Unconventional tub install (aren't they all?)

[BeckyK]

We set out to remove old bathtub and replace with new. Ah, ha, ha. Now down to studs. So, decided we'd splurge on corner whirlpool and separate shower. Bought drop-in Kohler whirlpool because it's the only one the right size with pump in right place we could afford. Installing in a 3-wall alcove set-up. Bought Kohler bead kit to install tile flange. Oh, and just lost our semi-professional "helper" to a new girlfriend, so husband and I, decent DIYers, are winging it at the moment.

Greenboard already installed on new studs, new insulation and vapor barrier. I know, I asked for cement board. "Helper" didn't listen. Since tub only and no children, maybe OK? Yeah, I know, should have been installed AFTER the tub. I didn't do it.

We're a bit stymied on installation now.

a) drain purchased specifically for this tub is 3/4" too long. We're guessing to accommodate mortar bed or supports as shown in installation instructions. Could we just place the tub on a 3/4" or 1" sheet of plywood so don't have to try to glue shims to bottom supports? House is a modular and bathtub literally sits above an I-beam, so plenty of support.

b) since greenboard already in, can we get away with having tile flange on top? I've asked for specific info from a tile forum, but happy to have more input.

c) do we have to secure the tub to the floor somehow? How's it going anywhere with 3 walls? Really not comfortable trying mortar.

d) should we drill holes through the rim underneath along the back two walls to screw it to the studs since we don't have a standard tile flange to secure with?

e) we won't have a standard deck. Just one small corner where the tub meets the new wall. When we frame the front edge, we'd like it to be flush with the rim of the tub. BUT, I also want to be able to sit on the front edge to swing my legs in and out of the tub. Seems like we need to support that front edge underneath somehow? Typically just the rim rests on a deck with no weight I believe. Right now, totally unsecured, if you push on the front lip, the whole tub tilts.

f) should we throw in the towel and call a plumber? contractor?

Your thoughts appreciated.

 

[hj]

you need to support ALL the "edges with "pony walls" under them. The rear edges need "backing" boards under them. You ALWAYS cut the drain to fit the tub, even when it is designed for that tub.

 

[Sponsor]

 

[BeckyK]

you need to support ALL the "edges with "pony walls" under them. The rear edges need "backing" boards under them. You ALWAYS cut the drain to fit the tub, even when it is designed for that tub.

Thank you. We'd come to pretty much the same conclusion. Nice to have confirmation.

 

[hj]

However, without at least a small ledge around the tub, you may have difficulty tiling up to the flange and keeping it from separating over time.

 

[Terry]

hj is right. Support is needed all the way around. And if the tub doesn't sit flat to the floor after setting it down on the support, you may want to shim the bottom of the tub. We normally do this with small piles of mortar mix that squish out to conform. If none is needed and it's has support, all the better. Sometimes construction adhesive is also used if the fit is very close.
The drain is normally fitting to the tub first, then you can remove it, set in in place with the p-trap, and then drop the tub back down and thread things back up.
The tile ledge goes behind whatever backer you have. Remove what you need and start over.

 

[Cacher_Chick]

I would take it as a fact of life that the tub walls WILL get wet, particularly the bottom few inches over the tub. I would replace the greenboard, because it is no better that regular drywall and is not going to hold up over time unless the tub is never used. No matter what material you use, I would apply a topical waterproofing to AT LEAST the 12" of the wall above the tub flange, and then make sure to do a supreme job of sealing the joint with silicone caulk when the rest of the work is complete.

If you are flipping the house, hack away. If you plan to live there, do the best work you can possibly do. A tub job should be good for 30 years or more when done correctly.

 

[BeckyK]

Thank you all for the advice. We have removed the greenboard. Installed ledgers around 3 walls. Will be building 2 x 4 support wall with narrow deck for front and remaining side. Tub is a Kohler #1154 corner whirlpool drop-in model. Will use Kohler bead kit to attach rubber tile flange. Will run cement board over flange. Will waterproof.

Question now is: tub has a base with feet. Floor is level. Dry run - tub sits perfectly level. Kohler instructions give both mortar or adhesive as options. Since tub and floor are level, I lean toward adhesive. However, since tile flange is rubber and NOT attached to wall, the tub is basically a drop-in and could, I suppose, potentially shift, which would, possibly rip my tile off the wall?

To mortar or not to mortar? If yes, can mortar go on top of new vinyl?

Thanks much.

 

[Cacher_Chick]

Normally the finished floor is installed last, butting it up against the tub surround.

I have never seen construction adhesive recommended by a tub manufacturer.
I would lay down a sheet of visqueen and put down the mortar piles on top of that.

 

[Terry]

I have done both the mortar when things needed support, and adhesive when things were flat and fitted up well.
Some Sterling tubs come with a felt pad to lay under the tub which works when everything is level.

 

[BeckyK]

Thanks Terry. Appreciate the expertise.