Mortar for bedding a shower tray - mix and thickness?

I'm going to be fitting a B&Q "stone" rectangular shower tray soon - what mortar mix and thickness should I use?
When I've installed shower bases before I've used silicone with one and mortar with the other - the silicone was much easier but this time the tray comes with instructions that say to use mortar and not to use silicone :-(
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Biggles@flies_undone.com wrote in

Read the installation instructions and follow them to the letter, otherwise the slightest deviation will invalidat any warranty.
Silicone is by far the easiest but if instuctions say morter then morter it must be and not one millimeter more or one millimetre less.
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On 02/03/2014 21:58, Heliotrope Smith wrote:

That was my intention, but the question is whether those with more experience than me would recommend any particular mix, thickness or additive.
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I put one of those trays in a few years back using a dry mortar mix. I took advice from the manufacturers who reiterated the need for a dry mix. The o nly advice on thickness was use whatever it needs to produce a flat and plu mb bed. The thickness I ended up with was about 12mm to 20mm due to the flo or running away to one end. Under 12mm and you will find it hard to keep th e dry mix as on contagious mass.
Richard
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Biggles@flies_undone.com wrote:

I did this job way back in 1998 and I believe that I used a 1:4 cement and sand mixed semi-dry and spread at an even thickness of around 15-20 mm. No addtives were used and the mix was wet enough to hold together when squeezed lightly in the hand with the base placed on the surface of the mix and lightly 'jiggled' to ensure an even contact.
Note that the bottom of my shower base has an inbuilt fall to the outlet and to maintain this, the mix was laid level as was the top edge of the shower base.
To ease the levelling up of an uneven timber floor, I cut a piece of good quality WBP 20 mm plywood the size of the base and laid it on top of the floor and bedded the shower base on this - and used the edge of the plywood as a fixing for the timber skirting that went around the base.
Hope this is of some help
Cash
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On 03/03/2014 11:46, Biggles@flies_undone.com wrote:

My trays al;so stated no silicone and use semi-dry .... so that is what I did ... why risk any warranty
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On 02/03/2014 20:44, Biggles@flies_undone.com wrote:

4:1 mixed pretty stiff .... paste more than cream
I put down 3 stone trays this way ... the big 1800 tray was real heavy to lower gently and evenly ....
Dry mix mortar is deff the way to do it.
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On 02/03/2014 20:44, Biggles@flies_undone.com wrote:

Thanks folks. I used 4:1 with a bit of plasticiser that was left over from an earlier job. It was slightly wetter than I would have liked (due to me not realising how wet the sand was) and ended-up about 15mm thick. When I did this a long time ago I used sharp sand and found it difficult to bed, with soft sand it was much easier.
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