Help! Replacing Cast Iron in 90 Year old house

[BigDanRemodelMan]

I recently pulle dthe cast iron tub out of my mother in laws bathroom to find it had been set in a bed of mortar. 6 inch thick bed of uneven crumply mortar. She has to have this Kohler Cast Iron tub in it's place. What do I do? One guy said to build long mounds of rich cement and reset the new tub down on it and tap it to level. The tub weighs 316lbs. it is 60 inches wide and so is the bathroom. Getting it in position seems to be difficult enough, let alone setting it gently down on a bed of mortar. I am sure this has been done before, but I haven't.

[jadnashua]

A cast iron tub needs to be firmly supported underneath it - it should sit level and not rock. While a fiberglass, acrylic, or thin steel tub should be set in mortar to support the bottom, that is not necessary on a cast iron, although it can help with less than perfect floor. You need something underneath it so it sits level, and at the height you want, so a new stack of "mud" may be the easiest.

[Terry]

With cast iron tubs set within three walls,

I use a 2x4 on the back wall, set level.
On the apron side, I use a cedar shim to take the rock out.

[Yersmay]

I'm not a pro but it just so happens I installed my own cast iron tub just yesterday!! Here's what I learned -- first, in this instance, the instructions (it's a Kohler Villager) said not to hang the tub off its rim along the walls. It's supposed to sit on the four feet underneath. Once we got the tub situated in the alcove, we realized it wasn't level... so we used shims to level it up, checking along the back wall and along the two short walls. Get it as level as you can, but something tells me these cast iron tubs have oddities that make absolute perfect level kind of impossible. But we got really close! It was also important to measure from the front apron to the wall across to make sure the tub was sitting parallel, and square to the rest of the room. My walls are still open so I had an advantage with access for shoving mud underneath... So, if you have access it's good to shove mud underneath for added support. I used something called Cement All, Rapid Set. It's a form of cement grout that doesn't shrink as it dries. I mixed it stiff and made a mound of this stuff underneath, like a cement spine. Make sure you reach under and smush it so the cement is pressed up against the belly of the tub. It sets up in only 20 minutes, but that was more than enough time. That's it! It wasn't so bad.

[BigDanRemodelMan]

Last night I mixed two 80lb bags of higher quality mortar. (Messy Job) and through it on the old mortar bed. Shaped it to look somewhat like the bottom of the tub. 3 220lb guys lifted the 316lb tub and carried it into the bathroom. Put some2X4's from back wall to bathroom floor just above the mortar. Had to lift the non drain side way up to slip drain side into postion. Lowered entire tub on to 2X4's and took a breather. Talked about our plan and two guys leaned over and lifted tub up while third pulled 2X4's out. Lowered down onto wet mortar. Got in tub and shook around, checked for level, lifted straight up a couple times and shoveled a little mortar in there. The tub still rocked a little, but I hope with everything that that is because the mortar was wet. The imprint in the mortar looked great and even and supportive.

Thanks for everyone's advice!
Dan