Laying a shower tray

[Eddman]

So i have a large(ish) shower tray and a floor that is not level! there is roughly a 20mm fall over the length of the 1400mm tray.

My idea is to build up in steps the floor with layers of 3mm plywood so that a spirit level will sit level when placed across the build-up.

Then, i believe i need a cement bed. Is this to 'stick' the shower tray down so it doesn't move - or is it just to provide support to the whole ares of the tray? Then i silicone around the 2 edges that meet the walls - does this 'stick' the tray in place?

i am not sure what to do with the front edge that will obviously have a 20mm gap from bottom of the shower tray to the floor level. I was hoping to be able to get a plastic trim and cut the bottom edge so it follows the floor slope and provides a level top edge.

i have already laid the tray on a bed of drywall adhesive and after the 24 hour period i tried to lift the tray to make sure it was stuck down but it came up really easily - hence my question about whether the cement bed is to actually hold the tray down or just make sure the the entire shower 'pan' is supported.

i hope this all makes sense and thanks to all who reply

 

[Baths'N'Gas]

Stiff mix of flexible floor tile adhesive (rapid set)

Will be set in a couple of hours

 

[Eddman]

Thanks, does that hold the tray in place? Is it that that 'glues' the tray down and stops it from moving?

 

[Baths'N'Gas]

our company fit at least 3 shower trays a week, every one has been put on a bed of rapid set over the last 6 years and we've not had a problem with any

If the tray is going on floorboards, I would recommend screwing 9mm ply (minimum) down using a screw every 6 inch where the tray is going

 

[Hot&Cold]

So i have a large(ish) shower tray

Does it come with fitting instructions ? some don't require a sand & cement base but some do. Its to do with the tray construction they do vary by maker.

 

[Eddman]

It did not come with fitting instructions

 

[Hot&Cold]

It did not come with fitting instructions

Did you buy it on the internet,unseen ?

 

[Eddman]

i did, it was from Victoria Plumb, i have since spoken to them and they said to lay a cement bed.

I took BathsNGas advice and bought some floor tile adhesive ( http://diy.com/departments/mapei-large-format-powder-floor-tile-adhesive-grey-20kg/38143_BQ.prd ) and laid that onto a build up of 5mm plywood (laid in steps to achieve the required level). I have since put the shower tray down but did not get around to any further work yesterday - so although i got rapid set stuff, i have left it over night and will not be looking into doing any more work on the shower enclosure until this evening - so it will have been 24 hours since i laid the rapid set adhesive!

I had previously used driwall adhesive but after the 24 hours, i could easily lift the tray up - it had not glued it down at all. Is this what is supposed to happen? is the cement/adhesive supposed to grip the tray down to the floor - or just keep it supported? I wondered whether i scrimped on the driwall adhesive and didn't put enough down and that is why it did not hold.

i am still a little confused (bearing in mind my previous attempt) - does the cement/mortar/adhesive bed (10mm seems to be the suggested but with this stuff i went a little thicker!) actually glue the tray to the floor AND support throughout the base OR is it just a supoort and the tray will be glued by the silicone around the preimeter (2 sides in my case)?

 

[copea]

The tile adhesive both supports and fixes the tray in position.
The silicone is to prevent water seeping down between the wall/beneath the tiles and the tray. It doesn't have any structural properties as such.

 

[Eddman]

so i presume that when i used the driwall adhesive, i just didn't put enough down - or it was too solid a mix to allow it to take with the underside of the tray.

i put loads of the tile adhesive down - i used a 20kg bag with 3.5l of water for a shower tray that is 1390x900.

 

[Eddman]

So.....(big deep breath!)...next problem. I have cut a hole in the floorboards for the waste but where this is, there is no support for the tray. I was thinking of trying to get a piece of ply bove the pipes and fill the gap. This is tricky as the tray is now stuck down and the only access is through the waste hole (90mm dia). I was thinking of trying to get some expanding foam in there - easy as through the bendy straw applicator. Will it cure rigid/strong enough to support the tray? The other option is to try and get a full bed of tile adhesive in there. This will be much harder to do due to limited access!

You can see the underside of the tray in the photo and the hot/cold feed pipes. I want to cover the pipes and void with ply, then fill the gap with expanding foam or adhesive slurry....

Thanks again for all input