Flexing wet room floor

[homeowner77]

The mosiac tiles near to the drainage area are flexing quite a bit. We can see the drain moving up and down too. The grouting is cracked in places.

What's going on?
Is there not enough support underneath the shower tray?

Any help much appreciated.

 

[Dave]

What type of wet tray is it and what size of mosaics ?

 

[homeowner77]

It is a foam tray (sorry no more details than that) and the individual mosaics are 2.5cm sq.
I've just been reading that they should be 5cm sq....is this correct? Could this be making the area around the drain too flexible and causing the cracks?

 

[Slippery]

How long has it been down?

 

[homeowner77]

It's been down around 6 months

 

[Slippery]

Possibly the drain holes in the waste filled with adhesive, the water flows to the drain under the tiles but can't escape through the waste.

 

[Dave]

The issue with small mosaics on a foam tray is point loading, the tray is at it thinest towards the drain. So larger mosaics prevent crushing of the tray. But the drain itself should not be moving. The issue could be installation error as the drain needs support underneath to prevent collapsing.