The first thing to keep in mind is to protect the membrane fabric when working on it. It is not that it is extremely delicate, but it is sensitive to construction abuse. I cover it with cardboard as I work. The wear and tear does not affect the bonding of the tile, but my concern is if the membrane is punctured, it can affect the water-proofing.
The tile installation is not really different than any other installation. The membrane has become the substrate to tile over. I use un-modified thinset cement, in this case Ditr-set which has a smoother consistency than the standard thinset.
On this job I am installing 4x4 tumbled rust colored slate. The 4” size works well with the running of the water to the drain. Any larger would take a little more effort to pitch to the drain because larger tiles cannot taper to the pitch as well as smaller tiles. This floor a little more pitch than the normal handi-capped bath because of the rough sizes of the tumbled slate. If the material is uneven like the slate, it blocks the flow of the water with the highs and lows of the tile. So it requires more pitch. In a perfect world the 2x2 tiles work best.
I laid out the tile to have full pieces in the areas which are seen first and most frequently. I then measured off the wall for about six courses and then snapped a chalk line down the center of the room. This way if anyone looks at the floor from a distance and sights the lines of the tile, it prove to be perfectly straight. Once the main strip of tile has been installed, I use the 3,4,5 A-square (by the Hanson Tool Company) and square off the rest of the room. I used the ¼ inch notched trowel to spread the thinset. Spreading about 15 to 20 square feet at a time works best so the thinset does not set up. As each tile is put in, I give it a little slide to ensure a good contact with the cement.
Because the tile is natural stone, all of my cuts are done with a wet saw. This wet saw worked out great (Target Tool Company) because of its convenient size and good power.
Grouting and sealing – Before we grout the floor, we applied 2 coats of sealer to work as grout release. Normally one coat would be fine, but in this case the stone is porous and has a lot of cleft to it. If the grout had set up on the surface, it might have been very difficult to clean off. We used a color called light chocolate which well with the background of the tile. We spread the grout over the complete floor and then cleaned it off after it set up a little a half hour later. After we washed off the grout, we hit the tile with paper towel and a clean rag to remove any grout film.
The next day we cleaned the floor again with a good grout tile cleaner.
A few days later with gave the floor and grout another two coats of sealer (Miracle Sealants 511 Porous Plus). With most other products, one more coat would of have been fine.