Just a little clarification required on my plan of attack

[angrypirate]

Hi guys, I just need some input from you guys regarding my course of action on a small bathroom floor, I've searched and read so many threads on hardie v ditra I'm more confused than before I started reading as there's so much info .

Story so far...

Bathroom floor 2.4 x 1.7m
8x2 joists ( I sistered the joists with 6x2's to level the floor and remove the slight bounce).
Joists spacing was 450mm
I put noggins in every 300mm
I replaced old 'T&G planks' with 18mm WBP (SBR Underbeath and edges/notches), screwed every 150mm where possible. Also glued with D4 Polyurethane glue.

The floor is 100 times better now, even the plumber commented on how sturdy it was, and he doesn't give praise often

I was going to put down 6mm hardie, but it seems they won't add any more rigidity to the floor.

So here's my queries.

I'm thinking Ditra for ease of installation and reduction in step onto landing using Ultra Tile Sp with 3mm square trowel to bed the ditra then 10mm square to Install the 15x90 porcelains.

Instarmac say the addy is fine, but I can't see it as a recommended on Schluter site.

So do you think the plan of action is good one?
Maybe upgrade to a 4mm to bed the matting?
Use Mapei VS90 to bond the matting?
Do I need to prime the Ply for Ditra?

 

[Tiler Durden]

I’d use Hardiebacker on top of the ply. it’s a better material to tile onto and is not only glued to the ply but mechanically fixed. It’s never going to come up that way