Troublesome silicone install

[John Rumm]

Got an interesting problem with a mate's shower tray where the silicone seal keeps failing.

All proper methods of prep and application have been used (Mechanical removal, clean down with IPA, apply with Fugenboy etc) but the seal fails within a few months. Looking at replacing it for the third time now...

The failure mechanism seems related to the tiles; which are a large

300mm square 15mm thick travertine marble ones with a matt finish. The seal always seems to part from the vertical surface against the tiles while remaining stuck like shit to a blanket on the (stone resin) tray itself.

We have tried several brands of silicone - the posh dow corning one lasting less well than the basic screwfix sanitary.

[Lobster]

Do the faces of the matt tiles need sealing with something-or-other at the edges, where the silicone is to be applied? Could they be porous and are exuding some form of grease/soap?

David

[John Rumm]

I expect this is probably the case... I did suggest that he try some Lithofin stainstop on them first, but I doubt that will happen.

Perhaps I ought to mask of the section where the bead will go and spray it with something before next applying the silicone.

[Pete Cross]

Stand in the tray as if having a shower and see if the gap under the tiles increases by a large amount. We had similar probs with our bath due to springy old floorboards underneath.

Pete

[Pete C]

How about painting a little superglue on to see how well it sticks to the tiles?

cheers, Pete.

[Lobster]

AFAICR that doesn't fare well with water, does it? David

[John Rumm]

No, its rock solid...

(good suggestion though! ;-)

[Pete C]

AFAICT it's waterproof:

cheers, Pete.

[Andy Hall]

Yes it will behave like this.

The tiles should have been treated with two coats of Lithofin MN Stainstop before silicone goes near it.

I tried the experiment recently both ways with some limestone. No sealer and the silicone doesn't adhere properly. Use Stainstop and it does.