Risky to me.

How confident can you be that this arrangement can be sealed tightly? Normally with a shower tray you have a wooden board beneath, and you can access the area beneath the tray if need be.

From your description it doesn't sound all that clever.

HM

[quote author=HM  link=1107889616/0#3 date=1108039790]How confident can you be that this arrangement can be sealed tightly? [/quote]

Oh I see. I guess I didn't explain very well.

Think of a conventional shower tray, enclosure and door. The tray normally ends up about 100mm off the floor on blocks. Now imagine lowering it until it's recessed into the floor. It wouldn't be any harder to seal. There main problem is access to the trap etc and that's probably no harder really than if you are building a wet room.

I finally found a photo but this one doesn't have a door.

http://www.bagno.it/slab_exp_1.JPG

I once did a similar thing for my wife's granny!  She was arthritic and a 4" step would have been impossible.  We built the granny flat (at my father-in-laws)with this in mind and shuttered the screed for the tray area leaving a recess of about 70mm below screed for the tray to sit in.

The trap and a length of waste pipe were assembled onto the tray and passed through the outside wall as the tray was lowered into position.  Tray bedded onto sand/cement.

The tray was a special 'flat' type with a minimal lip at the front edge for access but the tray had a high, thin upstand on the other three edges.  These upstands were let into the plaster so that the tiling came over them and weathered it all perfectly.

The end job was a flat shower tray flush with the floor of the bathroom (except for the minimal lip) and it looked good.  Of course with the trap and waste bedded into sand/cement it could not be allowed to leak, nor was there any way of getting at the underside but in my experience most trays cannot be 'got at' underneath once flooring etc is laid.

The trap had the removeable grating from above and the waste had an access cap immediately outside the wall.

All in all a good job!  

Thanks bstyle and jerryd.  I was reasonably sure it's possible but it's good to know it's been done before. I've seen them on the stands at building shows here in Belgium but salesmen always tell you it's easy. They do look very good - and better than the wet room approach in my view.

I found another photo of a shallow tray...

http://www.firedearth.com/SiteImages/Site_1/image/Shower%20Tray.jpg

...bit expensive though!