Kitchen sealant does a quiet job. It stops water running down the back of the worktop, into the sink cut-out or behind the upstand. When it shrinks or splits, water gets into chipboard and timber, and the first sign is often a swollen edge or a musty cupboard. This guide covers where sealant goes in a kitchen, why it fails and how to keep it sound.
Where kitchen sealant goes
- Worktop to wall or upstand. The long joint along the back of the worktop, where splashes run down.
- Upstand or splashback to worktop. The joint along the bottom of a tiled, glass or laminate splashback.
- Around the sink. Inset sinks usually sit on a seal or gasket. Undermount sinks rely on sealant between the sink rim and the worktop.
- Worktop joints and end caps. Where two lengths of worktop meet, and at exposed ends.
Hobs usually come with their own seal from the manufacturer. Follow the fitting instructions rather than adding a bead of silicone, which can make the hob hard to remove later.
Why water gets behind worktops
Most worktops have a core of chipboard or timber. Once water reaches the core, it swells, and swelling can’t be reversed. Common routes in are:
- Sealant that has shrunk away from the wall over the years
- A bead laid on a dusty or greasy surface, which never bonded properly
- Cracks where the worktop flexes, such as near a dishwasher or corner joint
- Cut edges around the sink that were never sealed
A real example
At a kitchen in Harper Drive, Maidenbower, the sealant was around 30 years old. It had shrunk, and water had been getting behind the worktop. We removed it all and resealed with a colour-matched sanitary silicone, using a food-safe product beside the sink. The work was done the same day.
Jobs like this are part of our resealing service, which covers kitchens as well as bathrooms.
Need it done properly? Mr Mastic covers the South East, London and Scotland, with a one-year guarantee on every job. Call or email for a quick quote.
Choosing the right sealant
Kitchens need a flexible sealant that copes with water and cleaning. Anti-fungal sanitary silicone is the usual choice along worktops and upstands. Beside the sink, where food may touch the surface, choose a product the manufacturer states is suitable for food areas.
Colour matters more in a kitchen than a bathroom, because the joints are at eye level. White, clear and a range of greys, browns and blacks are available. Our guide to colour matching sealant covers the options. Decorators’ caulk is not suitable for these joints. See caulk vs silicone.
Keeping kitchen joints sound
- Wipe up standing water along the back of the worktop rather than leaving it to sit.
- Clean the bead with a mild cleaner and a soft cloth. Avoid abrasive pads and strong solvents.
- Look along the joints when you clean. A dark line, a gap or a lifted edge is the time to act.
- Check inside the sink cupboard now and then for damp or swelling.
Undermount sinks and stone worktops
Undermount sinks hang below the worktop, so the joint between the sink rim and the underside of the worktop is hidden and gets wet every day. If that sealant fails, water drips into the cupboard below or soaks into the worktop edge. A torch inside the cupboard is the easiest way to check it.
Stone and quartz worktops don’t swell like chipboard, but water behind them can still reach the wall, the units and the floor. Some natural stone can also be stained by the wrong sealant, so use a product the manufacturer lists as suitable for it.
Quick answers
Can a swollen worktop be fixed with sealant?
No. Sealant can stop more water getting in, but once chipboard has swollen it doesn’t go back. Badly swollen sections may need replacing.
Should I seal the gap between the hob and worktop?
Usually not. Hobs come with their own seal. Check the manufacturer’s fitting instructions first.
How long before I can use the sink?
Keep water off new sealant for the cure time given, usually around 24 hours.
Related services
More advice
- Coloured Sealant and Colour Matching
- Decorator’s Caulk vs Silicone: Which and Where
- How to Remove Old Silicone Sealant
- All advice
This guide is general information about sealant work. It isn’t legal, fire-safety or structural advice; for those, speak to a qualified professional.