ᐅ Mold under the shower tray?

I removed the old silicone sealant between the tiles and a

shower tray. The sealant was leaking. There are remnants of the underlying material on the old silicone, as the tiles do not fully cover the edge of the shower tray. These remnants are also slightly blackened, which could be mold.

What can I do to make sure any mold present in this hard-to-reach area is removed? I cannot remove the shower tray.

Thank you

I would spray an anti-mold agent into the gap, let it dry, and then seal everything with silicone.

Niloa schrieb:
I would spray an anti-mold agent into the gap, let it dry, and then seal everything with silicone.

Oh no, definitely not. If the mold is not completely removed, it will grow back quickly.

Gerd53 schrieb:
What can I do to make sure to remove any mold that might be present in this hard-to-reach spot? I can’t remove the shower tray.

If it is properly installed, there should be a sealing tape between the shower tray and the wall plaster, and the wall should be waterproofed with a liquid membrane (the blue material on the wall). The tiles are not installed behind the shower tray; instead, the tray is installed first (with sealing tape), then the tiling is done, with the tiles ending just above the shower tray. The gap is then filled with backer rod and sealed with silicone. The backer rod saves silicone and also prevents the silicone from adhering to the shower tray, tiles, AND the wall simultaneously (three-sided adhesion), which would greatly reduce elasticity and cause the silicone to crack quickly.

In your case, it seems the tray was installed and tiled, and then silicone was pressed in without backer rod. This is a common practice. It’s possible but not ideal.

If you want a long-term solution: remove the tray, take off at least the bottom row of tiles, reinstall the tray with sealing tape and liquid membrane, retile, and then finish with silicone and backer rod.

A short-term patch: push a permanently elastic sealant into the gap from behind, wait, insert backer rod and silicone, and repeat every five years.

I heard from an acquaintance who spent many years in Brazil that to prevent mold, for example in closets without windows, a light bulb was left on. This generated some heat and air circulation.
My suggestion:
Use mold spray and remove mold where accessible. Then seal the bathtub or area where water can get in. Leave openings in other places to allow warmth and air circulation or ventilation. This should help control the problem with minimal effort.