I posted a week ago feeling very daunted by the instructions for
fitting a stone shower tray and questioning the need for bedding it
into mortar. Thanks to all for the very helpful replies.

I have now built my frame and cut the 18 mm ply to shape. What
concerns me now is how thick does the mortar needs to be? My problem
is that there is very little space between the top of the compression
fitting on the shower waste, and the bottom of the ply. I guess I can
chisel out some of the ply to give greater clearance, but it would be
helpful for me to have an idea of how thick the mortar should be. I
guess not very thick as I did find flexible floor tile adhesive
recommended as an alternative. Any thoughts?

Keith

In article 67b487fe-ff0e-4196-82d8-
, says...
I have now built my frame and cut the 18 mm ply to shape. What
concerns me now is how thick does the mortar needs to be?


At its thinnest - non-existant. If the very lowest part of the tray is
just kissing the substrate through the bed of cement it won't matter -
what matters is that those bits of the tray that wouldn't otherwise be
fully supported are - by the mortar.

--
Skipweasel - never knowingly understood.

On Feb 15, 3:08*pm, John Rumm wrote:

That's probably why they normally suggest 1/2" ply ;-)

Having said that, I have done it on 19mm myself before. To make fitting
the waste easier, I routed out an area around the waste on the underside
- in effect reducing the board thickness to 12mm at that point. Then
bedded it on about 1/2" of mortar.

(I laid the bed, shoved a couple of scrap offsets of 15mm plastic pipe
over the mortar and pushed it in so that it was in contact with the
board. Dropped the shower tray onto the pipes (a couple of mm clear of
the screed) and lined it all up, then pulled out the pipes to drop it
into place)

--
Cheers,

John.

The recommendation for 18 mm ply came from this very newsgroup in
reply to my previous post! Certainly I feel happier with 18 mm as it
seems much more rigid than 12 mm 9 (although I suppose that doesn't
really matter once it's on the framework.

Thanks for the suggestion about the 15 mm pipe though. I was a bit
concerned about trying to lay a rather heavy shower tray on a bed of
mortar right up against two walls and having to jiggle it to make sure
it was properly bedded. Which brings me to another question - I get
the feeling it might be best to go for a fairly moist mortar mix - am
I right, and if so, how moist?

Keith