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Thread: Setting tub

  1. #1
    DIY Junior Member lw211's Avatar
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    Default Setting tub

    Replacing old cast bath tub with new tub the old cast didn't have a mortar bed. New tub will have apron. Sub floor is not perfectly level, it is 1x8 boards. Have some questions about a mortar bed for tub install.
    1 Just mortar mix?
    2 How wet or loose should mud be?
    3 Do i set the bottom of the apron in the bed also? (Do i spread the mortar the whole area of the tub)
    4 How thick?

    Thank you. Larry

  2. #2
    Plumber jimbo's Avatar
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    Default

    Lightweight concrete like Gypcrete is good, heavy but fluid consistency.

    BUT, first, determine if the tub you are using REQUIRES or PROHIBITS underlayment. Varies greatly by type of tub.....get the manufacturers installation instructions.

    Do not bed the apron. You need to have a more or less level floor. The apron supports the front, and a 2x4 ledger across the back supports that. After those items are in place, then the mortar bed issue is per instructions.

  3. #3
    Retired Defense Industry Engineer jadnashua's Avatar
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    A bed does two things...compensates for an uneven floor and supports tubs that aren't real sturdy from deflecting. A CI tub is strong enough to stand on its own and doesn't 'need' a mortar bed. The feet do need to be supported.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  4. #4
    Moderator & Master Plumber hj's Avatar
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    Default tub

    What kind of tub. I have never used a mortar bed under a cast iron tub, and seldom use one under other materials either.

  5. #5
    Forum Admin, Expert Plumber Terry's Avatar
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    I've never bedded a cast iron tub either.

    I put a 2x4 on the back wall using a level,
    And then if needed, shim the apron. The apron like hj mentions touches the floor.

    With some fiberglass tubs, I may use some mortar.
    I don't use a full spread, but piles which can spread out a bit when the tub is dropped.

  6. #6
    DIY Junior Member joel_IL's Avatar
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    What material do you use to properly shim a cast iron tub? I want to make sure that my shims do not compress over time due to the weight of the cast iron.

    Thanks!



    Quote Originally Posted by Terry View Post
    I've never bedded a cast iron tub either.

    I put a 2x4 on the back wall using a level,
    And then if needed, shim the apron. The apron like hj mentions touches the floor.

    With some fiberglass tubs, I may use some mortar.
    I don't use a full spread, but piles which can spread out a bit when the tub is dropped.

  7. #7
    Moderator & Master Plumber hj's Avatar
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    Default tub

    You do NOT shim it. The back edge rests on a ledger board and the front side rests on its apron. If there are legs they are a bonus, but do nothing to support the tub.

  8. #8
    DIY Junior Member rtyrd_GUY's Avatar
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    Am planning to install Sterling Vikrel Ensemble on ground floor slab. Haven't torn out the old 1 pc fiberglass so don't know how level the floor is yet. Have recommended spun bonded underlayment as recommended by Sterling and may use if slab is ideal for that material. The install instructions don't suggest how much or if you multifold the stuff. They do say place the felt pad if provided. Many pros suggest throw it away and mortar. I also have mortar on hand and plan to use it as an option as Sterling suggests. You posted using visqueen poly for a cover over the mortar in another place but not so here. I was wondering if it depends on other conditions, type of tub, etc., that dictates use or not. Not to get crazy but could you quantify how much you would use in creating those 'piles' which spread when tub is set in. Also how many mil thick would you go on the poly? Like some others who have commented the waffle like molded tub bottom can affect how the mortar spreads, I wonder if this influences the decision for using poly either under, over or both sides of the mortar base. For a lot of us DIY'ers this seems to be a never ending dilemma. Having search extensibly for a consensus, I get the impression the pros go with the mortar. Appreciate all the good scoop on this forum. I don't think I would have tackled this project if not for the freely shared expertise passed along here. Thanks.

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