another leaky shower question

Hi folks,
Here's a wet-floor type shower question, sealing of.
Because I could, and with some help from the folks here I built a wet area type shower 'cos both of us were fed up with cramped shower cubicles.
The area is about 5'x5' and consists of a 1200x1200 shower tray with the surrounding area built up of flooring grade MDF (fastened to old wall beams I had lying around which are screwed to the floor) with Aquapanel screwed to that and floor tiles on top of that.
All fine and dandy, but there's still a tiny gap between the edge of the shower tray and the surround. Originally I had this filled with Unibond power shower sealant, but for some reason I haven't fathomed yet (mentioned in another thread) once in use the shower tray managed to drop 2 or 3 mm.
I say I haven't fathomed this yet because the tray is simply sitting on the level-ish floorboards - I don't believe any of the 3 layers of the surround could've expanded that much to cause the effect we got.
Basically the tray moved and the unibond sealant was so strong it broke the grout between the tiles and the tray resulting in Much Leakage!
Here's a pic of the floor before all this happened:
http://vorbis.demon.co.uk/shower-floor.JPG
Note white sealant all over the place.
The tiles themselves are the pebble mosaic effect types available from bigger B&Qs and other places:
http://www.diy.com/bq/product/product.jhtml?PRODID $646&CATID7233
and its the grout between these that appears to be breaking down - cracks are visible between some of the panels and running along the edge where grout meets glass brick walls.
So! I need to re-seal the tray and heal the cracks in the grout, but the design of the tiles might inhibit this somewhat.
Anybody still with me or have you all moved to a shorter message? :o))
All hints and tips appreciated - being able to shower in a space that big is great, particularly the amount of water the shower itself can chuck out, and we're all missing it!
cheers
witchy/binarydinosaurs
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You haven't noticed any water marks on the ceiling below ?
Have the joists below moved down because they are now wet or can't take the extra weight ?
If you've checked that the main structure is sound, then it is probably just a case of expansion and contraction. You will have to persevere with the filling in and re-grouting again.
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On Wed, 08 Oct 2003 19:41:18 GMT, "BigWallop"

Thanks for not quoting my message :) It was bloody long!
It was water marks on the ceiling below that raised the alarm. I knew once I saw the change in the sealant and the cracks in the tiles that there'd be trouble; fortunately it didn't fuse the downstairs lights whilst dripping onto a downlighter in the kitchen :)
I reckon I'm OK with the weight because where the shower is used to be the old victorian bathroom. I've tried to draw it as it was in ascii but it looks kak. Basically where the shower is now used to house the original bathroom, a lath/plaster wall and a BFO lead lined water tank that had to be broken up in situ because it was too heavy to shift.
The glass brick walls that contain the shower are built on wood that's been screwed to the joists of the floor below and the wall beams, and the shower tray itself if resting on 2 joists that haven't moved otherwise I'd have problems in the adjacent toilet as well as the kitchen ceiling :o)
I think yer right with the expansion; it's the first shower I've ever built and I could bore people here rigid with pictures of the progress over the last 3 years.......the telly programme people would have a field day if they saw what we've had to do, but once they'd seen it we'd have to kill them :)
cheers
witchy/binarydinosaurs
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wrote:

the
just
LOL !!!
If the shower tray is only resting directly on two joists without boards, then it might not be spreading enough weight to hold the tray with a body in it. I personally would have set the tray on some flooring grade board on top of at least three joists. This would help spread the weight and also stop the joists from rocking sideways when you move around in the shower tray.
You may not notice any movement when you're in the shower, but the joists only need to rock a couple of millimeters at a time to loosen them off their anchors. Then over time the joists will be moving around enough to make the tray wobble.
The tray itself will also be flexing under your weight as you move around, which will also contribute to the sideways movement of the joists. The tray may feel rigid enough to take anything you throw at it, but if it is just resting directly on the joists without any additional support underneath, then its base will flex.
If it's possible to have a look from below while you're repairing your wet ceiling, then take a look at the joists when someone is moving around in the tray as if taking shower.
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On Thu, 09 Oct 2003 00:49:36 GMT, "BigWallop"

Oop, my bad :) The tray is a stone resin job and it's just sitting on the floor - floorboards and all. The only extra thing I did was lift a board next to it so I could get at the shower trap and fit the plumbing; the trap itself goes through a hole in a board.
Here's a 'before' pic:
http://vorbis.demon.co.uk/dscf0231.jpg
The only thing I wish I'd done is stick a bed of mortar down before I added the surrounding woodwork.....
cheers
witchy/binarydinosaurs
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wrote:

in
Ah Ha ! That's OK then. When you said it was sitting right down on the joists, I did panic a bit. :-)) But it is on the floor boards. Phew ! Then it is down to being normal expansion and contraction then, and will probably be cured with a new fill of the cracking. Just things settling in. :-))
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On Thu, 09 Oct 2003 13:16:57 GMT, "BigWallop"

I 'ope so - we're all missing the shower!
cheers
witchy/binarydinosaurs
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