Applied mortar to 18mm ply and shower tray, but it's moving?

[katloubee]

We applied the mortar mix an hour ago, we thought that when it settled a little it would stop moving, but when tapping one side of the shower tray, it kinda bounces, do you think we have to add more mortar in that area?

Thank you!!

 

[Burnerman]

Give it a chance to set.....! What kind of shower tray is it - a stone resin one?
John

 

[katloubee]

Thanks John

Yes it is stone resin, it's just bizarre as the ply doesn't move...we ripped it up once and put even more mortar on that area as we thought maybe there wasn't enough but it's still moving

It's the side against the wall (the longest side) and we haven't put down any sealant along the wall yet in case we have to pull it back up.

What do you think?

 

[Burnerman]

The whole idea of bedding a shower tray down is to ensure that the surface for the tray is nice and level, and has no high spots where the tray could possibly rock.
Therefore if the floor is good and flat anyway, a thick layer of silicone will do - it just acts as a cushion for the tray.
So - if I was using mortar, I'd put an even layer of mortar down, then drop the tray into place....giving it a bit of a shake to ensure it was settling. I'd check the edges to see that they were level.
I'd then scrape away any excess mortar for the edges (that has squeezed out) and then leave it be for at least 24 hours.
Its only quick set mortar that cures quicker than this......and that's not the best for a tray.
John