That thin line of rubbery filler around your sink, bath and kitchen worktop does a bigger job than it looks. Silicone sealant keeps water out of the gaps where two surfaces meet, and when it fails you get seeping water, black mould and, eventually, damage behind the tiles. The good news is that renewing a tired bead is one of the most satisfying and beginner-friendly repairs in the home. In our warm, humid flats, sealant discolours and lifts faster than in cooler climates, so knowing how to replace it is a genuinely useful skill. This guide covers choosing the right product, removing the old sealant, and running a clean new bead you will be proud of.
What Silicone Sealant Does and Where You Need It
Sealant, sometimes called caulk, is a flexible filler that bridges the gap between two surfaces and stops water passing through. Unlike grout, which is hard and sits between tiles, silicone stays slightly rubbery so it can flex as surfaces expand, move or settle without cracking. That flexibility is exactly why you find it in the spots that get wet and move a little.
Common places it earns its keep in an HDB flat include:
- Around the kitchen sink and where the worktop meets the wall.
- The join between a bath or shower tray and the wall.
- Around the base of taps and the edge of a vanity basin.
- Gaps around window frames and skirting where you want to block draughts or water.
If a bead has gone black, is peeling away, or lets water seep behind it, it is past saving and needs replacing rather than patching over.
Choosing the Right Sealant
Not all tubes are the same, and buying the wrong one is a common first mistake. For any wet area, you want a sanitary or “mould-resistant” silicone, which contains additives that resist the black mould our bathrooms attract. Reach for a general silicone for windows and dry gaps, and use a paintable acrylic type only where you plan to paint over it, since true silicone will not take paint.
| Type | Best for | Waterproof? | Paintable? |
|---|---|---|---|
| Sanitary silicone | Kitchens, bathrooms, wet areas | Yes | No |
| General silicone | Windows, general gaps | Yes | No |
| Acrylic caulk | Skirting, gaps to be painted | Water-resistant only | Yes |
Buy a colour that suits the job, usually white, clear or grey, and check whether you need a caulk gun. Most sealant comes in cartridges that fit a simple, inexpensive gun; smaller squeeze tubes exist for tiny jobs but are harder to control.
Tools and Materials You Will Need
You do not need much, and most of it is cheap at any local hardware shop or DIY store.
- A cartridge of the right silicone and a caulk gun to fit it.
- A sharp utility knife or a plastic sealant remover tool.
- An old cloth, kitchen roll and a mild cleaner or rubbing alcohol.
- Masking tape for crisp edges, and a smoothing tool or just a clean finger.
- Gloves, and open windows or a fan for ventilation.
Work in a well-ventilated space, as uncured silicone gives off a strong smell until it sets. Open the window and run the exhaust fan while you work and for a while afterwards.
Removing the Old Sealant Cleanly
A new bead is only as good as the surface under it, so take your time stripping the old one out completely. Skipping this step is why so many DIY repairs peel away within weeks.
- Soften and slice: run a sharp blade along the top and bottom edges of the old bead, then peel the strip away in one piece where you can.
- Pick out the remnants with a plastic scraper, taking care not to scratch the tiles, enamel or worktop.
- Clean the gap thoroughly. Wipe away any residue, then go over it with rubbing alcohol to remove soap film and grease. New silicone will not bond to a dirty or greasy surface.
- Dry it completely. Any trapped moisture will stop the sealant curing and can seal mould in behind the new bead. Give it plenty of time, especially in humid weather.
If the old sealant hides active mould on the wall or tile, treat and dry the area first rather than sealing the problem in.
How to Apply a Neat Bead
This is the part that looks intimidating and is actually easy once you commit to a steady, continuous motion. Practise a short run on some cardboard first if it is your first time.
- Cut the cartridge nozzle at a 45-degree angle, making the opening roughly the width of the gap. Load it into the gun.
- For crisp lines, run masking tape along both sides of the gap, leaving a channel the width you want the bead to be.
- Hold the gun at 45 degrees, squeeze the trigger, and draw it steadily along the gap in one smooth pass, pushing a little sealant ahead of the nozzle.
- Smooth the bead immediately with a wetted finger or a smoothing tool, in one continuous stroke, to press it in and leave a slight concave finish.
- Peel the masking tape away straight away, while the silicone is still wet, pulling at a low angle.
- Wipe your tools and any smears before they set.
Consistency beats perfection. A slightly wavy bead that is well bonded will outlast a neat one applied over a dirty surface.
Curing, Aftercare and When to Call a Pro
Freshly applied silicone needs time to cure before it gets wet. Most types need a full day, so keep the shower dry and avoid running water over a new bath or sink bead until it has properly set; check the tube for the exact time. Once cured, a quick wipe now and then and good ventilation after showers will slow the return of mould.
Silicone sealant is firmly in DIY territory, but know the line. If you find rot, crumbling tiles or water damage behind a failed bead, the problem is bigger than the seal, and major waterproofing or wet-works in bathrooms should be handled by a professional. Concealed pipes, water heaters and anything behind a wall need a licensed plumber. And if a leak persists after you reseal, stop guessing and call a pro before hidden damage spreads. For a small kitchen or bathroom bead, though, an afternoon and a steady hand are all it takes to keep the water where it belongs.