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Thread: Cement under whirlpool tub

  1. #1

    Default Cement under whirlpool tub

    Which type of cement mix is best to use under a whirlpool tub for the bedding?

    I think I heard that a mortar mix is best, but I would like to find out before I buy the wrong stuff.

    Also, how much should I buy? 2 or 3 bags at Lowes?

    I'm installing a whirlpool tub in our bathroom and in case it needs to be removed in the future, I'm planning to put a very thin plastic film (cheap painter's "drop cloth" plastic) on top of the cement so that it doesn't adhere to the tub. Any problem with that?


    Thanks
    Steve

  2. #2
    Plumbing Designer FloridaOrange's Avatar
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    Not a complete answer to your question, just something to think about.
    If your whirlpool tub is anything like my brother's, it is made of fiberglass.
    The mortar bed is to keep it from moving as well as giving support. Your idea of plastic film will defeat the purpose of keeping it from moving. Fiberglass and movement results in the fiberglass wearing at the contact point. Your idea may void any warranty with the tub as well as cause you problems. If it isn't installed for a long time you may not damage anything.....but maybe you will. Feel like rolling the dice?
    Matt
    Semi-professional plumbing designer
    Enjoying life in SW Florida

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    Moderator & Master Plumber hj's Avatar
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    Default tub.

    YOu want a material that can spread easily as the tub presses down onto it, so you do NOT want any cement with stones in it, such as premix concrete. MOST plumbers put the plastic, or something, between the tub and the mortar. Sometimes we use a bag of premixed perfatape cement with cuts in the plastic bag to let it expand. How much you need depends on how much space there is between the bottom of the tub and the floor.

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    Sound and Light Suppervisor for a School District tjbaudio's Avatar
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    Quote Originally Posted by FloridaOrange View Post
    Not a complete answer to your question, just something to think about.
    If your whirlpool tub is anything like my brother's, it is made of fiberglass.
    The mortar bed is to keep it from moving as well as giving support. Your idea of plastic film will defeat the purpose of keeping it from moving. Fiberglass and movement results in the fiberglass wearing at the contact point. Your idea may void any warranty with the tub as well as cause you problems. If it isn't installed for a long time you may not damage anything.....but maybe you will. Feel like rolling the dice?
    The instructions with my fibreglass shower unit required a plastic layer between the base and mortar. It also required some wood blocking at specific points on the wall and floor. Check your installation manual BEFORE you mix up the bag.
    tjbaudio
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    Plumbing Designer FloridaOrange's Avatar
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    Quote Originally Posted by tjbaudio View Post
    BEFORE you mix up the bag.
    Good point. My experience was only with my brother's tub.
    Matt
    Semi-professional plumbing designer
    Enjoying life in SW Florida

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