John Rumm wrote in
o.uk:

On 13/05/2019 17:44, DerbyBorn wrote:

If the wood is properly seasoned prior to installation, then it
ought not shrink any further. I would use pressure treated 4x2 for
the basic framework, with a top layer of 19mm WPB ply, and then if
its a stone resin tray, bed that onto a half inch screed of sand and
cement - probably with a bit of SBR in there as an admixture.

When installing the tray, butter the wall facing sides with
silicone, and rule off the bead cleanly at the top edge of the tray.
Then tiling / boarding - bring those down toward the tray, but leave
a 1/4" gap, to later fill with silicone. Having a wide enough bead
ensures it will get good adhesion, and also will tolerate any small
amount of movement.



Sounds good - thanks


I was thinking of getting a 1700mm tray and that would need chopping
into the wall as is the bath it is replacing, The space is about
1680mm. I am now thinking this is additional work for no real benefit
and am now thinking of a 1600mm tray. This will leave a small gap to
be dealt with.

Chopping a bath into the wall can be worthwhile - its a way of making
a lighter weight acrylic bath far more rigid. For a shower tray there
is no real advantage unless you need to do it to squeeze in a
slightly oversized tray.

Do you think it is a better way? Any thoughts on the "gap"

It sounds like you will end up with 80mm of gap. The tiles (depending
on type) could take up say 30mm, which leaves at least a couple of
inches. So perhaps some 1" deep battens on the end walls, and a sheet
of aquapanel or hardibacker fixed to them to bring the walls out to
the right spacing?

(that might amount to more work that chopping the tray in 10m on each
end!)


Long term leakage risks?

Handling a heavy tray into the chopped out walls - difficulty in
replacing it if ever needed?