Lining floor before tiling

[rossbarclay]

Hi Guys,

Have done some reading online and spoek with a few tilers and builders about this, but inforamtion is so different I'd like to know fir srue what to.

I'm going to tile my en suite floor. The room is on the first floor. The floor is currently 22mm T+G. A suspended type floor on rafters if that makes sense. I'm told I need to line the floor before tiling, but what with? I'm told 6mm ply, but I read that it might warp. Then I'm told 12mm ply. But also read about cement board. The room is only about 2mx2m, and will be used for showering in. What is the best product to line the floor with?

Thanks
Ross

[royaloakcarpentry]

Even a 1.5M X.8M needs to be sorted for flex if there is too much in it.

Put a pint glass in the middle of the floor which is filled just below the full mark. Walk around normally and if the water is moving around there is too much movement.

If too much flex in the floor. Take up tongue and groove, add noggins between joists, 22mm flooring back down and cement backer board on top. Then tile.

If the water test is fine. Prep the floor correctly and tile or if a little unconfident, cement backer board and tile.

Remembering that cement boards need priming before tiling.

The weight of the tiles will take out a little flex but knowing when to risk it and when not to is something that comes with experience. The glass of water is a good fool proof way.

[Handyman in Sussex]

Hardie backer board is what we normally use, (or similar), stick it to existing T+G with tile adhesive and screw at 200mm centres in all directions and you're good to go.

Don't use ply, you'll only have to go over it with backer board. I only use ply to stabilise a stud wall against twisting and moving, but still put backer board over it before tiling. Even when primed with suitable primer tiles usually still fall off ply.

When you say the room will be used for showering in, do you mean with a tray and cubicle fitted or as a wet room? Big difference to the preperation for tiling if it is the latter..


All the best,
Jonty

[rossbarclay]

Just a tray and cubicle. Just thought I'd mention due to the mositure in the room.

What exactly is hardie backer board? And how thick should it be for lining the floor?

[royaloakcarpentry]

Hardi baker is one make of the cement tile backing boards.

Topps tiles and Nichols and Clarke do one with an insulated core.

I use 10mm on floors

[rossbarclay]

Sorry ROC, only seeing your first post now. What do you prime the cement board with? Just PVA and water? Do I prime the floor side and the tile side? What is this done for?

[royaloakcarpentry]

Never use PVA for priming before tiling.......it is a sealer and not a primer. PVA can reactivate when tiling commences and lead to bond failure. I.E the tiles fall off the wall.

There are manufacturer specific primers which are used. I always recommend that if a person is using X brand adhesive that the primer is X brand etc etc.

You prime the side which is being tiled onto. Essentially and in easy technical terms the primer forms a common layer between the tile and tiling background which aids in overall adhesion. You will love this bit.......the same as a sealer does lol. I think that is why some mumblies recommend PVA.

If you have adhesive under the backer board, you will also need to prime the T&G flooring first.

Always read instructions for primer as there are times when they need 2 coats and both applied in different directions.