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I'd like to replace my aging PVC tub surround with an inexpensive acrylic 3-panel one. Assuming I am down to bare studs after removing the existing surround (perhaps the backing wall will be damaged), what must I install on top of studs before I can glue the acrylic panels?

If it's a cement board, like Durock, Hardibacker, or Wonderboard, do I need to apply a waterproofing membrane (like RedGard) as well?

Nikita
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2 Answers2

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I use green board for this with redgard over in some cases (cheaper systems that don't overlap well). My take on it is if there is a water issue. I would rather the water be trapped in drywall and mold vs. drip down into stud bay and rot the wall or what is underneath it.

Taking out plastic sheets to repair a wall and adding more drywall is easy. The alternative isn't. Also my biggest concern with backer is the hollow sound it often projects when PVC surrounds are glued to it. Sometimes it sounds/feels like you are in a tin can.

This is all opinion though and you can go with backer or greenboard and regard or not. Local inspectors that I have dealt with don't care at all about whats behind tub kits. They are fine with putting it directly on studs. Really if installed right and caulked properly you shouldn't ever have a water issue. That is why I choose to go with what gives the best experience.

DMoore
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  • sorry, are you suggesting plain green board - with no water-proofing membrane over it. So glue tub surround wall panels directly on it? Is that sufficient? My understanding is that green board is NOT water proof (just resistant) and that no matter now good the caulking of the surround panels, one has to expect that some moisture will get through to green board. – Nikita Dec 17 '14 at 22:52
  • That would be my suggestion - redgard the greenboard if you are truly paranoid. If you do that though try to make sure the redgard wicks over the tub lip which may be impossible with some kits but possible with others. Where do you think the water will go if you install something that is "waterproof"? – DMoore Dec 17 '14 at 22:59
  • roger. to answer your q - not sure. Your initial answer made logical sense to me, must have read too many 'everything will leak' posts. Ironically, RedGard mfr says that RedGard makes for a poor adhesive base so smearing it may create a new issue ;- – Nikita Dec 18 '14 at 00:42
  • @nikita - regarding redgard... exactly. – DMoore Dec 18 '14 at 03:27
  • Greenboard is typically not an acceptable shower back. I don't know if it's allowed when adhering a PVC surround. – Matthew Dec 18 '14 at 18:40
  • @Matthew - You are correct. Except the PVC surrounds are the only exception (some counties let you do greenboard for granite/marble slabbing too). I have yet to go through an install and have an inspector say anything. Obviously the greenboard is mentioned in my permit plans so they would usually bring it up then. – DMoore Dec 18 '14 at 19:06
  • Green board can also be used behind tile membranes such as Schluter Kirdi. – Chileab Construction Dec 19 '14 at 09:45
  • @ChileabConstruction - Correct. But you aren't installing on greenboard, it is on the kerdi membrane. In my area the redgard debate is beginning because people want to tile tubs with greenboard plus redgard. Some inspectors OK it some don't. I personally think it is fine but haven't done it. – DMoore Dec 19 '14 at 19:17
  • DMoore - oh my. I can't imagine tiling on redguard over green board, Denshield ok but greenboard? It is just too easy to leave small pin hole gaps in rolling or brushing it. Hope the the homeowners get a good 12 year warranty. – Chileab Construction Dec 21 '14 at 00:31
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One disadvantage of direct to stud stalls is the lip at the outer edge over which the drywall will be applied - this causes a hump in the drywall surface. I usually fir out the studs with drywall shims so that the drywall lays flat onto the fiberglass or acrylic lip.
I would recommend using water resistant drywall for all the areas around the shower.

Chileab Construction
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