Best construction/prep method for bathroom floor?

[peterparker]

Hi there

I'm new to the forum so please bare with me. I am having an en suite shower room fully tiled with electrical ufh, it used to be a bedroom. At the moment there are just joists, the boards are shot so will be going in the bin. It's quite a large room ie 3.8m x 2.7m.

What I'd like to know is the best way to construct the floor from the joists up. Cost is not an issue, it has to be a perfect job which lasts.

I've read lots of historic posts and know that I need some combination of 18-25mm wbp ply, hardie backer, insulated board, ditra matting, latex, flexible adhesive etc.

I just need to know the exact order they go in etc.

Thanks in advance for your help

 

[Stef]

It's the way Hardi state it should be fitted.
When we say glue it effectively means mixing up tile adhesive & combing the floor with a 6mm notch trowel then laying the Hardi on top of this.
I mix my adhesive slightly wet as the cement board will sook moisture from the adhesive.
There is a grid pattern on the Hardi & you will see circles indents these are where to fix your screws, I use ScrewFix turbo golds 25mm.
It's pretty straight forward & gives a good solid surface to tile to.
They say standard adhesive to fix Hardi but I use a flexi as it sits better in my head as you are fixing to wood that moves slightly..

 

[peterparker]

Thanks Stef and sorry for the delay in replying.

Because of previous bad experiences and the cost of the tiles I want to belt and braces. So I'd like to tank(using paint) the wet areas and use ditra mat. So two more stupid questions please?

1) Do I tank the ply or the backer board??

2) I take it the ditra should be 'glued' to the backer board using the same flexible adhesive? But which sized trowel should be used?

All the help so far is really appreciated.

 

[Stef]

No need to tank the floor if your using Ditra (its waterproof) just make sure you use waterproof tape in all internal corners.
Tank the walls with a suitable tanking kit, I use Mapei aquadefence but there are a few on the market, Ardex sticks like the proverbial & is one of the best out there.
Ditra is only effective on lateral movement it will not help if there's any bounce in the floor.
Fix with either a 4mm or 6mm notch trowel.

 

[peterparker]

Thanks Stef.
I'll be using backer board on the walls in the wet areas. Do I just apply the tanking paint onto the backer board and then tile straight over it?

Cheers

 

[Stef]

If your using backerboard on the walls then get a waterproof board, something like Wedi, Marmox or Jackoboard if you can get it & then you just need to waterproof the joins & internals, save a lot of hassle.

 

[peterparker]

Hi Stef
The builder has actually already bought the hardie backer board. So shall I just cover it in tanking paint?

Thanks

 

[Stef]

If it's already been bought then yes just tank it out.

 

[peterparker]

Thanks Stef, your advice has been very helpful.