Planning a level access shower

[Al Getaroundtuit]

Hello all. Newbie here. I'm new to the forum so go easy on me!
I'm looking for advice, please, having trawled the net and ended up here.
So far I've had conflicting advice about the best way to create my en suite shower room in the new extension/bedroom (1st floor). Room is approx 1.8m x 2.0m, with 22mm t&g chipboard over pretty hefty 195mm x 47mm joists (1.8m span).
Ideally I would like a level access shower with tiles throughout and a glass screen as opposed to an enclosure.
I was going to proceed as follows but now I'm not so sure:
Remove floor boards under tray, batten joists, 18mm marine ply to joist level. Prime floor (SBR?). Fit Prowarm 30mm former, fit 6mm Prowarm boards to rest. Tape joints, corners etc & paint with sealer. Fit ufh heat mats to all but shower, level compound, tile (mosaics to tray area).
However, having read some comments re Prowarm boards, I'm now worried about compression and thinking maybe Hardiebacker is better?
I'm using 12mm Hardiebacker to shower area walls.
I've seen the Tuff-form type trays but my joist centres are 600mm and the tray would be 800mm so would overhang the joists. Not sure how to overcome this as all of the YouTube clips seem to show exact fit between joists. Also, if I use a 22mm tray then the floor level will be higher than the tray once I've boarded over the chipboard?
As you can tell, I find it all confusing. Please advise. Ta.

 

[Flintstone]

Ditch the Hardie and use the insulation boards on walls and floor. Thicker on the walls depending on solid or stud?

 

[Al Getaroundtuit]

Thanks for the reply. The partition walls are studwork and the outer wall is blockwork. Wasn't sure if I needed to plaster the outer walls or just board them? Is it true that the insulation type boards will squash on the floor especially the tile former if its this type and used with mosaic tiles rather than large format?

 

[WetSaw]

Minimum tile size depends on the brand of board you intend to use.

 

[Flintstone]

50mm is the minimum tile size for those boards on the floor

 

[Flintstone]

The tray should be fitted on a platform created at joist level so size doesn't matter.

 

[Al Getaroundtuit]

The tiles we have bought for the floor and walls are from a well known DIY outlet and called Aspen Carbon Grey/ Aspen Silver Grey 598 x 298mm.
The ones I was considering for the shower area are a matching mosaic type which are 300 x 300, made of 6 x 6 small tiles.

 

[Al Getaroundtuit]

What I was worried about was point loading on the tray ie will it "crush" with the mosaic tiles as opposed to larger tiles which I'd have to cut with "envelope?" cuts

 

[Al Getaroundtuit]

So can I board directly onto the blockwork or would I need to plaster/board it first? Thanks.

 

[One Day]

As above - hardibacker in a wet area is a waste of time and a bad idea.
Use a waterproof board and save some headache.
Consider other tray types - Orbry / PCS / Marmox / Wedi / Schluter.
There are many options and all the lightweight ones can be cut down to a fair degree to suit.