Shower silicone caulk keeps failing, options for never fail?

Question

So, I have two issues. Both related to the same solution. One shower keeps breaking the silicone seal and then letting water through. The other shower has standing water against the silicone and I'm worries that if this seal breaks it will leak severely.

The tray is up as close to the tiles (3mm) I can get in one case, but pretty gappy in the other tray 3mm-10mm gap.

So, I'm looking for what is the best way to double belt and brace this seal? is there some industrial strength stuff I can use, or could (should) I use expanding foam or grout in the gap before silicone?

Answer 1

You can fill the gap with sealant, then let it set (which might take longer than you think, even a day or two) before doing the actual seal.

For the one where the sealant is failing, there are two main causes - either it didn't stick very well in the first place or the two sides of the seal are moving apart (hence the advice to fill a bath before sealing round it). If there's movement you need to deal with the underlying cause.

If its not sticking very well, cleaning the surfaces with methylated spirit (denatured alcohol) may help.