How to re-seal a shower

Inspired by Shower Seal UK. This guide draws on the tutorial "How To DIY Re-seal a Shower with a Mold Resistant Sealant" from the UK-based Shower Seal UK channel. The tips on removing the old sealant cleanly and getting a neat finish with masking tape are the parts most people miss the first time they attempt it.

1. Stop using the shower and let everything dry

Don't try to re-seal a wet shower. The silicone won't bond properly to damp surfaces, and you'll end up with the same mould problem returning within weeks. Leave the shower unused for at least 24 hours before you start, ideally with the bathroom window open.

If the enclosure has persistent damp or ventilation problems, that's worth sorting before re-sealing - otherwise you're just treating the symptom.

2. Remove all the old silicone

This step takes most of the time and matters more than any other. Old silicone that isn't completely removed will prevent the new bead from bonding, and mould trapped underneath will come straight through.

Use a silicone remover tool or a sharp craft knife to score along both edges of the old bead and peel it away in strips. Work carefully - scratching tiles or the shower tray is easy if you're rushing.

Once the bulk is off, apply a chemical silicone remover gel and leave it to work for the time stated on the label. Then scrub off the residue with an abrasive pad. You're looking for completely bare surface - no grey smears, no sticky patches.

3. Clean and degrease the joints

Even once the old silicone is off, the surface needs cleaning properly. Wipe down the joint area with methylated spirits or isopropyl alcohol on a clean cloth. This removes any soap residue, body fat, and cleaning product that would stop the new sealant gripping.

Run your finger along the joint area once it's dry. It should feel clean and slightly rough, not slippery or waxy. Any staining or discolouration at this point is likely in the surface of the tile or grout, not something silicone will solve - a grout pen or sealer is better for that.

4. Tape either side of the joint

This is the step that separates a neat result from a messy one. Run masking tape along each side of the joint, leaving just the gap you want the silicone bead to fill. Keep the tape as straight as possible - it dictates the edges of the finished bead.

Press the tape down firmly so silicone can't bleed under it. Use painter's tape rather than standard masking tape if you have it - it releases more cleanly.

5. Apply the new silicone

Choose a bathroom-grade silicone labelled as mould-resistant. Anti-fungal or anti-mould formulas genuinely do last longer in a damp environment compared to standard silicone.

Cut the nozzle at a 45-degree angle to give a bead roughly the right width for your joint. Load the cartridge into the gun and apply a continuous, consistent bead along the joint in one steady pass. Try not to stop and start mid-run - it creates voids and bumps.

Hold the gun at a consistent angle and move at a steady pace. Faster movement makes a thinner bead; slower makes a wider one. Aim for a slight overfill - you'll smooth it back shortly.

6. Smooth and remove the tape

Wet your finger or a smoothing tool and run it along the bead in one continuous stroke, pressing gently to push the silicone into the joint and remove the excess. Don't keep going back and forth - it just picks the silicone back up.

Remove the masking tape immediately while the silicone is still wet, pulling it back at 45 degrees rather than straight up. Wait a few seconds for the bead to settle, then check the edges. Any small blobs can be carefully lifted with a damp cloth while the silicone is still fresh.

7. Allow to cure before using the shower

Leave the silicone to cure for at least 24 hours before using the shower. Many products need longer in a cold or poorly ventilated room. Check the instructions on the cartridge - curing times vary between manufacturers.

The silicone should be firm to the touch and not leave any residue on your finger before you expose it to water. Using the shower too early causes the sealant to lift at the edges.

When to call a handyman

Re-sealing a shower is well within most people's ability. If the grout is crumbling, the tiles are loose, or there are signs of water getting behind the wall, the problem is bigger than just the silicone and needs proper investigation before re-sealing. Richard can help diagnose what's going on and sort it properly.