiberglass? I personally like the idea of using this rather than ceramic tile with all th e problems with mold on the grout. But if the surround doesn't have built in grab bars it would seem advisable to put in horizontal blocking (in the correct plane) for later fxing of grab bars. Commented Mar 19, 2023 at 21:49
  • @JimStewart, when I said "surround" I was referring to any type of enclosure that was not tile. The question had no reference to grab bars and any needed blocking, so that was not a factor in my answer.
    – RMDman
    Commented Mar 20, 2023 at 0:29

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