Gringo

Many thanks.

Silone would stick it down OK but wouldn't be very effective to allow levelling. Stone resin tray's must also fully supported underneath or they will crack.

Was that a stone resin tray or fibre glass? Stone resin is much heavier compared to FG.

Unfortunately it's a black, slate effect tray which "she who must be obeyed" picked. All manufacturer's generally recommend a weak concrete mix bed & have done for the last 20 years or so but, as I said, I've found this less than ideal. I'm thinking that, with the modern building materials now available, there must be a better option. I thought about using expanding foam but wondered if it was strong enough to carry the weight of our new, 120cm x 80cm stone resin tray tray which weighs in at about 30kg! After all the problems I've had with the last "tradesman's" efforts on DPM & plumbing, the very last I want is to have to pull it all up again!

Having moved to our bungalow around 3 years ago, I'm having to replace our ensuite shower tray due to damp issues. I decided to gut the whole room & start again & I've dug up most of the subfloor under the tray & found that the idiot who installed it 10 years ago just cut through & dug up the original DMP & didn't replace it with anything! This left the whole area under the tray exposed to damp ingress from the subsoil & moisture creeping through under the DPC in the external wall, the internal wall above the DPC was also extremely damp. This is obviously what was causing the smell & things going rusty which first made me aware there was obviously a problem. I've dug up most of the subfloor under the tray to let it dry out & will be reinstating a new DPM, connecting this to the wall external DPC before installing new drainage & a new stone resin tray. I've done this before a couple of times in the distant past but found bedding on a weak mix concrete, as per most tray manufacturers standard instructions, less than ideal TBH. I'm generally experienced in all aspects of building work including dry lining, plastering & tiling etc. & wondered if anyone can offer opinions/experience on bedding the new tray on either drywall adhesive or a waterproof tile adhesive as an alternative.