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Thread: A "quick setting thinset mortar" ok for bedding acrylic tub?

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    DIY Junior Member recountryman's Avatar
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    Default A "quick setting thinset mortar" ok for bedding acrylic tub?

    I'm unable to get structolite locally...heck one place told me supplier is behind in will be 2 weeks before it arrives. Going to install tub Friday and wanting to use something that has a quicker drying time as I'm in a time crunch as this is our only bathroom.

    So can I use a quick setting thinset mortar for bedding the tub? If not is there a mortar that has a quicker drying time? thanks

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    Moderator & Master Plumber hj's Avatar
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    The processs of setting a tub MAY take longer than the "fast set" will give you. Even a slower setting material will "harden" enough to do your job by the time you have the tub ready to use it.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    Most 'thinset' mortars are not designed to be thick enough, are quite sticky, and not what you need. Another choice is a sand topping mix (really cheap) that is mostly sand with some portland cement in it. You can buy it premixed at about a 3:1 sand/cement mixture. When used to make a shower pan, you generally want more sand in it, but for bedding a tub, the off-the-shelf version at 3:1 is good...the higher cement ratio means it squishes easier. Lay some piles out, squish the tub down so it is plumb and level, then leave it for awhile. If you try to make a solid bed at the right height, you'll likely never get it done. Mix in enough water so that it is damp, holds together if you squeeze a clump, but doesn't drip water. Using too much water can make it shrink as it cures. It doesn't flow, or act like a cement mix you'd use to make a sidewalk, or foundation...it will look sandy - more like wet beach sand.
    Jim DeBruycker
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    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Junior Member recountryman's Avatar
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    Quote Originally Posted by hj View Post
    The processs of setting a tub MAY take longer than the "fast set" will give you. Even a slower setting material will "harden" enough to do your job by the time you have the tub ready to use it.
    I have read that mortar will take about 48 hours to dry before tub is ready to be used. Is that about right?

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    DIY Junior Member recountryman's Avatar
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    Quote Originally Posted by jadnashua View Post
    Most 'thinset' mortars are not designed to be thick enough, are quite sticky, and not what you need. Another choice is a sand topping mix (really cheap) that is mostly sand with some portland cement in it. You can buy it premixed at about a 3:1 sand/cement mixture. When used to make a shower pan, you generally want more sand in it, but for bedding a tub, the off-the-shelf version at 3:1 is good...the higher cement ratio means it squishes easier. Lay some piles out, squish the tub down so it is plumb and level, then leave it for awhile. If you try to make a solid bed at the right height, you'll likely never get it done. Mix in enough water so that it is damp, holds together if you squeeze a clump, but doesn't drip water. Using too much water can make it shrink as it cures. It doesn't flow, or act like a cement mix you'd use to make a sidewalk, or foundation...it will look sandy - more like wet beach sand.
    Thats what I thought but in my research have read comments of people suggesting thinset. The sand topping with portland cement does it have a quicker drying time than mortar?

    I'm guessing the Quikrete Sand Topping mix 1103 is like what your referring to?
    Last edited by recountryman; 05-25-2011 at 05:23 PM.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    Unless the bottom of the tub is perfectly flat and parallel to the parts that need to be level, thinset is not, nor has it ever been a good way to set a tub!

    Thinset installed thicker than spec (typically about 1/4"), especially if it is a modified thinset, could easily take a couple of days to set up. Keep in mind that ALL cement based products are spec'ed at full strength at 28-days. Yes, they obtain most of their strength in the first couple of days, but in reality, they continue to get stronger for years.

    A sand topping mix would be hard overnight, and start to get hard much sooner. The Quikcrete product has a fair amount of cement in it. For about $5/bag, you can get what is called drypack from a masonary supplier, which has more sand in it. But, that would work...it will look more like cement than deck mud (which is used to make a shower pan). Because of the extra cement and water, it may shrink a bit more than a drypack would.
    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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    DIY Junior Member recountryman's Avatar
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    Thanks for all the info. To keep things simple just got mortar mix and told wife may be without a bath for a couple of days...old tub will be in back yard with water hose if she gets desperate or she can just go to her dads house to take a bath.

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