Best way to install shower tray

Hi
We have bought a low profile solid shower tray. The bottom is completely fl at. Our other one had ridges and I installed successfully using mastic to s tick it to the flat ply floor.
I used the same technique on this one but think that because the bottom is flat the mastic wouldn't spread evenly and net result was some give in the tray. I have now lifted it up again and wonder what the best option is to f it it?
One option might be to put many thin beads of mastic with spacing to help t he spread but wonder if I will get the same issue. The manufacturer has an alternative of putting sand and cement on top of the ply and fit the tray o n top (unclear whether this is a dry or wet mix and what thickness)
Any advice appreciated.
Thanks
Lee.
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On 22/05/2019 13:29, Lee Nowell wrote:

It's a wet mix, and a weak mortar. It works quite well.
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On 22/05/2019 14:34, GB wrote:

I'll second that.
SteveW
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Thanks very much both.
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On 22/05/2019 13:29, Lee Nowell wrote:

The stone resin ones normally suggest bedding onto a wetish mortar mix.
I normally mix up the mortar with some SBR as an add mixture. Trowel it onto the base, and get it approximately level at about 1/2" thick. Lay a couple of bits of plastic pipe across the mix, and drop the tray onto that. Slide into final position and then pull the pipes out to drop the tray in place (its easy to do heavy trays with access from only the front this way).
Put a level on it and tap level with a rubber hammer, then leave to set having made sure the drain hole is clear and unobstructed and ready for connection.
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John.
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On Wed, 22 May 2019 05:29:33 -0700 (PDT), Lee Nowell

My shower was installed on a bed of tile adhesive, which the fitter used because it was to hand. It's been in around 15 years now, with no sign of any movement or deterioration.
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On 23/05/2019 17:53, Peter Johnson wrote:

So long as it confirms to the shape of the bottom of the tray and gives good support, its probably not that critical what you use.
ISTR a friend of mine did it with bonding plaster since it was what was to hand... Not so keen on using something quite so absorbent myself, but in fairness it worked well enough.
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John.
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So I ended up using sand and cement. Any ideal how long it takes to set enough to stand on to tile?
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On 27/05/2019 13:09, Lee Nowell wrote:

Its a fairly well spread load, so a day or so should be plenty.
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