# bathtub support



## abc (Jan 17, 2008)

I've got a large american standard cast iron tub (actually a whirlpool tub) that is mounted into a wood frame. the tub is floating - supported sole by the wood frame with no contact bewtween the tub and the concrete floor (slab foundation) below except, of course, for the drain. The high side of the tub is about 8-10 inches above the floor, the low side is much closer (a portion of the foundation has been removed to connect the tub to the drain). Here's the question - the frame around the tub is covered with tile. given the weight of the filled tub, all of the grout lines have broken and the tiling is no longer level or uniform. The prior owner simply caulked everything - multiple times. The result is a mess, and not well sealed. What's the best way to properly support the tub without removing it and starting from scratch? should i try and support the tub from below with fat mud? expanding foam? wood? Bear in mind that the only access is at the ends, through small access panels. thanks in advance.


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## Tommy Plumb (Oct 7, 2006)

I take it by floating you mean drop in style tub? I've never installed a cast iron drop in tub but with plastic or steel ones before installing it you put a pile of cement on the floor. You don't fill the whole box, just use enough cement is used so that the tub is toutching. Then while it's still wet you put the tub down into the cement which spreads out under the tub making a nice bed for it to sit in. 
I wouldn't think this is necessary with cast iron, it's done with plastic tubs because plastic isn't rigid like cast iron is. It sounds like the box wasn't properly built. I doubt putting cement under there now would do anything.


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## abc (Jan 17, 2008)

i'm not sure whether it is a "drop-in" tub. The tub has no base that it fits into. the tub has a ledge around the upper part that rests on the tile covered frame. There is nothing under the tub. The tub is essentially cantalevered because the only support is the upper edge of the tub resting on the tile-covered wood frame. Obviously, the weight of the tub is too much for the frame.


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## majakdragon (Sep 16, 2006)

Most tubs are supported by a board on the wall side that is properly secured to the studs. Foam will not work since it will depress when weight is added and stay there. You may be able to use wooden boards under it with shims to help support it. The cast iron is not going to flex so this MAY help.


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## Tommy Plumb (Oct 7, 2006)

This is a drop in tub.


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## ranman469 (Dec 25, 2007)

a drop in tub and all tubs need to be supported from the bottom. in one way or another. weither you build it up with wood or concrete.
look up the tub install specs on line


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## abc (Jan 17, 2008)

*more on my tub*

My tub is much more massive that that shown in the photo. Its positioned about three inches from the wall (which also has tile on it), so it is probably not supported by the wall (i can;t imagine that the wall could not support the weight of this tub). I guess I will try to put wood underneath with shims to try and support some of the weight.The only alternatice is to put a pile of concrete under it somewhere close to the middle (i could build a form for this). Any problem if concrete is in contact with cast iron?


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## CathrynH (Jan 9, 2008)

Hello
I am not a plumber, but an avid, eveyr night bather. If someone you love is going to be using this bathtub, please do not use concrete under it. The wood sounds great. Bathtubs that are resting on cement give a terribly cold bath, and the water doesn't stay hot long, and even if the water is hot, your derriere is cold! This is especially noticible with non cast iron tubs, but I am sensitive and notice it on any tub.
So please have mercy on future bathers - this is a detail many builders overlook, or just don't care about, but there is 
a reason not to use concrete under a tub!!
Thank you.
Cathy H in California - Imagine if I had experienced
a concreted tub in Wisconisin!


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## majakdragon (Sep 16, 2006)

The normal material used under tubs is mortar. A five gallon bucket of premix is dumped on plastic sheeting and the tub is set onto it. This is where the term mortarbed comes from.


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