I have a raised shower tray in our bathroom that is supported on wooden cross beams (not ideal I know), and there is a tiny bit of play at one end of the tray, meaning it flexes by about 2-3mm.

I’ve taken a look under the tray, and I can’t really get a hand in there to tap in some shims, so an alternative might be to spray in some expanding foam. I’ve been having a bit of a read online and many of the forums seem to suggest using a high density, low expansion foam – but I have no idea what I’m looking for, and google doesn’t seem to return much.

Can anyone in the trade recommend a product, or alternatively an alternative idea if this isn’t a good way to go? I don’t really want to take the whole shower tray apart as it means removing and reinstalling all the sealant etc.

Shower trays need to be on something solid,definitely not expanding foam. The ones that I have fitted have been laid on a 25mm cement base. If you can’t take it out can you put the packers under the wooden beams instead of between the beam and tray? In a years time when water starts coming through the ceiling you will know it didn’t work and the tray has cracked.