Silicone Sealing

Silicone belongs at junctions, where two surfaces meet and move slightly. Rigid grout would crack there; flexible silicone stays watertight. We reseal:

• Baths: The joint between the bath and the tiles or wall panels.
• Showers: Around shower trays and along enclosure and screen profiles.
• Basins and vanity units: Where the basin or worktop meets the wall.
• Kitchen worktops and sinks: Along upstands and splashbacks, and around inset and undermount sinks.
• Window frames, inside: Around the inside of window frames and window boards in kitchens and bathrooms, where condensation runs down.

1. 1

   Remove the old silicone: every trace is cut out, because new silicone does not bond to old.

2. 2

   Clean and treat: soap residue is removed and any mould treated.

3. 3

   Dry the joint: silicone will not stick to a damp surface.

4. 4

   Fill the bath: a full bath drops slightly, so we seal it full and the sealant is not stretched each time it is used.

5. 5

   Apply and tool: sanitary silicone with a fungicide goes on in one continuous bead and is smoothed to a neat profile.

6. 6

   Leave it to cure: typically around a day, depending on the product, before the bath or shower is used.

If the bath itself moves when you stand in it, the sealant will keep splitting. The bath needs firmer support from our bathroom plumbing team first.

Old silicone is cut along both edges with a blade or plastic scraper and pulled out in strips. The film left behind comes off with a silicone remover and a non-scratch pad. Acrylic baths and trays scratch easily, so we avoid metal scrapers on them. Sealing over old silicone is the most common reason a new seal peels off.

Mould needs moisture, warmth and something to feed on, and bathrooms supply steam, warmth and soap residue. Once mould grows into the silicone, the marks are inside the sealant, so cleaning only lightens them. The fix is to remove it and reseal. To keep new silicone clean for longer:

• Ventilate: Run an extractor fan or open a window. A new fan can be fitted through our domestic electrical installation service.
• Dry the joint: Wipe or squeegee the sealant after showering.
• Use the right product: A sanitary silicone with a fungicide slows mould growth, though no sealant is completely mould-proof.

There is no fixed interval; it depends on use, ventilation and how well the seal was done. Reseal when you see:

• black or pink mould that will not clean off
• gaps, splits or sealant pulling away from the wall or the bath
• water staining on the ceiling below, or a damp smell behind the bath panel
• loose or hollow-sounding tiles near the bath

Staining or loose tiles may mean water has already got behind the seal. Our leak detection and pipe repairs service can find the source.

Silicone seals the line between the worktop and the wall or upstand, and the edge of the sink. On natural stone and quartz we use a neutral-cure silicone, because some standard silicones can mark stone. Timber worktops need their cut edges oiled first. If water is coming from the sink waste or tap rather than the seal, it is a job for our kitchen plumbing service.

Around windows and skirting boards that will be painted, the gaps are filled with decorator's caulk instead, because silicone cannot be painted.

Each does a different job:

• Silicone: A flexible seal for junctions between different surfaces, such as a bath and tiles.
• Grout sealer: Brushed into grout lines to stop water and stains soaking in. See sealing tile joints for waterproofing.
• Regrouting: Replacing cracked or stained grout. See re-grouting tiled surfaces.
• Tanking: A waterproof layer behind tiles in wet areas. See installing kitchen and bathroom tiles.