Type S Mortar bed for tub

Discussion in 'Shower & Bathtub Forum & Blog' started by patrick1, Nov 22, 2011.

  1. patrick1

    patrick1 New Member

    Messages:
    20
    Location:
    Napa, CA
    hey guys,

    Last night I set my bathtub in a bed of mortar. It is perfectly level now but I am not sure how long the mortar needs to cure for before we can shower or take a bath. It is the Sakrete type s pre mix masonry mortar from Home Depot. I mixed it pretty thick it so I am assuming the cure time would be a little less than if I made it watery.
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,138
    Location:
    New England
    Well, that isn't what I'd use, but after a day, it should be cured enough. All cement products reach their stated strength in 28-days, but reach probably 70% in the first day or so. The load on it isn't very much per square in, so it should be fine. Adding more water than stated, doesn't change the cure rate, but does affect the strength. Not enough, and it can't create all the bonds it should.

    The mixture doesn't 'dry', it gets chemically combined with the cement. Excess messes up the matrix, too little, and you get incomplete bonds. It has enough affinity for moisture that it will pull it out of the air to complete the matrix, but that takes time and can subject it to damage in the interim. A better substance is a sand mix (deck mud) or structolite for this application. Not sure what the lime (which makes it type S) will do in the long term...maybe nothing.
  3. dlarrivee

    dlarrivee New Member

    Messages:
    1,172
    Location:
    Canada
    Did you put a sheet of poly over the mortar to keep it from contacting the tub itself?

    I assume it's a acrylic/fibreglass tub?
  4. cacher_chick

    cacher_chick Test, Don't Guess!

    Messages:
    3,249
    Location:
    Land of Cheese
    I'm not sure where these fellas are steering you...... I know for a fact that Kohler recommends installing their acrylic shower pans in a bed of masonry mortar with no plastic or anything else. I wouldn't let them worry you.
  5. dlarrivee

    dlarrivee New Member

    Messages:
    1,172
    Location:
    Canada
    I guarantee they don't recommend a mortar with hydrated lime in it.
  6. cacher_chick

    cacher_chick Test, Don't Guess!

    Messages:
    3,249
    Location:
    Land of Cheese
    What comes with your guarantee? :)

    The technical support folks at Kohler specify portland cement mortar, which to my knowledge always has lime in it, no matter if it it is S, M, N, etc.
  7. patrick1

    patrick1 New Member

    Messages:
    20
    Location:
    Napa, CA
    the tub has a hard foam bottom. Its some type of Polycomposite tub.
  8. dlarrivee

    dlarrivee New Member

    Messages:
    1,172
    Location:
    Canada
    Portland cement doesn't mean lime...

    Mortar can be sand and cement...

    Can you show us where every manufacturer follows Kohlers suggestion of "masonry" mortar, or even just Kohler's?
  9. patrick1

    patrick1 New Member

    Messages:
    20
    Location:
    Napa, CA
    I didn't mean to start an argument, but I guess that happens in all forums lol... I just hope my tub is okay.
  10. dlarrivee

    dlarrivee New Member

    Messages:
    1,172
    Location:
    Canada
    I think it will be fine, you did a better job than most would just by using mortar under it.
  11. patrick1

    patrick1 New Member

    Messages:
    20
    Location:
    Napa, CA
    This is semi off topic but why does the manufacture say not to use a ledger? I didnt use one since the manual said not to but I dont understand why that would harm anything.
  12. dlarrivee

    dlarrivee New Member

    Messages:
    1,172
    Location:
    Canada
    Most of the newer tubs have supports built into them, they would rather you put your weight onto those supports.
  13. patrick1

    patrick1 New Member

    Messages:
    20
    Location:
    Napa, CA
    Oh I see, thanks for the info! There is about a 6 by 6 inch area under the the where I didn't put mortar since it was so close to the drain but looking at it from under the house it wont affect the drain at all should I mix a little bit of mortar and shove it into that void?
  14. dlarrivee

    dlarrivee New Member

    Messages:
    1,172
    Location:
    Canada
    Whatever gives you peace of mind.
  15. cacher_chick

    cacher_chick Test, Don't Guess!

    Messages:
    3,249
    Location:
    Land of Cheese
    I don't claim to know it all, but common Portland cement mortar used for masonry has hydrated lime in it. If you are thinking of some other product, so be it.


    I don't care to spend the time trying, even if I could.

    I was making a general statement to say that there should not be any problem with using the product that the OP used. I have some experience in building with fiberglass laminates, and I believe that what works as a bedding material for a plastic composite shower or tub should work fine for a fiberglass one also.

    I am aware of likely problems is one uses plaster or other gypsum-based mortars, but that would be another topic.

    No worries- I'm here to learn.

    I guess I could have just asked, but I was trying to lead you to explain why you might believe that the product that the OP used is a problem. If you can teach me something that I can research and find to be fact, then I will be all the better for it. :eek:)
  16. patrick1

    patrick1 New Member

    Messages:
    20
    Location:
    Napa, CA
    Well all of my creaks are gone and the tub feels very sturdy now.I guess the mortar did its job lol.
Similar Threads: Type Mortar
Forum Title Date
Shower & Bathtub Forum & Blog What type of mortar for Acrylic tub mortar bed Jan 14, 2014
Shower & Bathtub Forum & Blog Mortar type? Feb 10, 2008
Shower & Bathtub Forum & Blog What type of repair options available for tub coat peeling? May 22, 2014
Shower & Bathtub Forum & Blog Can this type diverter valve leak behind the wall? Oct 18, 2013
Shower & Bathtub Forum & Blog type of p-trap for tub drain Jul 8, 2013

Share This Page