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Thread: Installing plastic tub - mortar bed?

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    Engineering Technician The old college try's Avatar
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    Default Installing plastic tub - mortar bed?

    I'm getting ready to install my tub (hopefully tomorrow) and I'm not really excited about the way it feels during a dry fit. When I step in the tub is feels like it sinks slightly before resting on the bottom supports. The instructions say that it should be placed either directly on plywood or if another substrate is used, housewrap material or spunbound landscape fabric should be laid under to prevent squeaking. I'm wondering if I should place it in a bed of mortar with tyvek between the mortar and tub so that it's supported and won't move up and down once installed. This is my first tub installation, so any advice is greatly appreciated.

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    DIY Senior Member TedL's Avatar
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    Use the mortar. Search for a post by Terry describing using "piles" of mortar.

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    DIY scratch-pad engineer leejosepho's Avatar
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    The way the tub has been built can make some differences here -- some tubs already have a fairly solid bottom-support system built into them, and others do not. With tubs that already have solid and flat bottom supports made of heavy plywood or some other material, I remove the stubby legs and build a simple framework of treated lumber as a foundation for the entire bottom.

    If you are going to use mortar and your tub does not already have a solid bottom, pillars of mortor would not be a good idea. With pillars (rather than an overall pile), you could end up with voids where the tub bottom can still flex, and that is what needs to be eliminated altogether.

    It sounds to me like your problem is simply a matter of those little legs being a bit short (or the skirt a bit long), and you should definitely resolve that matter before actually installing the tub and supporting its bottom in whatever way.

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    Engineering Technician The old college try's Avatar
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    Thanks for the advice. I read through a bunch of the mortar bed posts last night. In fact, one of the posts includes pictures of the exact same tub installed over a bed of piles, and it installer said that it turned out real well. I guess my major concern is wondering if the mortar will negatively react with the materials the tub is made of, and secondly I'm having a difficult time narrowing which type of mortar to use. I've seen different types mentioned, but I want to make sure I get the right stuff. The guys at the big box stores are bigger toolbags than me, so I'd rather take the advice from pro's like you guys rather than from someone who pretends they know it all.
    Last edited by The old college try; 03-04-2007 at 06:09 AM.

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    DIY scratch-pad engineer leejosepho's Avatar
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    Quote Originally Posted by The old college try
    I guess my major concern is wondering if the mortar will negatively react with the materials the tub is made of, and secondly I'm having a difficult time narrowing which type of mortar to use.
    I am not aware of any incompatability issues, and my personal experience with thinset is that is not suitable for a thick pour as it shrinks quite a bit during curing ... and the avoidance of that shrinkage (as well as the weight of around 3-or-so cubic feet of concrete) is why I still prefer to place a well-built and right-fitting wooden framework underneath.

  6. #6
    Retired Defense Industry Engineer jadnashua's Avatar
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    Some people use strucolite (sp?). Deck mud (a mix of sand and portland cement 4-5:1 sand to cement also works well. Mortar probably would work, but costs more.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    Homeowner geniescience's Avatar
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    Default the more sand the better

    sand does the job required here.

    Four or five parts sand, one part cement. A sand mix in a bag is that already.

    David

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    DIY Member JohnD's Avatar
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    The guys at the big box stores are bigger toolbags than me, so I'd rather take the advice from pro's like you guys rather than from someone who pretends they know it all

    I've been doing this for 8 years and working @ a big box the last year mostly for health insurance. I would imagine that you are one of the jack legs that come in and don't know the difference between a compression and a flare fitting. If you really want a plumbers expertise I suggest you hire one.

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    DIY Senior Member TedL's Avatar
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    Quote Originally Posted by JohnD
    The guys at the big box stores are bigger toolbags than me, so I'd rather take the advice from pro's like you guys rather than from someone who pretends they know it all

    I've been doing this for 8 years and working @ a big box the last year mostly for health insurance. I would imagine that you are one of the jack legs that come in and don't know the difference between a compression and a flare fitting. If you really want a plumbers expertise I suggest you hire one.
    How many of your co-workers share your level of expertise?
    How do I tell you part from the others? (I do occasionally try to find some expertise at the big boxes, looking for guys over 50 who look like they're moving a little less quickly because of years of beating on their body. There's one at one nearby HD, but unfortunately he has a crappy hearing aide that makes conversation difficult.)

    I don't blame the kids who are sent to work in plumbing, I blame the stores.

    But I've also gotten blank stares from 30 somethings at plumbing supply houses when I've asked if they have ABS fittings.

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    DIY scratch-pad engineer leejosepho's Avatar
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    Quote Originally Posted by TedL
    ... looking for guys over 50 who look like they're moving a little less quickly because of years of beating on their body ...
    Yes, several such fellows come to mind, and I often wonder who will ever replace them. Some of those guys may have already forgotten more than most people will ever know.

  11. #11
    Engineering Technician The old college try's Avatar
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    Quote Originally Posted by JohnD
    [I]
    I would imagine that you are one of the jack legs that come in and don't know the difference between a compression and a flare fitting. If you really want a plumbers expertise I suggest you hire one.
    Flare? Isn't that one of those things that truckers put on the on the road when they get a flat?
    The tub install went great. Used ready mix quickreat mortar and the tub feels solid.

    Thanks all!,

    The Jackleg.

  12. #12
    Master Plumber Dunbar Plumbing's Avatar
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    Quote Originally Posted by The old college try
    Flare? Isn't that one of those things that truckers put on the on the road when they get a flat?
    The tub install went great. Used ready mix quickreat mortar and the tub feels solid.

    Thanks all!,

    The Jackleg.

    No, I think he means Rick Flair, that wrestler in the WWF that would beat everyone up with a folding chair.

    Tuff I say, tuff!
    Read what the end of this sentence means.

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