Walk-in shower: more standing water, tighter demands

Why it asks more than a tray

On a classic tray, water looks for the waste. In a walk-in, a film often sits on the floor and against the glass profile: standing water. That leans on adhesion and mould protection harder than a bead that sheds in five minutes.

A weak sanitary grade gives up earlier here. I use OTTOSEAL S100 on ceramic; for very heavy use, sometimes S140. On marble or granite, S70, so it does not stain.

A miss is not “a bit of mould”. It is water under the tiling.

Glass, fall and backer rod

The wall-to-floor meeting is the critical one. The floor falls towards the drain, so there is tension in the bead. If the fillet is skinny and there is no backer rod, it tears when the building moves.

You do not need to “butter the profile on both sides” with a fat sausage. Water that gets in under the profile by capillary action has to get out. If you close the whole perimeter, it rots inside. The screen also has to be mechanically solid before you seal. A vibrating panel is not a silicone problem.

Do not bed the glass straight onto the floor with no packing: the bead is crushed and fails early.

How I do it

1. Strip old silicone to the substrate, not over it.
2. Clean with a technical cleaner (soap and skin fat block the bond). Faces must be dry: moisture in the adhesive or screed, locked in, grows mould from the inside.
3. Closed-cell PE backer in deep corners: two-face adhesion.
4. Gun S100 or S140 under pressure, without air pockets.
5. Tool with a neutral finisher, not washing-up liquid.

The linear drain meeting (stainless against tile) gets sealed too. Pick chemistry that will bond to metal and ceramic.

Classic mistakes

Sealing while the joint is still damp. Shooting over cured silicone. Tooling with soap and then wondering why it goes black so soon: soap knocks out a lot of the protection.

Afterwards

Skin in a few hours is not a full cure. On a walk-in bead, 24 hours without a shower is the minimum; if the bead is thick, 48 is more honest.