How to Re-Seal a Shower
Published 17 June 2026 · Bridgnorth Bathroom Fitters
Failing silicone is one of the most common bathroom issues. Cracks, mould or sealant pulling away from the wall lets water reach the structure behind, which is what causes leaks, ceiling stains downstairs, and ultimately serious damage if ignored.
Replacing silicone is a job a careful DIY-er can manage. Here’s how to do it properly.
When silicone needs replacing
Look for:
- Black mould inside the silicone that doesn’t clean off
- Visible cracks along the silicone bead
- Sealant pulling away from one surface (wall or bath)
- Yellowing or discoloration of originally-white silicone
- Soft, gummy texture when pressed (silicone hardens over years; new silicone is firm)
- Visible gaps at corners or joints
Don’t wait until water visibly leaks through — by then, the structure behind is often already damp.
What you need
Tools
- Sharp Stanley knife or specialist sealant remover
- Silicone removal tool (looks like a small spatula)
- Old toothbrush or small stiff brush
- White spirit or methylated spirit
- Clean cloths
- Caulking gun (about £10)
- Masking tape
- A spatula or smoothing tool (or your finger with washing-up liquid)
Sealant
- Sanitary silicone (specifically labelled “sanitary” or “bathroom”) — contains anti-mould additives. Don’t substitute kitchen sealant or general-purpose silicone
- Around £8–£15 per cartridge for a quality product
- Colour matched to the existing — usually white, sometimes grey, sometimes transparent
We recommend Dow Corning, Geocel or Soudal sanitary silicones. Avoid cheap multi-purpose silicones — they fail faster and grow mould easier.
Step-by-step
1. Remove the old sealant completely
This is the most important step. New silicone won’t bond properly to old silicone — they’re chemically distinct and the bond will fail. Every trace of old silicone needs to go.
Use the Stanley knife to slice along the top and bottom of the old bead, then peel out the strip. A silicone removal tool helps pull away stubborn sections.
Be patient. A full bath surround can take 20–30 minutes of careful work. Rushing leads to either incomplete removal (new silicone failing) or knife slips that damage surfaces.
2. Clean the surfaces thoroughly
Once the bulk of the old silicone is removed, there’s usually a thin residue. Use a stiff brush to dislodge it, then wipe down with white spirit on a clean cloth.
The surfaces must be completely clean and dry before applying new silicone. Any moisture, soap residue, mould or old silicone fragments will compromise the bond.
Let the area dry fully — at least 30 minutes, ideally a couple of hours.
3. Apply masking tape
This is the trick that produces professional-looking results. Apply masking tape on both sides of where the silicone bead will sit, leaving a gap of about 5mm (the width of your intended sealant bead).
Press the tape firmly down. The tape stops silicone smearing onto the surrounding tile and gives you a clean, straight edge.
4. Cut the nozzle
Cut the cartridge tip at an angle, about 5mm from the tip. This produces a bead about 5mm wide — the right size for most bathroom joints. Bigger beads tend to look messy; smaller ones don’t bridge the gap properly.
5. Apply the silicone
Hold the caulking gun at 45° to the joint. Squeeze the trigger steadily and move along the joint at consistent speed. Aim to apply the sealant in one continuous bead — stops and starts show up.
For long runs (a full bath edge), don’t try to do it all in one go if you’re not experienced. Work in 600–900mm sections.
6. Smooth the bead immediately
Within 5 minutes of applying, smooth the silicone with a wet finger or spatula. Run smoothly along the bead in one motion. A small amount of washing-up liquid in water (or use saliva — old plumber’s trick) helps your finger glide without dragging the silicone.
Don’t go back over the bead repeatedly — you’ll create marks. One smooth pass per section is ideal.
7. Remove the masking tape
Critical: do this while the silicone is still wet (within 5 minutes of smoothing). Pull the tape away at 45° from the silicone, slowly and steadily. This produces the crisp, straight edge that gives a professional finish.
If you wait until the silicone has skinned, the tape pulls the edge off the bead. Wet tape removal is the right time.
8. Let it cure
Sanitary silicone typically:
- Skins in 5–15 minutes (no longer tacky)
- Cures fully in 24 hours
Don’t use the shower for at least 24 hours. Hot water and steam during cure can cause the sealant to bubble or fail.
Common mistakes
Leaving old silicone in place
“I’ll just put new silicone over the old” — doesn’t work. The new silicone has nothing chemical to bond to and will fail within months.
Not cleaning thoroughly
Even a thin residue of soap or old silicone affects adhesion. Clean properly.
Wet surfaces
Silicone needs to bond to dry material. Showering before resealing, or sealing on a damp day, compromises the bond.
Too thick a bead
Big sausages of silicone look unprofessional and trap moisture against the wall. 5mm bead is plenty.
Not removing masking tape promptly
Skinned-over silicone bonds to the tape and tears when the tape is removed.
Using kitchen silicone in bathrooms
Kitchen silicone lacks anti-mould additives. It will mould within months in bathroom conditions.
Specific situations
Re-sealing around a bath
The most common DIY resealing job. Fill the bath with water before resealing — the weight ensures the bath sits at its full operational position and the seal stays intact when the bath is in use.
Apply silicone with the bath full, let cure for 24 hours, then drain.
Re-sealing the corner where two walls meet
Particularly prone to cracking because of slight wall movement. Use generous sealant and consider sanitary-grade silicone with high elasticity for these joints.
Re-sealing around a shower tray
Similar to bath sealing — load the tray with water if it’s a stand-in tray (less applicable for stone resin trays). For wet rooms and walk-in showers, the silicone joint is at the floor-wall junction.
Re-sealing around a basin
Apply with the basin in its installed position. Don’t put weight in it during cure.
When to call a professional
DIY re-sealing is reasonable when:
- The job is small (single bath edge, single shower joint)
- The underlying structure looks fine — no damp staining, no movement
- You have the patience for thorough removal of old sealant
Call a professional when:
- You see damp staining behind the silicone — suggests longer-term water ingress
- The substrate behind (tile, wall) has come loose or damaged
- Multiple joints need replacing and you’d rather have it done properly
- You’ve tried and the result doesn’t look right
For our customers, post-installation silicone replacement within the guarantee period is something we’ll typically come back and do.
How often to re-seal
Sanitary silicone in good conditions lasts 5–10 years. In high-use bathrooms (master bathrooms used daily, family bathrooms with kids) it might need attention every 3–5 years.
Routine inspection every 6 months catches problems early.
Sealant vs grout — when each is right
A common confusion. The rule:
- Silicone sealant for joints between different materials, or where there’s potential movement: tile-to-bath, tile-to-tray, corner of two tiled walls, floor-to-wall junction
- Grout for joints between tiles (rigid joints, no expected movement)
Silicone in tile-to-tile joints is wrong — it doesn’t last and doesn’t look right. Grout in tile-to-bath joints is wrong — it cracks immediately because of the movement.
If your previous bathroom has grout where silicone should be (or vice versa), the right time to fix this is when you’re already doing maintenance work.
FAQ
Can I paint over silicone? No. Paint doesn’t bond to silicone — peels off immediately.
What about silicone colours other than white? Available — grey, beige, black, clear. Match the tone of your tile and joint.
Is “mould-resistant” silicone worth the extra cost? Yes. Sanitary silicone with anti-mould additives lasts visibly longer in bathroom conditions. The cost difference (a couple of pounds) is well worth it.
Can I use silicone outside? Some grades are external-rated, others aren’t. Check the label.
Need help with re-sealing?
If you’d like a professional re-seal job done — particularly around a shower where leaks could be developing — get in touch. Quick, neat work, properly done.