How to re-seal a bath or shower

• Time1 to 2 hours, plus curing
• DifficultyEasy to moderate
• CuringUsually 24 hours; check the cartridge

You will need

• Sanitary silicone sealant in white or clear
• Sealant gun and a sealant remover or scraper, from plumbing tools and chemicals
• Sharp utility knife or plastic sealant scraper
• Low-tack masking tape
• Sealant finishing tool, or washing-up liquid and water for a wet finger
• Mould and limescale cleaner, plus methylated spirit or a suitable surface cleaner, from cleaning products
• Clean lint-free cloths and kitchen roll

When does a bath or shower need re-sealing?

Re-seal when the sealant is mouldy and will not clean, has split or shrunk, or is coming away from the tiles or bath. Gaps let water get behind the bath or tray, which can damage walls, floors and ceilings below. If you notice staining on a ceiling below the bathroom, fix the seal and check for leaks from the waste and taps too.

Step 1: Remove the old sealant

1. Cut along both edges of the old bead with a sharp knife or scraper, taking care not to scratch acrylic baths, enamel or tiles.
2. Pull the bead away in strips.
3. Remove the remaining residue with a scraper and a sealant remover, following its instructions. New silicone will not bond properly over old silicone, so every trace must go.

Step 2: Clean and dry the joint

1. Treat any mould on the grout and surfaces with a mould cleaner, following the label, then rinse.
2. Wipe the joint with methylated spirit or a suitable cleaner to remove soap residue and grease.
3. Let the area dry completely. This is the most important step; ideally leave it overnight with the window open or the extractor running. Moisture trapped in the joint is a common cause of new sealant failing or going mouldy quickly.

Step 3: Fill the bath

Fill the bath with water before you apply the sealant. The weight of the water makes the bath settle slightly and opens the joint to its widest. Sealing it this way means the silicone is not stretched each time someone gets in. For a shower tray, standing in it while a helper seals is not practical, but make sure the tray is firmly bedded and does not flex. Leave the water in until the sealant has cured.

Step 4: Mask the joint

Run masking tape along the tiles and along the bath or tray, leaving an even gap where the bead will go, usually a few millimetres either side of the joint. This gives straight, clean edges and makes the job far easier for beginners.

Step 5: Apply the silicone

1. Cut the nozzle at a 45-degree angle, making the opening slightly smaller than the width of the gap. You can always cut more off.
2. Fit the cartridge in the gun and pierce the seal if required.
3. Starting in a corner, hold the gun at a consistent angle and push a steady, continuous bead along the joint. Keep moving at an even pace and avoid stopping.
4. Work one side at a time on large baths.

Step 6: Smooth and finish

1. Smooth the bead in one continuous pass using a sealant finishing tool or a finger dipped in water with a little washing-up liquid, following the cartridge advice.
2. Wipe excess sealant off the tool or your finger onto kitchen roll as you go.
3. Peel off the masking tape immediately, pulling it away from the bead at a low angle, before the sealant skins.
4. Do not touch the bead again once it begins to skin.

Step 7: Leave it to cure

Keep the area dry and ventilated, and do not use the bath or shower until the full cure time on the cartridge has passed, which is often around 24 hours but can be longer in cold weather or for wide beads. Then drain the bath.

Keeping the new seal looking good

Wipe the sealant dry after showers, run the extractor fan and clean regularly with a mild bathroom cleaner. Avoid harsh abrasives that scratch the surface, as scratches can hold dirt and mould. To understand which product suits which job, read silicone vs polymer vs acrylic sealant, and browse our adhesives, fillers and sealants.