prob diagnosed, still need advice

[RCraig]

Some time ago you guys kindly helped me with a shower leak (into basement) problem. I could use a bit more of your helpful information.

My question is How is the front of a built-in tub normally supported? This tub has tiled walls on three sides. The tub is supported on the two long sides. Would there normally be some type of study support for the short front side as well? The reason for this question is:

The original problem turned out to occur only when weight (i.e. a person) was in the tub (cast iron). The weight causes the tub to descend a tiny bit. This then opens a tiny crack at the front end of the tub, where the shower head wall comes down and meets the tub. The crack is small, which is why it was missed for a long time, also, it is only there when there is weight in the tub.

I have not been able to figure out what to do about this. In the course of various opinions, one idea was: You need better support at the short front side of the tub. Like a vertical 2X4 that would sit on the main beam of the house (2 major beams run under this tub) and that would go up and support the front end of the tub.

Thanks if any of you guys have any thoughts. Ruth

[jadnashua]

A couple of things...the tub may not be sitting on the floor, or is not fully supported by the flanges, or the floor is not strong enough to hold the weight of the tub, water, and person without noticeable deflection. If the long sides are properly supported, the short sides probably won't add much. You could try cleaning the caulk out of the seam, fill the tub with water to cause it to open up the gap, then recaulk it. Leave the water in until it sets (at least overnight - some caulks don't actually fully cure for a week or more). My unprofessional opinion.

[RCraig]

The tub part of the tub is definitely not sitting on the floor. The bottom underside of the tub is maybe an inch or a bit less above where the surface of the floor is. The tub is supported on the long side that is against the wall, and on the other long side (where you get in and out) which sits on the floor.

So one option might be to slide something under the tub so that the tub itself would be sitting on something.

Another option was to try to support the front short side. This is where the leaking is occuring. However, from your advice, it doesn't seem that this would work very well.

I have recaulked as you suggest, with water in the tub, and it helps A LOT with the leaking. I am just worried in general that the tub may not be supported properly. I don't know how these types of built-in tubs are normally supported, on just the two long sides or on all four sides. Thanks very much for your advice. Ruth

[hj]

Are you sure it is a cast iron tub and not a steel one. I do not know of any cast iron tub that does not have support legs under it that rest on the floor, which means the bottom will not flex. And second, there is no person heavy enough to flex a cast iron tub even if it were not setting on the floor and was full of water.

[RCraig]

Very true. It may not be the tub itself that is flexing, but there may be some give in the support on the long wall side. When weight is in the tub, that side gives just a small amount. This opens up a small crack on the front short side, as the tub moves slightly down. The crack is right where the tub meets the front tiled wall, midway between the faucet and the long wall side.

What is worrying me is that if the supports on the long wall side are giving slightly, they may start giving more and more. I am trying to figure out some way to prevent that progression.

The tub is made out of black frying pan like material. Now that you mention it, I could put some kind of wood blocks under the tub, sitting on the beams below, since the tub doesn't have legs. Thanks very much for your thoughts. RUth