Window sills collect more grime than most surfaces — outdoor dust, pollen, dead insects, condensation, and paint chips all accumulate in the corners and tracks. Indoor sills can also develop mould from condensation on cold windows in Toronto winters.
Basic Clean
- Use a dry brush or vacuum with the crevice attachment to remove loose debris, dead insects, and dust from the corners and tracks
- Mix warm water with a few drops of dish soap in a spray bottle
- Spray and wipe with a microfibre cloth
- Use a cotton swab or old toothbrush to reach into the corners and sliding track channels
- Dry thoroughly — moisture in the sill tracks promotes mould growth, especially in winter
Removing Mould from Window Sills
- Mix equal parts white vinegar and water in a spray bottle
- Spray the mouldy area and let sit for 10–15 minutes
- Scrub with a stiff small brush or old toothbrush
- Wipe clean with a damp cloth and dry completely
- For persistent mould on non-porous vinyl or painted surfaces: a diluted bleach solution (1 tablespoon bleach per litre of water) kills mould spores more effectively than vinegar
Exterior Window Sills
Exterior sills are exposed to weathering — bird droppings, pollen, algae, and paint erosion. Scrub with warm soapy water and a stiff brush. For algae or green moss growth: a diluted bleach spray (1:4 bleach:water), left for 10 minutes then rinsed, removes it effectively. Repaint any chipping paint promptly to prevent moisture penetration and rot in wood sills.
Tips
- Interior window condensation is the main cause of mould on interior sills — improve ventilation, use a dehumidifier, or add window insulation film to reduce it
- Vinyl sills: avoid abrasive cleaners that scratch the surface
- Stone or marble sills: use pH-neutral cleaner only — vinegar and bleach etch natural stone