Been looking at shower trays. All a bit new to me although I am handy enough at most things. One I like is very low and I am thinking about the water trap. The hole for the waste is at floor level so it seems to me that the waste water has to go below floorboard level or the tray needs lifting up at least the height of the trap.. Underfloor is not an option due to a) Not being able to get under the bath to the waste outlet and b) I would not be able to acheive the correct fall. Therefore, a frame needs to be made to raise the tray about 6 inches. Or am I better off buying a higher tray? How does a shower tray fasten to the floor?
Some sort of platform is a good way to go, if only because it gives you access to underneath the tray if anything goes wrong. Easy to make with a few lengths of 5" by 2" timber, with a rectangle of .75" WBP (waterproof, exterior grade) plywood on top.
A lot depends on what sort of tray you're after: ceramic? cheap'n nasty flexible acrylic? Stone-resin? Each has its own requirements for fitting. Try googling the uk.d-i-y archives at
You will have the same issue with most trays, so you may as get the one you want.
This is what worked for me, although it is not a definitive answer since I am sure there are variations that will work just as well. I also assume you are talking about a cast stone tray as well.
I would start by removing floor boards from directly under it (this will give you a little more "fiddle room" - if you really are adding six inches to the height you may get away without this. Then lay four (assuming it is a regular sized tray) joists of the right height evenly spaced and perpendicular to the existing joists. Screw down to the existing joists. Cut some 3/4" WBP ply to go on top. Now work out where the waste will go, and cut a hole in the ply big enough to allow you to get the waste through from the underside. You may also need to route away a little of the underside of the wood around the annulus of the hole to allow the compression nut that joins to the waste pipe to turn when it is all assembled.
Now do the plumbing of the waste, with the trap hanging on the end of the pipe, test fit the ply plinth and tray and ensure that the waste can be coupled to the tray (allow for the tray being approx a half inch higher than when just sitting on the ply as well). If it all fits nicely, then screw down ply to all of the joists of the plinth at regular intervals. Mix up some mortar for use as a bed, and lay a screed to approx 1/2" depth over the full area of the tray (except the waste hole!). Sit the tray on the mortar, level it off and tamp it down to ensure it is in contact with the mortar at all points and hence fully supported. Wait for it all to set before finally connecting up the waste with plenty of silicone sealant on all the mating surfaces of the waste. Finally seal round the sides between the wall and the tray with silicone. Then tile/panel etc down to the tray (so you final surface over hangs the edge of the tray). Leave a 5mm gap so that you have a good key for the final silicone seal.
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