Tanks Bob for explanation.
I have some more questions.
As I mentioned before we are planning on using Porcelanosa large format
rectified tile.
Tile is 12" x 35" x 1/2" - pretty big. I got myself used but in great shape Rubi TX-900N cutter for long cuts, and I will borrow nice tile saw from a relative for smaller cuts. Tile manufacturer suggests using modified thinset, but that will not work over Kerdi. I will have to use unmodified when tiling over Kerdi.
Q1: Tub and surrounding wall (top of the drawing). There is no shower in that location, just dedicated jacuzzi tub. I will install 1/2" drywall on the wall. 2x4 studs run at least 16" O.C. and more frequent in some spots. Wall height is 8' floor to the ceiling. Top edge of the tub is approximately 2' off the floor. I want to use Kerdi on walls surrounding bath and bath surround (bench/skirt). Kerdi will give me approximately 3' from edge of the tub and up the wall. Which still leaves about 3' of just plain drywall.
I think I have 2 options there:- Overkill and run another roll of Kerdi up the wall to the ceiling. Pros: same level of substrate. Cons: Waste of Kerdi, since no water will be near.
- Install CBU for top 3' above Kerdi. Pros: good substrate for tile. Cons: Dealing with CBU and possilbe thickness difference.
Any other option I have here?
Q2: Across the room there is a 9' 1" wall (bottom of the drawing). 8' floor to ceiling. We want to tile entire wall with same large format tile. Left bottom corner will have toilet installed and to the right there will be a wide vanity hanged on the wall with 2 sinks and mirrors above. 2x4 studs run at least 16" O.C. and a lot more often around the vanity. Some of them sistered together.
What do I use to cover the wall there and then tile over that substrate? Do I use CBU and modified thinset there? Can I just tile over drywall in this situation and maybe use some Kerdi just over the vanity (not sure if its a good idea)?
I'm ready to make a trip to local supplier and need to get idea how much drywall and/or CBU I need to buy. Also if its CBU what kind and how thick?
