I had a plumber install a shower pan yesterday and he seemed annoyed I asked him to install it in a mortar bed even though that's what the instructions said. I already have an issue with the fact that he used concrete with lots of big rocks instead of thin set but my biggest question is whether there is supposed to be the big gap between the floor and the bottom of the pan? From what I read the pan should be touching the floor but as you can see in the photos it is elevated 1/2" - 3/4" off the ground. It seems like he did not push it down far enough into the mortar. I can also stick my fingers in the gap about 2" before I actually feel any of the concrete mix. Is this acceptable? What are my options at this point? Do I have him redo it? Will that ruin the entire pan trying to take it out? Do I just try to add plywood underneath to fill in the gap? gap

shower pan


1 Answer 1


Did you Read The Functional Manual?

Concrete or plaster is not recommended.

It will be necessary to push the shower base until ... the front edge is contacting the rough floor along the entire length of the shower base.

The fact that large aggregate is present is the problem. This was objectively done incorrectly and in violation of the instructions provided by the manufacturer.

I would withhold payment and find a plumber who cares about their work.

If you would rather deal with it yourself, you'll need to remove the pan and scrape away the concrete. Don't try to retroactively support the front flange. The faulty concrete could result in pressure points that damage the pan floor, and there's a good chance that it's out of level.

  • The plumber told me I worry too much when I asked a different question. I also tried to show him the directions and he just acted like he knows what he's doing. I'm unsure how to confront him about it as I know he'll think he did it right. He has already done some other plumbing work that I owe him for so I'm not sure how much to withhold. My dad claims it should be fine if we just add plywood + thinset underneath the front flange but I worry about damaging the pan or it cracking. It really is hard to find someone who does quality work May 11, 2023 at 15:02
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    Withholding is (1) the time he wasted and (2) the time it’ll take you or someone to remove the concrete and possibly (3) replace the pan if it was damaged in removal. This resets the clock and now you can pay someone else to do it right. Document every conversation; keep photos. Make sure he knows you’re documenting. Be firm: he didn’t follow manufacturer’s instructions and it needs to be made right. May 11, 2023 at 19:36
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    I wonder if any legal eagles can tell us whether a contractor is implicitly required to follow manufacturer instructions for something like this, from a contractual standpoint.
    – isherwood
    May 11, 2023 at 19:37
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    @isherwood sounds like a good question to ask on the law stack
    – mmathis
    May 12, 2023 at 0:12
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    @isherwood - not a lawyer, but I'd guess it's a "no one ever got fired for buying IBM" situation - following the manufacturers instructions show you are following best practices. If you're sued, you can point to the instructions, say you followed them, and then the person suing you would have to go after the manufacturer. If, however, you do your own thing, you'd have to demonstrate in court that your installation process was sound, which is considerably more difficult. You'd also have cut off the person suing you from suing the manufacturer, as they'd simply claim improper installation.
    – lupe
    May 12, 2023 at 8:59

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