Tub Install ?
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Tub Install ? (by Frank [NJ]) Jul 7, 2019 7:25 PM
       Tub Install ? (by #22 [MO]) Jul 7, 2019 7:37 PM
       Tub Install ? (by RR78 [VA]) Jul 7, 2019 8:05 PM
       Tub Install ? (by Frank [NJ]) Jul 7, 2019 8:35 PM
       Tub Install ? (by Steve [MA]) Jul 7, 2019 8:50 PM
       Tub Install ? (by RR78 [VA]) Jul 8, 2019 12:52 PM
       Tub Install ? (by MikeA [TX]) Jul 8, 2019 7:48 PM
       Tub Install ? (by MikeA [TX]) Jul 8, 2019 7:50 PM
       Tub Install ? (by Vee [OH]) Jul 8, 2019 8:22 PM

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Tub Install ? (by Frank [NJ]) Posted on: Jul 7, 2019 7:25 PM

Hi All:

We ae reno'ing our main bath and have a problem someone here may have had before.

The tub plumbing is roughed in and the tub secure against the left corner & pipe area and the rear wall. I have a pro doing the plumbing and today he tells me that the 3/4" fir plywood floor has a belly in it.

It starts about 6" from each edge corner and runs the remaining length of the tub. The first fix he has floated was to be putting wire mesh & mud underneath it.

I am not averse to that but thought it sounded kinda weird to me. He has no intention of removing the tub & reinstalling.

I took a yardstick and ran it from front to back and the "belly" seems to be pretty evenly spaced and the stick moves freely.

The belly does not seem to be much deeper than the thickness of a yardstick.

I guess that if the tub is not completely in contact with the floor that it could crack with weight of water & occupant.

He talked about putting wire & mud underneath or somehow shimming it. A friend carpenter I know said there is is "lath" that comes in 2'x4' or maybe 8 ft. sizes for such a situation. Is that so.....as he did not know where to get it.

Does anyone have any suggestions?

It an Americast tub by American Standard.

As always I am thankful for the help available here. --74.105.xxx.xxx

Tub Install ? (by #22 [MO]) Posted on: Jul 7, 2019 7:37 PM

If this is an older tub, I'm guessing it's stood the test of time. I try and get the plumbers to set tubs in concrete, but it doesn't always happen. If the tub isn't in great shape, I'd put a new one in... you'll never get a finish better than the factory's. If you're intent on leaving the tub as it sets, trying to get some concrete or floor patch under it sounds fine. It sounds like a steel or cast iron tub... it likely won't need the support I'd guess. --173.25.xxx.xxx

Tub Install ? (by RR78 [VA]) Posted on: Jul 7, 2019 8:05 PM

I would have him reinstall the tub. After floor leveling.

Checking the floor should have been step one.

Better to do it right.

Mud will crack when the tub expands/contracts with weight.

Mortar about the only thing that would work.

But not with americast since they say the heat can cause delamination later. --73.152.xx.xxx

Tub Install ? (by Frank [NJ]) Posted on: Jul 7, 2019 8:35 PM

Its a new tub --174.225.xxx.xxx

Tub Install ? (by Steve [MA]) Posted on: Jul 7, 2019 8:50 PM

You can get wire lath at any of the big box stores.

IMO the correct way to handle this is to remove the tub, make sure the plywood is properly secured to the floor joist, seal the plywood to prevent it from wicking water, add light weight mortar as needed to provide a good surface for the tub to site on.

If you aren't going to bother removing the tub, put some weight in the tub and use low expansion spray foam to fill the irregularities under the tub.


Tub Install ? (by RR78 [VA]) Posted on: Jul 8, 2019 12:52 PM

I remember researching these a few years ago. Seems by now someone should have a good replacement for cast iron.

Americast is trying but dont think they are there yet.

Usually you want to follow Manuf. instructions.

But it seems some people have more luck with a mortar bed.

But then other problems if you do.

I myself would try a steel tub before americast if I had to. At least have seen them last for years. Also would use only a top brand name.

Anything Plumbing is one of the few areas not to cut cost if you can.


Tub Install ? (by MikeA [TX]) Posted on: Jul 8, 2019 7:48 PM

I've used the low expanding (window and door) foam under several tubs with good results. Make sure you get it across the whole width and length of the shoe on the bottom of the tub so you have good weight distribution. Get a piece of small tubing and duct tape it onto the end of the can tube so you can get the distance you need. --50.26.xx.xxx

Tub Install ? (by MikeA [TX]) Posted on: Jul 8, 2019 7:50 PM

PS: If I'm not mistaken, low expanding foam is the manufacturers recommended install process on Americast. --50.26.xx.xxx

Tub Install ? (by Vee [OH]) Posted on: Jul 8, 2019 8:22 PM

Raise the tub with those fabric straps, pour in mortar and lower the tub gently, use levels on every maybe crooked position to insure the mortar will keep the tub level, it takes 2 days to cure. --76.188.xxx.xx

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