Advice requested: seal bottom row of tiles to a bespoke shower base

Hi Folks, We have a shower cubicle of a non-standard size, with block walls on three sides. I got a custom shower tray made from stainless steel for the base of this shower, with a lip on it of about one inch. I tiled the walls of the shower and rested the bottom row of tiles on to the stainless steel base, so that shower water would fall into the base and drain away nicely: no worries about the integrity of the join twixt tiles and base here. I then bought the good silicone stuff (can't remember the brand name, but each cartridge was £7.50 a time all those years ago) and the shower has done well for a few years.
The problem started about a year ago: the other side of one of the shower cubicle walls is wallpapered, and the black bacterium started to flare in spots from the base up to about eighteen inches off the floor. The other wall is in an adjoining room, and it too showed the same symptoms. The tiles used are those flaming difficult ones to drill, and are about fourteen inches tall by about ten wide.
I cursed my luck and decided to remove the bottom row of tiles, and the plaster work behind them was damp. The plaster at the very foot of the tiles for up to about a half inch was sufficiently wet that you could "rub" it through your fingers. Bug*er.
Its dried out for about three weeks now, hence I'm getting pestered to get the shower fixed (we have two other showers in the house, so no catty comments about personal stench please :-) . But how to fix this: if I do what I did last time, the problem could come back. My guess is that the water was somehow "wick"ing up the back of the tile and up into the wall.
Current thoughts are to buy some of that plastic "quadrant" tile edging stuff (not the kind that is used to tile down to the top lip of a bath), and use this to keep the bottom edge of the tile off the stainless steel. I'd also make sure that the bottom two inches of the wall are painted with gloss paint so that any water on its surface wouldn't seep in and work its way through.
I'm using one of those two-pronged damp meter things; it's not exact science but its quite useful. The numbers have dropped since the shower was decommissioned, but I guess that's to be expected.
Grateful if anyone has views on this; many thanks in advance.
Mungo
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On 28/10/12 19:03, snipped-for-privacy@gmail.com wrote:

the way to fix this is to use silicioe to seal the tray to te plaster wall. and then tile up then re-tile with waterproof cement and grout.

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On 28/10/2012 19:03, snipped-for-privacy@gmail.com wrote:

The problem is that the tiles were sitting on the tray - so you couldn't get a decent bead of silicone *into* the joint. Before you put the tiles back, cut a few mm off the bottom edge, and prop them up until the cement has set. *Then* apply the silicone so that it goes right back to the wall.
Also make sure that you use good quality waterproof grout between the tiles.
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On 28/10/2012 20:33, Roger Mills wrote:

I would in the short term use some polythene and gafa tape and seal the damp area (maybe loose at the bottom as long as it overhangs the tray) that would allow using the shower until it dries out.
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On 29/10/2012 13:08, ss wrote:

I've used this stuff a couple of times & it works a treat http://www.homelux.co.uk/index.php?l=page_view&p=product_range
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On Monday, October 29, 2012 6:38:02 PM UTC, The Medway Handyman wrote:

Will investigate Dave - thanks for the reply.
Mungo
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On Monday, October 29, 2012 1:08:09 PM UTC, ss wrote:

Obliged for your kind reply, but I did mention in my original post that the house has two other showers that us residents can use in the meantime. Actually, it's a luxury to be able to take a bathroom offline whilst I contemplate and fix the problem.
Mungo
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On Sunday, October 28, 2012 8:33:56 PM UTC, Roger Mills wrote:

Great advice Roger: thanks. What sort of gap should I leave between the bottom of the tile and the stainless steel - my guess would be about three millimetres?
I was also pondering whether to gloss paint the bottom inch of the back of the tile (and its lower edge), as a precaution. Any thoughts there?
Regards
Mungo
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On Sunday, October 28, 2012 7:03:29 PM UTC, snipped-for-privacy@gmail.com wrote:

