Tile T&G flooring

[Gareth1]

Hi all,

I'm renovating my bathroom. I was going for lino on the floor but I've changed my mind and want to tile it. I'm confused about what's acceptable.

The floor is 18mm T&G floorboards. The bath is in already so I can't really go back to joists and put down 25mm ply. I also want to avoid a large step up into the room.

The room is small - the floor area I want to tile is about 2 sqm. I can put a full glass of water in the middle of the room and walk around it with none spilling. If jump on the floor then small ripples but none spills. I'm 16 stone. The floor is built from 8x2" joists (and one 8x3") and is supported by the end wall of the bathroom. The tiles I want are 12" x 12" travertine.

Would this approach be OK?
1. sand and scrape the floor clean.
2. prime with two coats of SBR diluted 3:1 with water going in different directions.
3. stick 6mm hardiebacker down with SPF using 6mm square notched trowel, screw while adhesive is wet and scrim the joints.
4. tile over with single part S2 adhesive (BAL fastflex).
5. Grout with same grout as wall tiles (BAL micromax)

Cheers
Gareth