How to Kill Mold on a Window Sill

Mold is a fungi that grows in damp or humid areas. It can grows on just about anything, including your window sill. A window sill can be particularly vulnerable because of condensation on the window. Water can also leak in through the window frame. With a few guidelines and materials, you can kill mold on a window sill.

Things You'll Need

  • Spatula
  • Chlorine bleach
  • Laundry detergent
  • Water
  • Sponge
  • Mold killing product
  • Wood cleaning product
  • Sandpaper
  • Wood finish
  • Paint

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Clean off the window sill. Remove any dirt, cracked paint or other debris. Scrape off any visible mold with a spatula. Use a non-metallic spatula to avoid scratching the wood.

Create a solution to kill the mold. Mix 1/2 cup bleach and 1/2 cup laundry detergent with one gallon water.

Test the solution on a small portion of the window sill to see if it has any adverse effects. If the wood changes color, use a solution of water and detergent only.

Scrub the solution into the mold with a sponge. Keep scrubbing until the mold is gone.

Allow the window sill to dry completely. Open the window if it is a dry, non-humid day. Scrub and let the window sill dry again if mold persists.

Stubborn Mold Treatment

Apply a commercial mold-killing product available at most hardware or home improvement stores. Scrub the window sill with a wood-cleaning product.

Sand the window sill to get at the mold's roots.

Apply a wood finisher or repaint the window sill after sanding. Make sure all the mold is gone before painting. Mold will grow under paint.

Tips & Warnings

  • Attack the mold as early as possible. Avoid letting water stand on the wood for too long. Water can damage the wood.
  • Be careful working around mold. Wear old clothes, rubber gloves, eye goggles and a painter's mask. Mold can be toxic.


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