Shower waterproofing

[alyne]

Im building this shower cubicle in my new extension, walls are studwork, 12.5mm plasterboard and skimmed. The new stud partition visible will have cement board attached. The shower tray will be on risers so the waste can run above the floor.

I'm looking at the mapai waterproofing kit from toolstation (significantly cheaper than screwfix at the mo!).
I've got a question regarding the shower tray.
The PDF I've found online for the waterproofing kit says to rough up the edge of the shower tray and attach to the wall with the waterproofing tape. My plan was to waterproof the enclosure and floor / wall joins and THEN fit the shower tray, sealing it in with mastic. Then getting it tiled and then mastic the tile / shower tray join. The theory being that if the shower tray / wall join does weep slightly over time then the floor and few inches of wall below it are waterproofed.
I'll be doing the work myself, and getting a tiler (that I've used before) to tile the cubicle at the same time as the bath and sink splash backs.

Thoughts?

 

[23vc]

Your solution is better than not waterproofing it at all but why not get the tray in first and do it properly?
Fwiw last time I used the mapei kit i found it didn't bond well to the 7mm or so of tray, as opposed to an everbuild kit I used which seemed to work a lot better. Probably because I should have roughed up the tray edge better

 

[alyne]

That looks like a good kit - when I google it it comes up with aquaseal? I'm guessing that's the Same.
My main reason for looking at it my way is that the plasterboard doesn't quite come down to the floor and there's an expansion gap between the floorboards and wall, hence a largish (10mm?) gap which I wanted to seal.
With these kits is there any reason why I couldn't tank and seal the walls / floor and then fit the tray and tape / tank the joint?

 

[23vc]

No point sealing the floor, if water gets that far then the tanking has failed. Fit tray, silicone gaps around it to seal it to wall, tank the lot, going as far onto the tray as you can without it being seen after tiling. Tanking is flexible so allows for a bit of movement, if you did it the way you suggest it's more likely you could get a gap between tray and wall which would then let water through if/when the grout lets water through.

 

[foxhole]

I prefer shower panel , easy to fit and seal , seen too many tiled showers fail .