Shower tray, alternative bedding advice

[Ed21]

Hi all, I've got a large 1700 x 800 stone shower tray that weighs a ton.
 
It will be fitted in an alcove against foam/cement board on three sides and will have a mira upstand
all round before trapping the tray on the edge with 12mm large tiles. 
The floor in front is being tiled upto the shower tray edge and the floor has been reinforced and extra
beams put in just in case. The whole lot has 18mm ply and is dead flat. 

Pinned on all 4 sides along with its own weight to say that this tray is going nowhere is an understatement. 

The underside of the tray is flat but rough (think stipple) so some very small high spots. 

 

It's possible I might (although not certain) that I'll be making some alterations where the tray may need
to come out and I'd like to avoid a permanent fix or one that if the tray was removed it may damage
tray. floor or wall.   

So the question is seeing that the only reason for having any bedding etc. would be to take away any high
spots on the stipple underside, would a foam type pad as used on laminate flooring etc. suffice instead? 

If not foam what about rubber etc? 

Any advice appreciated ?

Ed

[Ed21]

Just to add to the above as can't edit. 

What about thin polystyrene or PIR sheet etc. as well, would these be any good? 

 

Ed

 

[bassanclan]

If you lay it on something compressive it means it can move, if it means it can move then you have a potential water ingress.

 

You need to measure everything, decide where you want it and go for it, alternatively raise it either using the leg systems or a solid timber or block platform

[Ed21]

On 13/01/2022 at 15:32, bassanclan said:

If you lay it on something compressive it means it can move, if it means it can move then you have a potential water ingress.

 

You need to measure everything, decide where you want it and go for it, alternatively raise it either using the leg systems or a solid timber or block platform

 

Just done a trial run using some 5mm laminate foam underlay. The compression on the high spots is down to under 1mm
and all the voids are fully filled. The tray is now fully grounded with no further compression possible, it's created a solid bed
across the underside of the whole tray. 

If anybody has any opinion as to why this is not a good idea, can you please let me know before I make it permanent. 
 

Cheers all = Ed 

[TonyT]

It’s doesn’t follow the manufacturers installation instructions?

[Faz]

Best to bed trays on a layer of mortar. It is not necessarily the issue of movement and leakage but the actual tray cracking over time with any small flex. The underlay will not prevent fatigue through repeated tiny movement.

[bassanclan]

There are millions of shower trays installed in the uk, only one is installed on a piece of laminate flooring underlay, maybe everyone else is wrong!

 

The tray really needs to be rock solid which means bonded to the surface below either with mortar or tile adhesive.

 

You have probably paid a couple of hundred pounds or more for the tray, but the manufacturer warranty won't apply if its not installed according to their instructions.

 

Make a decision about if you need to move the tray and then fix it in its permanent position properly