Could you use one of those 'tanking kits'. I had a similar set up to you and we tanked all the walls before tiling. The kits contain a fibre tape that you stick over the joint from wall to tray so that when you apply the tanking gunk you end up with a waterproof seal all the way from tray to ceiling! Robert
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Hi Folks, We have a shower cubicle of a non-standard size, with block walls on three sides. I got a custom shower tray made from stainless steel for the base of this shower, with a lip on it of about one inch. I tiled the walls of the shower and rested the bottom row of tiles on to the stainless steel base, so that shower water would fall into the base and drain away nicely: no worries about the integrity of the join twixt tiles and base here. I then bought the good silicone stuff (can't remember the brand name, but each cartridge was £7.50 a time all those years ago) and the shower has done well for a few years.
The problem started about a year ago: the other side of one of the shower cubicle walls is wallpapered, and the black bacterium started to flare in spots from the base up to about eighteen inches off the floor. The other wall is in an adjoining room, and it too showed the same symptoms. The tiles used are those flaming difficult ones to drill, and are about fourteen inches tall by about ten wide.
I cursed my luck and decided to remove the bottom row of tiles, and the plaster work behind them was damp. The plaster at the very foot of the tiles for up to about a half inch was sufficiently wet that you could "rub" it through your fingers. Bug*er.
Its dried out for about three weeks now, hence I'm getting pestered to get the shower fixed (we have two other showers in the house, so no catty comments about personal stench please :-) . But how to fix this: if I do what I did last time, the problem could come back. My guess is that the water was somehow "wick"ing up the back of the tile and up into the wall.
Current thoughts are to buy some of that plastic "quadrant" tile edging stuff (not the kind that is used to tile down to the top lip of a bath), and use this to keep the bottom edge of the tile off the stainless steel. I'd also make sure that the bottom two inches of the wall are painted with gloss paint so that any water on its surface wouldn't seep in and work its way through.
I'm using one of those two-pronged damp meter things; it's not exact science but its quite useful. The numbers have dropped since the shower was decommissioned, but I guess that's to be expected.
Grateful if anyone has views on this; many thanks in advance.
Mungo
I have just been dealing with a related problem with one of my showers.
It's a Matki tray with a built-in "tiling upstand" round the back edge. It's been in for about 10 years without any trouble except hairline cracks have appeared across all of the bottom row of tiles.
When I installed it I followed the instructions to the letter. The built-in "tiling upstand" is recessed into the wall, i.e. tucked in under the bottom edge of the Aquapanel walls. All tiles except the bottom row are fixed using tile adhesive in the normal way.
For the bottom row I followed the instructions carefully. The tray itself has a load of silicone sealant behind the edge, between the tray and the wall. This oozes over the top of the tiling upstand all round. So far, so good. For the bottom row of tiles, I put a big bead of ilicone over the front edge of the tiling upstand, and tile adhesive down to nearly the bottom of the aquapanel. The tiles were then squidged into this so they are mostly adhesive fixed, but their bottom inch or so is stuck (and sealed) with silicone. Then in one swift action I finished them off with a bead of silicone between the tiles and shower tray and neatly finished this. When all dry they were grouted in the normal way.
This was fine for about 8 years but then horizontal cracks appeared across all the bottom row of tiles. I assumed (correctly as it turned out) that with all the silicone behind, there was no real chance of water creeping through and soaking everything behind, but last weekend I finally plucked up courage to find my old stock of spare tiles and have a go at replacing the bottom row.
Getting them off was a right old faff. I used the angle grinder to cut a few slots so that I could break out sections without damaging the next row up. It turned out that the horizontal cracks were all in the area between the silicone and tiling adhesive - I guess the two materials move slightly differently so the tiles are stressed just there.
So now I need to work out the best way of re-sticking and re-sealing the new bottom row of tiles. Maybe there is a better (less flexible?) type of silicone for sticking and sealing the tiles to the tray?
For your stainless steel tray this method (bottom inch or so stuck using silicone) should give a good seal but it does seem to require some special trick (or extra strong tiles) to avoid cracking later.
Good luck!
Regards, Simon.
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Maybe silicone for the whole row, not just attaching them to the tray but also the wal above? But if the tiles are moving very slightly there's always going to be a problem where they butt up against the next row up that's more rigidly glued to the wall, and/or the grouted joint.
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