A step-by-step guide to removing old sealant and applying new silicone around a bath or shower: tools, preparation, application tips, curing time, preventing mould and fixing common problems.
Cracked or mouldy sealant around a bath or shower isn't just unsightly: it can let water seep behind and under the bath, causing damp, rot and damage to ceilings below. Resealing is a straightforward DIY job that takes a couple of hours plus curing time.
What you'll need?
- sanitary silicone sealant with a fungicide (in the colour you want);
- a sealant gun;
- a sealant remover tool or plastic scraper, and a craft knife (used carefully);
- silicone remover solution (optional);
- isopropyl alcohol or methylated spirits and lint-free cloths;
- masking tape;
- a sealant smoothing tool, or a wet finger with washing-up liquid solution.
Step 1: remove the old sealant
Cut along the top and bottom of the old bead with a knife or removal tool, then pull it away. Scrape off remaining residue. Silicone remover can soften stubborn bits. Take care not to scratch acrylic baths or tiles.
Step 2: clean and dry thoroughly
Clean the joint with isopropyl alcohol to remove soap residue and grease. If there's mould, treat it with a mould remover, rinse and let it dry. The joint must be completely dry before resealing; leave it overnight if you can. Silicone won't bond properly to damp or dirty surfaces.
Step 3: fill the bath
Fill the bath with water before sealing. This lowers it to its "loaded" position, so the sealant isn't stretched and cracked when you next use it. Leave the water in until the sealant has cured. (Not needed for shower trays.)
Step 4: mask the joint (optional)
For a neat line, apply masking tape above and below the joint, leaving a gap the width of your intended bead, typically 5 to 8 mm.
Step 5: apply the silicone
- Cut the nozzle at a 45-degree angle, slightly smaller than the gap.
- Hold the gun at a steady angle and apply a continuous bead, pushing the sealant into the joint.
- Work in one smooth movement along each side, rather than stopping and starting.
Step 6: smooth the bead
Dip a smoothing tool or finger in water with a little washing-up liquid and run it along the bead in one movement to create a concave finish. Wipe excess off the tool as you go. Remove masking tape immediately, pulling away from the bead.
Step 7: let it cure
Don't use the bath or shower until the sealant has cured, usually 24 hours or as the manufacturer says. Keep the room ventilated. Then empty the bath.
Common problems
- Sealant won't stick: the surface was damp or dirty; remove and redo.
- Gaps behind the sealant: very wide gaps may need a backing rod or foam strip first.
- Mould returns quickly: improve ventilation, run the extractor fan during and after showers, and wipe the seal dry.
- Bath moves: a loose bath may need its feet or frame adjusting before resealing.
Preventing mould
- use the extractor fan or open a window during and after bathing;
- squeegee or wipe surfaces after showering;
- clean regularly with a bathroom cleaner.
Choosing a sealant
Use a sanitary silicone designed for bathrooms, with mould inhibitors. Avoid general-purpose or decorator's caulk, which isn't waterproof enough for baths and showers.
When to call a professional?
If there's water damage below the bath, soft floors, or a persistent leak from pipes or the waste, call a plumber. Resealing won't fix leaking plumbing.
Frequently asked questions
How often should I reseal?
When the seal cracks, peels or gets mouldy, often every few years.
Can I put new silicone over old?
No. It won't bond properly. Always remove the old sealant.
Sources and further reading
Facts checked on 20 October 2026. Spotted an error? Tell us and we will correct it.