How to Get Rid of Mold on Your Window Sills [7 Methods]

A mixture of tea tree oil and water has antifungal properties that will kill mold on contact. Spray the solution onto your window sill, let it soak for 30 minutes, then wipe away the mold. You can also use a commercial mold killer, an ammonia-based cleaner, or hydrogen peroxide to quickly and effectively kill mold on your window sill. If you wish to avoid using chemicals, you can make your own mold killer spray from vinegar and water. Next, use a dehumidifier to dry out the air in damp rooms and kill mold. Finally, remember to steer clear of soapy water and bleach cleaners—they aren’t effective at killing mold on window sills.

How to get rid of mold on window sill

Why is Mold Growing On Your Window Sill?

Mold is caused by moisture. So, it is commonly caused by a leaky window that allows water to dampen the window sill. However, condensation on your windows is also a frequent cause of mold. Water condenses on your windows when warm, humid air comes into contact with cool glass. Bathroom and kitchen windows commonly become wet with condensation that trickles down onto your window sill. Then, mold grows on the sill.

  • A leaky window can allow moisture to collect on your window sill and encourage mold growth.
  • Warm, humid air contacting cold glass can cause condensation, which triggers mold growth.
  • Bathroom and kitchen windows are common breeding grounds for mold.
  • Cold outdoor weather encourages more window condensation, which can lead to increased mold growth.

If you live in a region with cold winters, mold commonly grows during the colder months. This occurs because the warm air in your home comes in contact with the cold glass. Then, condensation forms and drips down onto the window sill. Mold grows quickly in these damp areas. So, if you’re battling winter mold, you’re not at fault.

Is Black Mold on Window Sills Toxic?

The mold growing on your window sill can be harmful to your health. Mold spores can trigger allergic reactions and skin irritation. If you are experiencing these symptoms and have mold growing on your window sills, it may be worth visiting an allergist for testing. They can help determine if you have a mold allergy.

  • Mold growing on your window sill can be harmful to your health.
  • The most common side effects of mold exposure are allergy symptoms and skin irritation.
  • Mold will also destroy the window sill it is growing on.
  • If you don’t kill mold, it can spread through your home.

In addition to health concerns, mold can also destroy the wood of your window sills. Mold is a fungus. As it grows, it devours the surface it’s growing on. If left unchecked, mold can eat through your wooden window sill. It can also spread to other areas in your home, including inside your walls and ceilings.

7 Ways to Kill Mold Growing on Your Window Sills

Before you begin any treatment for window sill mold, it’s essential to wear gloves and a dust mask. This will prevent you from inhaling mold spores. It will also protect against the compounds and chemicals that you use to kill mold. Any sponge or cloth you use to scrub or wipe away mold should be thrown away immediately afterward. This will help prevent mold spores from spreading to other areas of your home.

Tea Tree Oil

You can kill mold naturally by using tea tree oil. Simply mix 3 tablespoons (45 ml) of this tea tree oil in 2 cups (475 ml) of water. Mix the ingredients together in a spray bottle. Then, spray the mixture on the mold. Allow the mixture to soak for 30 minutes. Then, wipe the mold away with a sponge or scrubbing pad. Studies have shown that tea tree oil is a powerful natural antifungal that can kill mold on contact. It is our top natural remedy for mold growing on your window sill.

Commercial Mold Spray

This powerful mold killer spray will penetrate painted surfaces and kill mold. Because it is engineered without bleach, it is safe for use without damaging your window sill’s appearance. Follow the manufacturer’s instructions to quickly and completely kill mold. Unlike glass cleaners, a mold killer will penetrate deeply enough to kill mold spores in wood and prevent mold from growing back.

Ammonia-Based Cleaners

Ammonia is a fantastic antifungal that kills mold fast. This ammonia-based cleanser is a great choice for moldy window sills. Spray or wipe the ammonia onto moldy portions of your window sill, then wait 15–30 minutes for the ammonia to destroy the mold. After waiting, you can clean away the mold residue. For your safety, never mix bleach with an ammonia cleanser. Doing so will produce toxic chlorine gas that is harmful to your health.

We earn a commission if you click this link and make a purchase at no additional cost to you.

Hydrogen Peroxide

Hydrogen peroxide will kill mold on your window sill in 10 minutes. Simply purchase 3% hydrogen peroxide from a local drug store. Then, spray or douse the mold growth with the hydrogen peroxide. Hydrogen peroxide won’t damage most paint, but, it’s not a bad idea to dab it on a small painted area to make sure it won’t cause any paint discoloration. Once you know it’s safe, you can use the hydrogen peroxide to kill mold fast.


Vinegar is not as strong at killing mold on porous surfaces as tea tree oil. However, you may be surprised at how useful vinegar is for killing mold. You can use undiluted white vinegar, or make a 50/50 mix of vinegar and water. If your window sill has a thick coat of paint, vinegar may do the trick. If the mold returns, it’s time to use tea tree oil or another stronger antifungal.

Use a Dehumidifier

Mold thrives in humid environments. If certain rooms in your home are prone to growing mold on the window sills, place this dehumidifier in the room. Run the dehumidifier for at least 12 hours each day, but you can leave it on 24/7 if you want. By drawing moisture out of the air, the dehumidifier will help to kill mold and prevent it from growing back.

Avoid Soapy Water and Bleach

Hot, soapy water and bleach are both ineffective mold killers that are not worth your time. Soap and water have very weak antifungal properties that may temporarily reduce the appearance of mold but won’t prevent it from coming back. Bleach is only effective for killing mold on non-porous surfaces, such as glass and plastic. Plus, bleach can discolor your paint. Make sure to avoid using bleach for mold on your window sill.

How Do You Get Rid of Black Mold on Wood Window Sills?

The best ways to permanently get rid of mold growing on your window sills are:

  • Spray a mixture of tea tree oil and water on the mold and allow it to soak for 30 minutes.
  • Use a commercial mold killer spray designed for use on painted and porous surfaces.
  • Spray mold with an ammonia-based cleanser and allow it to soak for 15–30 minutes before cleaning.
  • Apply hydrogen peroxide to the mold growth and let it sit for 10 minutes.
  • Spray white vinegar on the mold and allow it to soak for 30 minutes—if mold grows back, use a stronger cleanser.
  • Place a dehumidifier in the room and run it for at least 12 hours per day—dry air kills mold and discourages mold growth.
  • Avoid using bleach, as well as soap-and-warm-water mixtures. Both these fixes are ineffective at killing mold on window sills.

Because black mold can cause allergic reactions and health problems, it’s important to attack it quickly with a powerful solution. This way, you can stop the growth of mold before it spreads to other areas of your home.

Does vinegar kill bed bugs?

Does Vinegar Kill Bed Bugs? [3 Reasons it Won’t Work]

How to get rid of mushrooms in yard

How to Get Rid of Mushrooms in Your Yard [6 Amazing Methods]