Cast Iron Tub Installation

Removed old steel tub and have temporarily installed drain.

Old tub was 30" x 60" new tub is 32" x 60". Installation is on a concrete slab which appears to be level. Old tub was resting on floor.

This is an alcove installation and the tub has a skirt.

A couple of questions: is there anything I should know before I slide this 350lbs tub into place? Walls are down to studs.

Also - getting ahead of myself - when installing the cement board "Durock" over the tub flang do I bring the board down far enough to cover tub flange and come into contact with and rest on the tub's flat surface? Also, is the smooth surface of the cemet board what you see after it's installed or is the rough surface left exposed?

Thanks, JM

If the instruction call for it, you may want or need to install a ledger board on the walls to support and keep level the edges.

THe rough side of the cbu is better to have out, but it doesn't really matter. Make sure to use the special screws, put a vapor barrier behind it and run it down over the tub tiling flange.

You don't want the cbu to bow out on the flange, so you can either notch the studs, or shim out the cbu so it just fits over the flange. Take it down to about 1/8-1/4" from the tub's horizontal ledge. You'll use caulk there, not grout. If you want to go without caulk, you can use something like Dilex from www.schluter.com. They make corner pieces too. If you use this, then you can avoid any caulk in the shower. Otherwise, you should caulk any changes of plane (i.e., corners, and at the tub, or in the wall to floor joint).

Lots of good points in jads post, so I will just summarize:

backer board should come down over flange, but stop about 1/4" above deck. Caulk with silicone. SHim studs if necessary so backer will be plumb. Then run tile down within 1/8" of deck. Then also caulk that gap.

flange

The flange on a cast iron tub is the thickness of the backer board so it is impossible to run it down over the flange without flaring it which would make a poor tile installation.