The instructions say install shower tray on 20mm plywood (to ensure flat).
But is the outer edge of tray supposed to rest on the very edge of the plywood. Seems a bit dodgy to me ??
Any suggestions,as i need to raise tray by about 50mm, as waste falls bang on a ceiling joist.
Its either severly notch the joist and then add a strengthening beam alongside it. Or raise the tray up.
What sort of tray is it?
Stone resin ones usually need a ply base and then bedding on a thin screed of mortar.
Why?
Screw some 2x2 across the joists, ply on top, tray on top of that.
Unless you particularly need to avoid having a small step up into the tray, then raising it is easier than messing with the joists.
I have a stone resin one fitted onto a piece of 20mm external grade plywood as per instructions - which also said bed the tray on 15mm of cement screed on top of the plywood to ensure a flat bearing surface.
In my case, the ply base is the same size as the shower base and I used the edge of this to fix 3" skirting to - this helps to hold the base against two walls securely.
I drilled the centre of the trimmed joist in the way - again in my case, the joists are running the 'right way' for the waste pipe.
If all your joists are running the 'wrong way', it may be better to raise the shower base as per John Rumm's post.
Cash
It just seems a bit dodgy as all the weight of the shower cubicle glass is resting upon an edge that is only just supported by the edge of the plywood. Or maybe I am bit over cautious.
My shower tray has a large radius, so I could not use timber skirting, maybe some UPVC cladding of some sort.
I did wonder what stops the tray from moving. Apart from its own weight.
After you drilled the centre of the joist, did you add any strengthening timber to that joist ?
Its hard to decide which is the right or wrong way, I suppose the waste pipe comes out of the trap at 90 deg to the joist. It then will have a 90 deg bend within the joist space, to come out of the tray area.
I have tried to find the smallest in height shower trap, so I do not have to notch the joist too much. The smallest I have come up with is using a low level bath trap, ie a Marley WSB4W. Any suggestions ??
Yes stone resin - but if installing it onto a wooden joist/floorboard bathroom. The thin screed will just breakup over the years, with movement of the old timbers.
I think from my engineering background I maybe over cautious. All the weight of a lot of glass is supported ultimately on the very edge of some plywood.
I bought a low level tray and it seems a pity to have to raise it up. But it all hinges on wether I can get the waste trap in.
I had a similar proplem a few years ago to get a 110mm soil pipe through a joist, which would have only left 50 or 60mm of joist remaining. I found some heavy steel plates about 6mm thick, big enough to span the pipe area with plenty of space either side. I welded some 50x50x6mm angle iron along one edge - so that this sat along the ceiling when in place. I then cut out a pipe sized 'U' shape in the middle. I made another (but mirrored) one for the other side of the joist. I bolted these either side of the joist with long bolts and washers, then cut the wood from the 'U' area of joist exposed with the plates in place. By doing this method I added strength to the joist before weaking it, so no risk of anything moving. Once done I tested it by jumping up and down on the cutout area... no spring at all :)
is it not possible to turn the shower tray 90 degrees thus missing the joist?
bathroom. The thin screed will just breakup over the
The ply is there to maintain a firm base for the mortar - for a typical tray it will be supported on 4 joists (or cross joists over joists), and if you use 3/4" ply will be very rigid. The mortar is there to spread the load so that there are no high pressure points on the tray or any rocking rocking etc. IME it does not break up, but even if did get the occasional crack etc it would still do its job.
of a lot of glass is supported ultimately on the
Well supported ply, with an evenly distributed load over it. If you were really worried you could add noggings to support the free edges, but personally I have never bothered.
all hinges on wether I can get the waste trap in.
Yup, much depends on the direction of the joists etc. You can always cut one and put a stringer across the pair either side to support the cut end.
resting upon an edge that is only just
some UPVC cladding of some sort.
Radius as in rounded corners, or as in a quadrant tray?
I have done one of the quadrants before, and got quite a nice skirting effect by cutting some of the spare floor tiles into 3" wide strips, and tiling round the arc, it made the step look like an extension of the floor.
Mortar - or you can get away with a bag of bonding plaster. The former is better since it does not absorb water if it gets wet.
comes out of the trap at 90 deg to the
the tray area.
Remember you can also rotate the tray (assuming its square) to reposition the waste.
notch the joist too much. The smallest I
You can get shallow shower traps... although one gottcha is if the shower tray is 3/4" and you have a mortar bed, you may find you don't have the clearance under the ply to get it fitted.
When I did this one:
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