Tile – 2nd floor bath remodel. Concrete under tile. What do I have to remove

I have a pier-and-beam house, and the instructions are pretty much correct.

Tile will crack eventually when placed over pier-and-beam because of two related issues:

1. Floor joists often aren't on 12- or 16-inch centers, so they allow too much "give" when you step on the floor between the joists.

2. The piers are settling independently of one another based on soil conditions, and even fractional-inch movement is enough to crack grout lines over time.

So, if you really want tile, I would suggest removing the existing linoleum, then do the following:

1. Ensure that the subfloor is as level as possible before you begini. This is a lot better than to discover later that you need to shim your subfloor, use self-leveling compound, etc. for the tile to lay flat.
2. Lay a first layer of 3/4" plywood (or leave the one you have if it is in good condition and screwed down well).
3. Install a second layer of either 3/4" plywood or cement board going the other direction, so any movement at the first-layer joints is distributed across the second layer. Be sure to use long wood screws that go through both layers and back into the joists.
4. Install a decoupling membrane such as DITRA over the subfloor.
5. Install the tile.

Backer needs to go up at least 5 feet and extend a couple inches out a tub surround and used in all parts of a shower. It only needs to be in the wet areas.

For tub surrounds I normally put two horizontal pieces of backer board (goes 6 feet over tub top). Tubs are usually 5 feet in the US and backer is sold in 3x5 pieces. I then put one piece vertically on each side (going out a few inches) plus a partial piece to meet the 6 foot back wall. So I need to buy 5 pieces for a typical tub surround.

You meet your drywall from above and side from there. Just a normal join. I use mortar to fill backer to backer joins and drywall mud for back to drywall pieces. I really really suggest tiling over your backer to drywall joins too since 1/2" backer isn't as thick as 1/2" drywall. The tile coverage makes it easier and looks better. You don't need to backer behind your toilet or anything like that.

Edit - I would also note that I almost always have to add 2x4s to allow me to attach the side backer boards and allow for a firm place for drywall to meet. If everything in the room is "down" then I would actually put up 2x4 after backer - so I can make sure it meets in the middle with no cut. Cutting a 1/2 inch of backer board isn't worth the time!

Also I like a 2x4 right outside my tub external too - these are there a lot of time but not always. Obviously I would have to put this in pre-backer install. This is more for attaching your drywall.