Enter your zip to
find local pros.
Windows Resources

What To Do About Mold On Windows

Mold. It’s unsightly, it makes your home look dirty, and worst of all, it’s dangerous to your health—it’s even been found to cause a variety of respiratory problems. So what should you do if you discover mold growing on your windows? Most importantly, get started as soon as possible to clean it up and figure out why it might be forming in the first place, because mold only gets worse over time.

Here’s a 10-step attack plan to help you banish the harmful intruder and keep your windows mold-free in the future.

Find the cause. Molds are microscopic fungi that grow easily in moist, somewhat dark conditions. Molds can develop in bathrooms, under kitchen sinks, in places where water has leaked into walls or floors, or in insulation that has gotten wet. Mold on window sills can develop in and around window frames. This happens when the windows leak rain in from the outside, or when moisture condenses on the windows in a bathroom after a shower. If mold has developed around a window in your living room, bedroom, or basement, find out how water is getting into the frame. If you notice mold around windows in the bathroom, the problem may be as simple as a lack of ventilation.

Remove the window and clean or replace the frame and fix the leaks. If mold has gotten into the window frame, you will need to remove the window and have the frame cleaned or replaced.  Remove all wet insulation or framing and thoroughly dry any framing that’s left in place. Then seal up the leaks around the window and frame to prevent the problem from reoccurring.

Check the roof and gutters. If you didn’t see any obvious window leaks, there’s a chance that your roof has a leak or that your gutters are backed up, which can send water down into your home and out through the window frames. Check the roof and gutters thoroughly to make sure they’re not creating the problem.


Redirect water away from your home. Basement windows may be getting wet because they are too close to the ground, and the ground gets too wet when it rains or snows—or even when someone waters the lawn.  Once the window has been fixed, drain water away from the home and the downstairs windows. You can also protect your downstairs windows with a window well that can help prevent water from seeping into your windows and growing mold. Water condenses on windows especially in the winter, then drips down into window frames, where it can cause mold. Sometimes ice forms on the inside of windows then melts and leaks into the window frames. Put a towel along the bottoms of the frames right next to the glass to absorb the water before it penetrates the frames.

Reduce humidity and moisture in the bathroom. If your bathroom windows are moldy, most likely it’s because there’s not enough ventilation. Always run the fan in the bathroom when bathing, and especially when showering. Leave a window open as well, and keep the door to the bathroom open after your shower so that there are several ways for steam to exit the room rather than condense on the windows. If your bathroom doesn’t have a ceiling fan, position a small portable fan on the floor or counter so it can circulate the air and help dry it out.

Use bleach to clean up the mold. There are several enzyme-based products on the market, but a diluted solution of bleach and water works best for eradicating mold. The U.S. Centers for Disease Control recommend using a mixture of one cup of bleach to one cup of water. Never mix bleach and ammonia together! Wear gloves and a face mask to reduce the chances of inhaling the bleach fumes, and either spray the cleaning mixture on the mold or use a sponge to wipe the mold away. Continue to spray and wipe, rinsing out the sponge in the bleach mixture until you’ve gotten rid of all signs of mold.

Monitor your windows. Mold is notoriously difficult to destroy. Once you’ve cleaned your windows and addressed the source of the problem, keep a watchful eye on your windows to make sure the mold doesn’t return. If you notice water puddling on a windowsill or condensing on the window frames, wipe them up immediately.

How have you banished the mold in your home, and which method worked best for you? Share with us in the comments below! If you have more issues than just mold, maybe you should consider window replacement from a local contractor.

Find today's best prices for your
home improvement project.