DIY: resealing silicone around the basin, bath and shower (removal, cleaning, application, cure time)

The joint between the bath, shower tray or basin and the wall moves slightly with use and temperature, so it is sealed with a flexible material such as silicone rather than grout. Over time the silicone goes mouldy or comes away, letting water get behind the tiles.

1) Removing the old silicone

GE recommends using a utility knife or scraper to cut and lift the old sealant, then cleaning the residue with rubbing alcohol and letting the surface dry fully before applying new sealant1.

1. Cut carefully along both sides of the silicone bead so you don't scratch the bath or enamel.
2. Pull the old bead out by hand, then scrape off the remains with a plastic scraper.
3. Wipe with rubbing alcohol to remove the thin remaining film and grease.
4. Let the joint dry completely; the surface must be clean and dry, with no soap film, dust or grease1.

2) Applying the new silicone

1. (Optional) apply masking tape along both sides of the joint for a straight line.
2. Cut the nozzle at 45°, puncture the inner seal, load the cartridge into the gun, and apply steady pressure1.
3. Run the nozzle along the joint in one continuous movement.
4. Tool the bead immediately after applying1, with a smoothing tool or a gloved finger dipped in a little soapy water.
5. Remove the tape straight after tooling, before a skin forms.

3) Drying and curing

According to GE, its silicone becomes water-resistant in about 30 minutes and cures within 24 hours, and it must cure fully before being exposed to water1. Times vary between products; always check the product you are using.

4) Can silicone be painted?

No. GE states that paint won't stick to 100% silicone, whatever the paint, and that primer doesn't help; if you need to paint the joint, choose a product labelled "paintable"1.

5) Which type to buy?

• For bathrooms and kitchens: sanitary silicone with mould resistance.
• Don't use cement grout at changes of plane and around the bath; these need a flexible sealant. See the grout guide.
• If water has already got behind the tiles (hollow-sounding tiles or damp on the wall behind), the problem is bigger than the silicone. See waterproofing under tiles.