Why Do Window Frames Have Holes At The Bottom? Here's What They're For

Holes on the exterior of your home are often a bad thing — they allow for moisture and pests to enter your home. That's why it's important to seal your door gaps and other openings on your home's exterior. But there's a specific type of hole in the bottom of many window frames that's there for a very good reason. They're called weep holes, and they let water drain out of the window frame instead of accumulating and causing damage. The holes also minimize issues caused by pressure differences because they help equalize air pressure in the window frame. 

Window exteriors endure all types of weather, often with moisture involved. Rainstorms, snow, and even humidity can cause moisture to form inside your window frames, so weep holes are especially helpful in climates with frequent bouts of this type of weather. Water seems to find a way inside windows, even if you have a screen in place. Strong winds could force rain inside the frame, condensation can accumulate, overspray from your sprinklers or garden hose, and water splashes from kids playing could all contribute to collected moisture. If the water doesn't drain out, it can settle inside the hollow chambers of the frame, where it can cause deterioration and damage. Mold and mildew growth are also a concern. Weep holes eliminate that problem by directing water out of the frame.

Weep holes are mini drainage systems for windows. The holes on the frame allow water to exit easily through a channel that directs the water outside. A window can have one or more weep holes, usually located on the bottom of the window frame since that's where water naturally collects. It's common for weep holes to have little flaps on the outside of the window to keep wind and rain from blowing back up through the channel. Water flowing down through the weep hole pushes the flap open so it can escape, which encourages the moisture to only travel in one direction.

Not all windows have weep holes. They're typically only featured on windows made of vinyl, fiberglass, or metal because the frame construction includes hollow spaces where water can get trapped. Weep holes are also more common on certain types of windows, including sliding and double-hung windows, where moisture is more likely to collect in the track or frame.

The immediate benefit of weep holes is eliminating water that would normally pool inside the frame or track. By keeping this moisture from backing up into your home or seeping deeper into the frame, where it can cause structural damage, these drainage holes help your windows last longer when they're properly maintained. Keeping water out of the frames also helps reduce condensation that forms on windows and minimizes mold and mildew growth. It could even keep mosquitoes and other pests away by eliminating an attractive source of water. To get these benefits, avoid covering the holes when caulking your window.

Maintenance mainly focuses on keeping the weep holes open so water can drain freely. The drainage channels can become clogged with dirt and outdoor debris, which keeps the water from flowing and allows it to build up along your windows. Sometimes you can see gunk gathered around the opening. If your windows have flaps covering the opening, use a flathead screwdriver or a similar device to flip open the covering and look for debris. You can also test how well it's working by pouring water into the frame and watching for it to drain out of the frame.

Even if the weep holes seem to be working, cleaning them at least once or twice per year prevents a problem. An old toothbrush or cleaning brush works well to scrub away visible debris near the openings, and compressed air helps push debris through the drainage channels easily. It can also help to pour water through the hole or squeeze water into the hole with a syringe to wash away any remaining debris. If you have anything stuck in the channel, a piece of wire, a pipe cleaner, or a flexible straw-cleaning brush could help push the blockage through the hole. The process is easy enough to perform when you clean your windows routinely.