Fitting a stone resin shower tray on plywood

[DIY Bobster]

@George 3G I know this is an old post, but it looks like you installed the same tray as me (Merlyn Level 25) and I have a few questions about it please.

 

Firstly, I am assuming you went with using flexible tile adhesive to stick the tray to the ply. There seems to be a bit of a mixed opinion on this method vs "Sand and Cement", which is what my instructions advise. From what I can gather, the disadvantage of using tile adhesive is that it actually sticks the tray down, which means if the floor or tray flexes, then the tray will flex too and potentially create hairline cracks. Have you had any issue so far? Also, did you try the sand/cement method first? I did, and it didn't really work. I expected the mortar mix to spread out under the weight of the tray, forming a prefect imprint/cast of the underside of the tray. However, when I did it the result looked more like some squished dabs of sand cement. I am 99.9% sure this is an error with the way I have made up the sand/cement mix (possibly not runny enough, or not enough plasticiser?), but wondered if you had a go using this method before resorting to tile adhesive.

 

Lastly, did your tray have any issues with the level test on the 3mm spacers? The first tray I received had to be sent back because it failed the "rocker" test on the spacers (only marginally). The second tray passed the rocker test when I received it (just, there was zero clearance in the middle of the tray, but the level did not rock). But when I tried the rocker test when it was bedded on sand/cement, there was a very pronounced rock. Merlyn then asked me to test again with the tray off the sand/cement and on the wooden blocks, it now has a 1mm rock on the long edge.  I have passed this back to Merlyn but am now wondering if this issue is inherent with this kind of tray, or whether I have been unlucky.

 

Thanks :)