Bathtub Mortar Bedding

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mattyoungus

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Hi,

I have a couple of questions about mortar bedding for a bathtub install:

  1. What type of mortar should be used?
  2. Why would you fill the tub up, and let it sit for 72 hours?
Regarding the second question, it seems ccounterintuitive and I've read on several posts that this is the way to do it. If the whole point of the mortar bed is to stop the tub from flexing with weight, why would you want to add weight while the mortar is setting. Then, you drain the tub and it wants to pop up from the bed. Seems to defeat the purpose of the mortar bed in the first place.

Any thoughts...
 

Jadnashua

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Mortar does two things: it helps support the tub to make it feel much more robust and it affords you an opportunity to ensure that it is properly leveled. You need a mortar that won't 'slump'. Something like deck mud is more like wet beach sand will work. Make piles of it, and it's almost impossible to provide all of those functions by leveling the mortar bed first. When you set the tub down, you will be compressing the mortar, it will spread out (but not perfectly). You'd typically have installed some ledger board(s) and if you do that correctly, you can push the tub down until it contacts the ledgers, and it will be level. Water in the tub helps to apply even pressure all over. It doesn't need 72-hours to set, though! Overnight should be more than enough. You'd often want to put something like plastic or tar paper on the floor to help prevent it from sucking moisture out of the mortar, which will weaken it. You can put a layer over the top between it and the tub if you want. Depending on the type of mortar you use, some of them will bond to the tub, and it makes removal down the road easier. Some people use a light mix like structolite.
 

ShowerDude

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quickrete 5000 works great for tubs as do many other..

I do fill the tub while it sets up even with a mudbed, stay away from the foam approach.
 
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