How to tell if your shower silicone has failed

The silicone lines in a shower sit where two surfaces meet, such as wall to floor, wall to wall, or tile to bath. Those are the places where tiled surfaces move slightly and where grout is the wrong material, because grout cracks when a joint flexes. Silicone is there to take that movement and keep water out.

It does not last forever, and it often fails slowly enough that you do not notice until water has been getting through for a while.

Visible signs of failure

• Black or dark green spots that are inside the silicone, not just sitting on top
• Edges that are lifting or peeling away from the tile or the tray
• Gaps or splits, even thin ones, along the length of a bead
• Silicone that has shrunk, leaving a visible slot between it and the tile
• A yellow or brown tint, or a surface that looks chalky
• Silicone that feels hard and brittle rather than slightly rubbery

Mould: surface or through the bead?

This is the single most useful check. Surface mould sits on the outside and can usually be wiped off with a bathroom cleaner, leaving clean silicone behind. If dark staining stays after cleaning, or the dark colour runs deep into the bead and along its underside, the mould has grown into the material and it will keep returning. Cleaning will not fix that.

Try the finger test

Press gently along the bead with a dry fingertip. Healthy silicone is firm but slightly springy and stays attached along the entire length. If you feel a section that lifts, peels like a strip, or has a gap behind it, adhesion has failed even if it looks fine from a metre away.

Check the bottom corners of the shower especially. Water collects there and those joints work the hardest.

Signs the problem has moved past the silicone

Failed silicone is a nuisance. Water that has been getting behind it for months can cause bigger problems. Look for:

• Grout near the joint that is permanently dark or soft
• Tiles that sound hollow or have started to move
• Swollen or bubbling paint, or a musty smell in the adjoining room or cupboard
• Damp patches or staining on the other side of the shower wall

If you see any of these, replacing the silicone is the minimum rather than the whole answer. Something behind the tiles may need looking at.

How long silicone typically lasts

There is no single number, because it depends on the product used, how well the joint was prepared, how much the shower is used and how well the room is ventilated. A well-installed bead in a well-ventilated bathroom lasts much longer than one in a closed room that stays damp. Rather than going by age, go by condition.

What you can do about it yourself

Replacing a short run of silicone is a manageable DIY task. You remove the old bead with a silicone-removal tool or a sharp blade, clean the joint with a solvent so no residue remains, let it dry completely, tape either side, apply a bathroom-rated silicone and smooth it with a tool before removing the tape.

The common mistakes are leaving behind a film of old silicone, applying new material to damp joints, and using a general-purpose product with no mould-resistant additive. Any of these shortens the life of the repair, often to a matter of months.

When to call someone

Full-shower resilicones, joints that have been leaking, or any bathroom where you suspect water has gotten behind tiles are worth putting in a professional's hands. A tradesperson can also check the surrounding grout and tiles at the same visit, which is useful when you are not sure how far the problem extends.