Advice needed on tanking wall-to-ceiling and wall-to-shower tray joints

[Waluigi]

Hmm, I’ve got a dilemma then. I’ve alresdy siliconed between the tray and the bottom of the wall. Do you suggest I remove this Silicon and replace with something else than I *can* tank (caulk??), or should I just apply the tanking to the wall only for now and rely on the Silicon underneath as a water barrier (note that this will be behind tiles and a further line of sealant between bottom of tiles and the tray).

You’ve got Hardiebacker on the walls right?

I’d lay a blade flat onto your tray and score through the Silicon, then scrape the Silicon off the wall with a scraper. Leave the Silicon that’s between the tray and the wall. Then tank, then a bead of sealant on top. Hopefully that makes sense.

 

[widler]

You’ve got Hardiebacker on the walls right?

I’d lay a blade flat onto your tray and score through the Silicon, then scrape the Silicon off the wall with a scraper. Leave the Silicon that’s between the tray and the wall. Then tank, then a bead of sealant on top. Hopefully that makes sense.

Why just take a mm or two of Silicon off the wall , than tank, the Silicon is doing the same as the tanking would

 

[Waluigi]

Yes and no.

For me personally I think it’s a better job to apply Silicon to tanking rather than trying to tank next to or on top of Silicon. For the reasons stated above.

 

[One Day]

I've seen too many cases where Silicon (usually clear) degrades and debonds over time.
Far better to carefully bond a tape to the tray using something like Kerdi-fix / Wedi 610 (a good elastomeric adhesive) and then the tape into the tanking.
Personally, I think Silicon should be seen as a cosmetic rather than a functional product in wet areas.

 

[Boggs]

I always seal round with either Sticks Like S**t or CT1, that way you can tank over it as it’s paintable.
Mask off round the tray about 5mm in, apply tanking and remove the tape.
Use 2mm spacers between tiles and tray and fill the gap with Silicon when finished.

 

[Qwerty]

I use Marmox sealant or Ceresit FT101 on the wall tray join and then paint over with paint on membrane