Shower Tray Problem

18 Oct 2006
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United Kingdom
Just installed a new shower tray, stone resin tray (1700x800) bedded on mortar and everything solid while tiling completed and siliconed in.
First time it was used wife reports that the centre of the tray has some give…….

Anyone any suggestions as to the issue? Tray was rigid before installation so surprised that it is giving without a line showing where the resin is cracked.
Any solutions other than tear off the bottom row of tiles and replace the tray?
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Take the tray out, remove the mortar, ply the area where the tray is going and use rapidset to stick the tray to the ply
All instructions with trays ask for it to be bedded on mortar. But find that it shrinks and the tray is just left floating and not fixed.
agree with the above reply, drywall adhesive or rapid does a better job
The more I look at it the more I think the plastic has separated from the resin but it may be my imagination. The movement didn’t appear until the shower was used and about a month after the tray was installed.

Installed a slightly smaller one (1400x800) the same way last year and it is fine.

Have been trying to avoid the inevitable but will have to bite the bullet and take some tiles off to get the tray out☹️☹️

wary of products which say “rapid” as I don’t work that quickly, will probably try drywall
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Drywall adhesive and rapid set have roughly
the same drying times, I personally wouldn’t use drywall adhesive, I’d use flexible rapid set, I’ve installed well over 200 trays with rapid set and had no problems
The floor is 22 mm sealed chipboard. Expecting eye rolls. I feel that replacing this with ply will weaken the floor - joints to ply will not be as strong as joists may not be where the joints are.

Do you put ply on top or replace the chipboard?
Replacement tray arrived FoC, just need to strip the old one out, the more we stand on it the more it seems to move, and the more it seems to be the skin only. Just need her indoors to allow me to make a mess, again! The shower is usable, it just feels awful and rustly under your feet.
If the chipboard is still fine will screw some WPB ply down and then rapid set. Final decision when I get the tray out and check the chipboard.
Striped the bottom row of tiles out with a diamond blade (I wish she hadn’t picked porcelain tiles) and removed the tray. Problem may have been water getting into the chipboard floor (my fault for not getting the waterproofing right).

The bottom of the tray that came out is noticeably concave which may have been the problem, the replacement is flat.

Spent some time stiffening the floor (3*2 screwed to the floor between the joists with 60mm long 5mm screws and the floor screwed to the joists (20 year old house with 21mm waxed chipboard glued to the joists). Fixed guides either end so I could ensure that the screed was level, installed new tray and left it for a couple of weeks to check there was no movement before I retiled.

Been back in use for 6 weeks and all is fine.

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