Installing Kohler cast iron tub (alcove) on plywood floor

So would this work?

1) Screw Durock directly to the studs (no vapor barrier behind it) from about 1/4" above the top tub flange (which is very small on these cast iron tubs, not nearly as big as the one in your blog) to about 1.5' from the ceiling (the tile will stop just a few inches above this).
2) Spread mortar on the Durock and Install Kerdi membrane over the Durock and Kerdi-band in the corners and along the tub flange and using Kerdi-Fix to attach the Kerd-band to the Durock
3) Seal around shower outlet, valve etc with the Kerdi
4) Install tile down to within about 1/8-3/16 of the tub and seal the tub/tile interface with caulk



Questions:

1) I assume I would use the special screws used Hardi makes for their backerboard?
2) Do I just bring the Kerdi membrane up over the drywall/Durock joint?
3) Do I need to do anything for the screws in the durock or joints between different pieces of Durock if I am sealing with the Kerdi membrane? Or sould I use thinset and tile (alkali resistant) mesh tape on the joints? Should I also do this for the corners?
4) I know you can score/snap the Durock, but what is the best way to cut holes in it?
5) would hardie backer or some other board be a better choice?

Yes, no shower. I was still planning on Kerdi on the drywall all the way up the wall to near where the tile ends.

johnfrwhipple said:

Mid Span blocking and missing wall studs for curtain rod on the right side of your tub.

Click to expand...

There is blocking up high for a curtain rod, but this is just a tub so I wasn't even sure if I would install a curtain rod. I have been thinking that I might prefer a sliding door which would require some blocking lower down as well so I am glad you mentioned that. i need to add some blocking for that.

It depends on whether this would ever become a shower how high you need to bring your waterproofing. IF the cbu joints will be covered with Kerdi, the Kerdi membrane will act as your reinforcement, and you do not need to band them separately. If the joints are not going to be covered with Kerdi, then yes, use the tape at all joints. Bond the Kerdi to the wall with thinset...use Kerdifix everywhere else you need to bond it to something (as in your tub).

But for the most part, the installation is the same for cbu and drywall if everything is covered with kerdi, right? The main difference being the screws that are used to attach it to the studs...right? With both you attach the Kerdi to the backer board with thinset and then tile.


Another issue I have been wondering about is how do you accomplish this to a tub that does not have a flange? My flange is small and runs almost to the front edge of the tub, but I know some tubs do not have a flange. How do do you attach the Kerdi-band to the tub then?

There are two reliable ways to waterproof that that I'm aware of (and probably others): most tub manufacturers offer an add-on tiling flange...basically, you'd adhere it to the tub deck with something like Kerdifix, then proceed as before; wrap Kerdiband onto the top of the tub deck, secure with Kerdifix (depending on the thickness of the tile would determine about how far you could wrap the membrane without it being seen). There are other waterproofing membranes, and they probably have similar options.