Tiling Floor

[David Dudley]

Hi.

I recently removed all my old floorboards and replaced with 18mm Marine Ply.

This I thought was the best thing to do as advised in other posts on other forums and on here.
I have now seen contradictory advice.

The room is 1.6mx3m and most of the floorspace will be taken up by sink,basin and bath. It's a jack 'n Jill style room with a 1.6m length walkway between two opposite doors.

I have drilled the boards at 150mm centres directly to joists and put nuggins in accross the joins.
The thing that I didn't do was seal the edges and underneath. The bathroom is above a living room.

I plan to tank the walls of the shower/bath area.

There is no option of replacing the marine ply as it's now in place and would need cutting up to get out.

I was thinking of tanking the floor too. (Not a wetroom but to make it splashproof as I don't want water damage into living room below)
Would Ditra matting be recommended for this?
I have seen the un-coupling membrane? Is this designed specifically for this application? I've read about warping and obviously the cracking issues so any advice from where to go.

Any recomendations?

Thanks.

[kilty55]

hi david.....would you mind relling us what the other advice was?

you will get different opinions on installtions..and the one you have chose imo is good..the only thing i would add to what you have done is i would lay 6mm cement boards and tape the joints and i would tile directly to this

no need for tanking a floor or ditra imo for a bathroom but if you choose to go further then tanking is an option

[David Dudley]

The advice was mainly on this forum that ply isn't a good substrate to tile to. This floor seems pretty solid with no deflection.

I put noggins inbetween the joists for extra support and screwed at 150mm centres.
I'd rather not overboard with cement board - this would defeat the object of replacing the original floor in the first place, and I don't really want a step between the carpetted bedrooms and the tiled en-suite.

Using a decent flexible bagged adhesive such as Mapei - is this likely to be a problem or cause cracking?
As added security I was thinking of using Ditra CI+ for waterproofing, and to also help bridge the board joins.

[timeless john]

David - the object of replacing the floorboards would be to remove the number of joints and improve deflection. The 18mm marine plywood you have replaced them with should still give you 4mm in height to the original floor level of the floorboards. I'd fix a cement board at 6mm thick and tile directly to it or as you have asked - an uncoupling membrane with a flexible adhesive.

[Alan.P]

I would 'just' use a membrane, Dural, Ditra, this will allow for any lateral movement only, you say the floor is sound with no deflection, the membrane will act as waterproofing. No need to tank.