I have a bath tub installed in my basement. The tub's front and back long sides are leveled. but not left and right side. The tub is about 1/4" off towards back from both the sides. I don't see any drain problem.

Initially, the plumber used mortar to install & level the bath tub. Actually the floor was not 100% leveled, but he left the tub out of level from sides, and now the bath tub is set.

I am going to install this 4-piece tub surround myself, and I just noticed this problem now. The tub's manufacture mentioned the tub should be leveled perfectly.

Would I be able to level the bath tub, and if so, how?

tub in bare framing with notes showing which corners are out of level

  • If there is no problem to drain, or collecting water, I would save myself the trouble. You can, but obviously, you need to lift up the tub and level the grout pads below. THen you might run into problems that the edge is either sets too high or too low.
    – r13
    Sep 20, 2021 at 1:10
  • If I understand your labeling correctly, the (short) ends of the tub have sagged, but the (long) sides are level? Since it appears that you still have the walls open, I'd think you'd need to somehow jack those ends up. I'm guessing it's a plastic (of some sort) not metal tub which is why it was able to flex like that. Why did the plumber leave the tub unlevel and how is it now "set" without having been first leveled?
    – FreeMan
    Sep 20, 2021 at 14:53

2 Answers 2


I'd try to raise the back edge 1/4" to level the tub and then pack in mortar underneath both sides as far as I could get it in. Possibly install a few shim strips to fill the gap. Those surrounding tile stalls really do need a level tub or you'll need to shim the wall.

  • You raise from front it would be a gap of 1/4+1/4. why do you want to raise from front ?
    – user141303
    Sep 20, 2021 at 15:42
  • @user141303 My bad! I thought you were implying that the tub had to be lowered a 1/4", not that it was down 1/4". I edited my answer.
    – JACK
    Sep 20, 2021 at 15:51
  • I just realized you and I are sort of proposing the same solution (raise & pack), but it seems you're more worried about the tilt, and I am more worried about the gap. Let's see what feedback the OP provides from the situation.
    – P2000
    Sep 21, 2021 at 16:00
  • @P2000 My thoughts are if you fix the tilt, then the gap is solved. It's probably a cast iron tub so the tub rim probably won't bend. Cool to see what happens.
    – JACK
    Sep 21, 2021 at 16:49

In terms of water ingress into the stud space, the tub surround will be 1/4in high on the sides of the tub, but the lip of the tub stands high enough to lip behind the surround. You can check this by measuring the height of the tub's lip and comparing to the "droop" of the tub.

However, you might have water standing at the lip if the current slope prevents it from flowing into the tub. Assuming this tub is also used for showering, you'll have build-up of soap residues as water accumulates and evaporates while standing in the corner.

To caulk the seam you could aim for the tight gap behind the surround where it touches the tub lip, rather than try to fill the entire 1/4in gap. First do a dry install of the surround, then for a final install first apply caulking to the tub's lip, rather than applying it after the install. Ensuring you have the upper 1/2in or so of the lip caulked.

Alternatively, you could try lifting the sides of tub by installing a piece of 1x or 2x support lumber. The length of it should be about the width of the tub. Carefully jack the tub ends up with some vertical lumber, fastening the support lumber to the studs. Let the tub's rim bend a bit but do not lift the tub off its base. This could compensate a good portion of the 1/4in drop, but possibly not all of it.

Be careful not to put too much upward pressure on the tub rim so as to lift the tub and make theses supports the hanging points of the tub; you still want the cemented bottom to be the base and carry the bathers'/bather's weight.

You could then add a bit more cement to the base of the tub around the head and foot end, to provide support for the minimal lift that may have occurred here. Simply slap the cement against the tub's underside & floor.

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