Waterproofing Under Acrylic Shower Pan

Discussion in 'Shower & Bathtub Forum & Blog' started by Outdoorbum, Jun 15, 2021.

  1. Outdoorbum

    Outdoorbum New Member

    Joined:
    Feb 24, 2021
    Location:
    Oregon
    Does anyone have a suggestion or advice for waterproofing under an Aquatic brand shower pan? I've read posts that say its not necessary, but after replacing rotted subfloor from an old tub, I have no problem with overkill if it prevents water damage. I thought about Redguard over the plywood subfloor, but also considered maybe an Oatey liner?? My fear is a hairline crack or drain leak will go unnoticed for a while, and then I'm back to square one in a few years.

    Intuitively, just setting an acrylic shower pan on subfloor seems risky with no backup plan.
     
  2. Terry

    Terry Administrator Staff Member

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    Aug 17, 2004
    Occupation:
    Plumber
    Location:
    Bothell, Washington
    The pan has a drain that fits into a hole in the plywood. I've never seen a problem under an acrylic or fiberglass pan, but if there was one, the walls were also bad. It seems if the walls are in good shape, the water winds up in the pan.
     
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  4. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    Retired Systems engineer for defense industry.
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    New England
    THe biggest failure point on a receptor (manufactured) pan is from a failure in the pan from lack of proper support. The material tends to be flexible. Just like it takes time to break a wire coat hanger by bending it back and forth, eventually, it breaks.

    Some pans say support underneath is optional...IMHO, it's mandatory if you want it to last.

    The other thing that can cause problems is when the pan is not level, as most floors aren't perfect. Nor are the walls. Depending on what you're using for walls, making sure what's underneath is flat and plumb is worth the effort, then the walls and pan will fit properly. By using the support material under the pan, you can also level it.
     
  5. Tuttles Revenge

    Tuttles Revenge In the Trades

    Joined:
    Oct 15, 2014
    I think it would be extremely difficult to actually water proof under a shower pan. You might lay a sheet of plastic down that goes up the walls to divert water towards the drain hole in the sub floor.. but as stated above, if its installed correctly with proper support and quality products on the drain and those installed correctly it should last a Long time.. But in the end.. everything will fail eventually.
     
  6. Outdoorbum

    Outdoorbum New Member

    Joined:
    Feb 24, 2021
    Location:
    Oregon

    What support material would you suggest under the pan?
     
  7. Outdoorbum

    Outdoorbum New Member

    Joined:
    Feb 24, 2021
    Location:
    Oregon
    Also, if the surround walls are also acrylic (part of a kit) would you put a vapor barrier behind them on the studs? I plan on having unfaced insulation in the walls, and 2 of the walls are exterior walls. I understand that its possible to get condensation on a barrier if its hot outside and cooler in the house, and I've read pros and cons to having a vapor barrier.
     
  8. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Joined:
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    Occupation:
    Retired Systems engineer for defense industry.
    Location:
    New England
    Often, people will staple some roofing felt or plastic to the floor, then put piles of (brick) mortar on it, then smush the pan in place, ensuring that the relevant edges are perfectly level so the doors and walls have a better chance of lining up. You do not want to try to make a full coverage, as you won't be able to level things since the bottom of the pan is often not flat by itself. Some will use a product like Structo-lite which is a plaster product rather than a cement based product. The layer on the floor is to help prevent the stuff from getting the moisture sucked out of it while it sets up, and it can help during remodeling by making it easier to remove that layer.
     
  9. Outdoorbum

    Outdoorbum New Member

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    Feb 24, 2021
    Location:
    Oregon
    I got an Oatey liner that will fit perfect in the alcove and I like your suggestion as opposed to just putting the mortar straight on the subfloor.
     
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