Cleaning Tips4 min read

How to Remove Mould from Caulking — Toronto Guide 2026

How to remove mould from bathroom and kitchen caulking in your Toronto home. When cleaning works and when you need to replace the caulk.

M
Maidless

How to Remove Mould from Caulking

Mould growing in caulking is a common bathroom and kitchen problem caused by the moisture that the silicone or latex caulk absorbs over time. There are two situations: surface mould that can be removed with bleach treatment, and deeply embedded mould that has penetrated the caulk and cannot be fully removed without replacement. The difference is visible — surface mould is on the caulk face; embedded mould shows as dark colouring throughout the caulk body.

Surface Mould Treatment (Removable)

If the mould is on the surface of the caulk and hasn't penetrated deeply:

  1. Apply undiluted bleach to the mouldy caulking using a cotton ball or folded paper towel — place it directly on the caulk and saturate it
  2. Allow to work for 30 minutes to 1 hour. For stubborn mould: cover the bleach-soaked cotton ball with plastic wrap to prevent evaporation and allow 2–3 hours.
  3. Scrub with an old toothbrush
  4. Rinse with water and dry
  5. Repeat if any mould remains

Hydrogen Peroxide (Alternative to Bleach, Safer for Coloured Tiles)

  • Apply 3% hydrogen peroxide (drugstore hydrogen peroxide) to the mouldy caulk
  • Allow 10–15 minutes
  • Scrub with a toothbrush and rinse
  • Less harsh than bleach but still effective on surface mould

When to Replace the Caulk (Embedded Mould)

If the mould is embedded throughout the caulk body (visible as dark colouration when you look at the caulk from the side), cleaning treatments improve the appearance temporarily but the mould always returns because it's growing through the entire caulk. The correct fix is recaulking:

  1. Remove the old caulk completely with a caulk removal tool or a utility knife — be careful not to scratch tiles
  2. Clean the gap with bleach, allow to dry completely (24 hours minimum)
  3. Apply new 100% silicone caulk (not latex) in a continuous bead — silicone is more mould-resistant than latex
  4. Smooth with a wet finger and allow to cure per product directions (typically 24 hours before water exposure)

Preventing Mould in Caulking

  • Keep the shower/tub area dry — squeegee or wipe down after each use
  • Run the bathroom exhaust fan during showers and for 15 minutes after
  • Apply a caulk sealant or mould-resistant spray to the caulk annually

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