Old silicone sealant in the bathroom is one of those things people ignore for years — until mould appears underneath or water starts seeping behind the shower tray. The job takes a few hours but requires patience and proper surface prep.
When does silicone sealant need replacing?
Clear signs: black or green discolouration (mould that has penetrated the sealant), cracking or pulling away from the surface, loss of flexibility, or a persistent smell despite cleaning. Even sealant that looks reasonable usually loses its seal after five to seven years.
What you will need
- A silicone removal tool or Stanley knife
- Silicone residue remover (isopropanol-based)
- Sanitary silicone with a fungicide (not general-purpose building sealant — it is not suitable for wet areas)
- A sealant gun
- Masking tape
- A damp finger or smoothing tool
How to replace bathroom silicone — step by step
1. Remove the old sealant. Score along both edges with a knife and peel it away as a strip. Scrape off any residue carefully — you do not want to scratch enamel baths or acrylic shower trays. Then degrease both surfaces with isopropanol and let them dry completely.
2. Apply masking tape. Run tape along both sides of the joint. This gives you a clean straight line and keeps excess sealant off the tiles. Skipping this step is the most visible sign of an amateur job.
3. Apply the sealant. Hold the gun at 45 degrees and run a continuous bead in a single pass without stopping. The joint should sit slightly proud of the surface.
4. Smooth it. Wet your finger or use a profiling tool and draw it along the joint in one uninterrupted stroke. Remove the masking tape immediately after smoothing, before the sealant starts to skin over.
5. Curing time. Keep the area dry for at least 24 hours — 48 hours for deeper joints. Check the cartridge label; cure times vary by product.
Common mistakes to avoid
- Applying new sealant over old — mould grows straight through and the new layer will peel off within months
- Skipping degreasing — sealant will not bond to a greasy or damp surface
- Using general-purpose building silicone instead of fungicide-rated sanitary sealant
- Getting the joint wet too soon — it cracks at the first shower
When to call a professional
If mould has spread into the grout, under tiles, or into the wall structure, replacing the sealant will not solve the underlying problem — the source of moisture needs to be found and fixed. This is common in Warsaw apartments where the original waterproofing was never done properly. Leave a request in the contact form and we will assess the situation and tell you what needs to happen.