Help!: New bathroom subfloor advice, pls...

[jimie]

Hi,
I'm just about to start redoing the bathroom floor and I would really appricate some feedback on what I prepose to do. So I dont make an expensive mistake!

The original subfloor is 22mm (equivalent) t&g floor boards. But these have been patched and repaired etc many times. So I am thinking of taking the whole lot up and replacing with 18mm exterior grade plywood.
I am also going to be installing a marmox showerlay tray in the corner of the room (20mm thick). I then plan to level out the dips etc in the floor (where the joists have settles since the house was built in 1930's) with a self leveling compound, then lay Ditra matting over the ply (this should bring the height of the floor to roughly the same as the showerlay tray).
Then I shall tile onto the matting and tray with large floor tiles 600mm x 300mm.
Does this sound like a workable plan, or have I missed something.....

I really value all the feedback and help I have been given on this forum. Many thanks

Jimie

[Alan.P]

Sounds about right to me, if your ripping up the old T & G floorboards you might want to put extra noggins in to make sure there's as little deflection as possible when the wbp goes down. Make sure to prime the underside and edges of the wbp before screwing it down, use an SBR primer NOT p.v.a.

[jimie]

Thanks Alan, for your advice and also for such a quick responce!

I had not even thought about priming the underneath and edges of the wbp!! As this bathroom is on the first floor and I hope the Ditra (or I may go for Durabase CI, both of which I hope to get from wetdecs) will ensure everywhere is waterproof, do I still need to prime the underneath and edges????? If so, just briefly what is the purpose and reason is.

And yes, I shall take your advice re noggins, good idea.
Thanks again.