classi seal or mapegum and tape?

[shardy]

Hi all,
we are having another go at installing our shower tray.
the walls are quite out of square so the tiles wouldn't overlap the tray at the outer edges.
We are going to try cutting away the hardibacker at floor level on the left and right side, and sliding the tray under the wall.
If the tray is under the left and right wall at the corner by approx 5 mm then the gap between tray and walls at outer edges should only be about 5mm and the tiles will sit on the tray.

We would like to seal the joint also.
Can we use a product like Classi Seal? I'm thinking that if the tray is under the wall by 5 mm at the corner, the Classi Seal tape will buckle or stretch if we try to get the tape upstand to fix to wall, and the seal might fail.
An alternative would be to use the Mapei tape and gum. We've used this already but the seal failed at the outer edges because the gap we were trying to cover was 15mm. Is should work this time if the gap is a lot smaller
Hope this all makes sense, thanks in advance for any wisdom shared

 

[vinn]

The bottom course of tiles must overlap the tray. Hence, you must get the tray further back.
Remember that you cannot fix the drain position until the tray is finally fixed?
There's no need for the backer board to run down to the floor it can be cut say 6mm short of the tray. The silicone seal will provide the seal.
Sealing tapes and their like are a waste of time in my opinion - they can actually give you grief down the road.
The best trays have edge fins and the tile overlaps the fin.

Whats the history of you installing this or other trays?