"Andy Hall" wrote in message
...
On Wed, 18 Aug 2004 13:29:22 +0000 (UTC), "Charles Middleton"
wrote:

This could be a bad idea. The waste plumbing for a shower tray is
either 32 or 40mm so I would check. Also you have to have a
reasonable slope for the water to run away. Drilling holes of this
size in a floor joist can be a bad idea because of the weakening
effect - I would seek professional advice on that.

Another badly planned project on my part then. I'm not sure what other
options I have and the shower & tray is arriving tomorrow. I thought that it
was safe to put holes in the joists providing that a) it was close to the
supporting wall and b) the hole went through the middle of the joist and c)
the diameter of the hole was no bigger than two thirds of the joist?

Also, I was planning to put a slight incline on the run through the joists
to provide this.

Generally 18mm WBP ply (commonly available) is a good choice.

So board the floor with 18mm WBP and then mount tray on motor base on top of
that.

You need a mortar base for the whole thing. This is to take out
unevennesses in the finish of the underside so that the load is spread
evenly. The manufacturer's instructions will normally stipulate it
and void the warranty if you don't.

So the mortar really provides a base between the ply and the bottom of the
tray which I presume doesn't touch the floor. Its likely in this case then
that the mortar will be contained inside and underneath the tray - no
problem.

CM.