Silicone Joints And When They Need Replacing

Silicone is the only part of a bathroom that is designed to be replaced, and it is the part nobody replaces until it has already failed.

A bead in a wet shower has a few years in it. After that it is a path for water rather than a barrier.

What the silicone is actually for

Not waterproofing. The membrane under the tiles does that, and it is the subject of [waterproofing you never see](/blog/waterproofing-you-never-see-the-membrane-under-every-wet-area).

Silicone seals the movement joints, meaning the places where two different surfaces meet and move independently: wall to floor, wall to wall in a corner, around a bath, at a shower screen, and around a tap or waste penetration.

Those joints move. Grout is rigid and cracks when they do, which is why they are filled with a flexible sealant rather than grout in the first place.

Which means a corner that has been grouted instead of siliconed is a fault, not a finish choice, and it will crack on schedule.

How it fails

It shrinks and pulls away from one side, leaving a hairline gap along the edge. The common failure and the hardest to see, because the bead still looks continuous.

It goes black. Mould growing in and under the bead. Once it is in the silicone it cannot be cleaned out, because the growth is below the surface.

It goes hard and splits. Silicone loses flexibility with age and UV, and then it cracks the first time the joint moves.

It peels off in a strip, which means it was applied over a dirty or wet surface and never bonded.

The gap is the one that matters. Water goes through a hairline gap readily, and the place it goes is behind the tiles, where it sits against the substrate and nobody sees it for a year.

Why recaulking over the top does nothing

New silicone does not bond to old silicone.

Which means a fresh bead run over a failed one is sitting on a surface that is already letting water past, and the water path underneath is unchanged. It looks better and performs identically.

The old bead comes out completely. All of it, including the thin film left in the corner, because that film is what the new bead would be bonding to.

Doing it properly

The removal is most of the work and the part that decides whether the new bead lasts three years or ten.

Cut the bead out mechanically rather than trying to pull it, and get the residue off the tile face and out of the corner.

Kill what is in the joint. If there was mould, the joint is treated, not just wiped, or the new bead goes black from underneath.

Get it dry. Silicone applied into a damp joint will not bond. In a shower that is in daily use that means the shower stays out of service for long enough to dry properly, which is usually longer than people expect.

Use the right product. A neutral cure sealant where it is in contact with stone, because an acetic cure silicone stains marble and some engineered stone. A sanitary grade with a fungicide in a wet area. Anything general purpose from a hardware shelf is the wrong product for a shower.

Tool it properly, so the bead is concave and thin at the edges rather than a thick rounded ridge. A heavy bead traps water against the tile and it is the first thing to peel.

Let it cure before the shower goes back into use. Most sealants need a day, and a bead that gets wet while curing fails early.

When silicone is not the answer

Three cases where new silicone is a cosmetic fix on a real problem.

Water appearing below a shower, which is a membrane failure, not a joint. New silicone hides the symptom and the leak continues, which is why [the leaking shower keeps coming back](/blog/the-leaking-shower-why-it-keeps-coming-back).

Loose or drummy tiles around the joint, which means the bond under them has gone. Sealing the edge of a failing tile field does nothing, and the signs are set out in [tile and grout failure](/blog/tile-and-grout-failure-what-it-tells-you).

A shower screen that moves when the door opens. The silicone is being pulled, and no sealant survives a screen that is not fixed properly, which belongs with [shower screens and bathroom hardware](/blog/shower-screens-and-bathroom-hardware).

As a scheduled item

Across a portfolio this is the lowest cost preventive job on the list.

Silicone replaced on a cycle in every wet area, before it fails, costs very little per bathroom and it removes the water damage claims that start as a hairline gap in a corner. It belongs on the planned list rather than the reactive one, which is the whole argument in [emergency or scheduled](/blog/emergency-or-scheduled-what-warrants-a-callout).

Ample replaces silicone and repairs wet area joints across apartments and houses in the eastern suburbs and inner city, with the tiling, waterproofing and screen hardware handled by one team.