How to replace silicone around a bath or shower
Cracked, detached or mould-stained silicone can let water reach the edge of a bath, shower tray or worktop. Replacing it is a realistic DIY job when the surfaces are sound and the leak is confined to the seal. Applying a fresh bead over old silicone is not a lasting repair because new sealant will not bond reliably to contaminated silicone beneath it.
First rule out movement, failed grout, leaking pipework and damaged boards. If the tray moves under weight, tiles are loose or the wall feels soft, stop using the shower and repair the underlying problem before resealing.
Remove every part of the old bead
Use a plastic scraper or suitable sealant-removal tool to cut along both edges and lift the main bead. Keep sharp blades shallow and away from acrylic baths, tray coatings and waterproof membranes. Remove remaining film patiently; even a thin residue can spoil adhesion.
- Protect the plughole so old silicone cannot enter the waste.
- Do not lever against a tile edge or flexible acrylic surface.
- Use a remover compatible with the bath, tray, tile and grout.
- Vacuum loose material rather than washing it into the joint.
Clean, inspect and dry the joint
Clean soap, grease and remover residue using products approved by the sealant manufacturer, then allow the joint to dry completely. Examine the gap with good light. Dark staining on the surface may be manageable, but soft plasterboard, swollen timber, loose tile adhesive or persistent moisture means the leak has progressed beyond a cosmetic seal.
Prepare the bath and choose the sealant
Use a sanitary silicone intended for bathrooms and compatible with the materials. Follow the product's stated joint size, primer requirements, temperature range and curing time. If the bath manufacturer recommends filling the bath before sealing so the rim sits under working load, follow that instruction and keep the water in place through the initial cure.
Masking tape can define both edges of the bead. Keep the gap wide enough for sealant to bridge and flex; a paper-thin smear is unlikely to tolerate movement.
Apply one continuous, controlled bead
Cut the nozzle slightly smaller than the required bead and hold the gun at a consistent angle. Push or pull steadily without stopping in corners. Tool the bead once with a proper profiling tool, pressing it against both sides of the joint, then remove masking tape before a skin forms. Avoid repeated finger smoothing or household detergent unless the product instructions explicitly allow it.
Let it cure and test the repair
Keep the area dry for the full cure period printed on the cartridge; surface skinning is not full cure. Afterwards, run water normally and inspect the adjoining room, ceiling below and access panels. If staining returns, the source may be a waste, supply, grout or waterproofing failure.
Useful job post: 'Shower tray in a Cork apartment has split silicone along the back corner and a small stain has appeared on the skirting outside. The tray has slight movement when stepped on, so I have stopped using it and have not resealed over the old bead. Photos show the full enclosure, failed joint and stain. Please inspect the tray support and waterproofing, repair the cause and apply new sanitary silicone.'
Frequently asked questions
Can I put new silicone over old silicone?+
It is unlikely to form a durable seal. Remove the old bead and residue, clean the surfaces and let the joint dry before applying new silicone.
How long before I can use the shower?+
Use the curing time on the exact sealant cartridge. Humidity, bead size and temperature affect curing, so do not rely on a generic time.
Why does bathroom silicone keep splitting?+
Movement in the bath or tray, poor preparation, an undersized bead or incompatible sealant can cause repeated failure. Fix movement before resealing.
When is failed silicone a professional repair?+
Get help when surfaces move, tiles are loose, boards feel soft, water reaches another room or the leak continues after a correctly cured seal.
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