How to remove mould & mildew from a window sill

Condensation can occur on the inside of your windows. The condensation runs down the windowpane toward the windowsill, where it sets for an extended period. Excess moisture on windowsills provides a perfect breeding ground for fungus such as mould and mildew. Mould and mildew will stain and deteriorate the windowsill while filling the area with an unpleasant musty odour. Remove all mould and mildew growing on the windowsill as soon as possible to prevent the fungus from spreading.

Open the window during the mould and mildew removal process. Check for any mould and mildew growing on the rubber seal of the window.

Fill a spray bottle with white vinegar. Spray all visible mould and mildew with the white vinegar. Allow the vinegar to sit on the fungus for 10 to 15 minutes.

Spray white vinegar on a clean cloth. Wipe the surface mould and mildew off the windowsill -- as well as any other areas of the window with fungus growth -- with the white cloth. Vinegar is an all-natural deodoriser that will kill mould and mildew.

Mix 4 litres (1 gallon) of warm water with 200 gr (1 cup) of borax. Saturate a sponge in the mixture and wring out the excess liquid. Wash the windowsill with the sponge. Rinse the mixture off the windowsill with a clean, damp cloth. Wipe dry with a towel.


Alternatively, mix equal parts water and liquid dish soap in a small container. Dampen a cloth in the mixture. Wipe the mould off the windowsill with the damp cloth. Dampen a clean cloth in cool water. Wipe the mixture off the windowsill with the cloth. Dry with a towel.

Things You'll Need

  • Spray bottle
  • White vinegar
  • Cloths
  • Borax
  • Sponge
  • Towel
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About the Author

Amanda Flanigan began writing professionally in 2007. Flanigan has written for various publications, including WV Living and American Craft Council, and has published several eBooks on craft and garden-related subjects. Flanigan completed two writing courses at Pierpont Community and Technical College.