Look closely at the bottom of most windows and storm windows and you will find a few small slots or holes. Those are window weep holes, and they have one job: letting water that gets into the window frame drain back outside. When they clog with dirt, bugs, paint or caulk, that water has nowhere to go. Obstructed weep holes are a common finding when we inspect windows and storm windows in Fargo, Moorhead and West Fargo homes, and they are one of the easiest window problems to fix. Here is what they do, why they matter here, and how to keep them clear.

What window weep holes do

No window is completely watertight. Wind-driven rain, melting snow and condensation all find their way into window tracks and frames. Manufacturers plan for this with a drainage system, often called a weep system. Water collects in the bottom of the frame or track and drains out through weep holes on the exterior.

According to the American Architectural Manufacturers Association (AAMA) window care guide, these drainage pathways must be kept clear and clean for the window to work correctly. Weep holes are usually small slots or holes on the outside face of the bottom of the frame.

Exterior storm windows have their own weep holes or gaps at the bottom of the storm frame. The U.S. Department of Energy’s Building America Solution Center says storm windows should be sealed at the top and sides but left unsealed at the sill, with weep openings that are never caulked, because they provide drainage. Weep openings are required for ENERGY STAR certified storm windows.

Why weep holes matter in Fargo-Moorhead

Storm windows are common on older homes in our area, and many newer homes have vinyl or aluminum sliding and single-hung windows with weep systems. Our weather puts both to work:

Wind-driven rain pushes water into tracks and frames during summer storms.
Snow and ice melt against windows in spring and during midwinter thaws.
Indoor moisture in winter. The DOE notes that condensation between a storm window and the main window forms when warm, moist indoor air leaks past the main window and reaches the cold storm glass. That water, or frost when it melts, runs down to the bottom of the storm frame and needs a way out.

When weep holes are blocked, water sits in the track or on the sill. The DOE warns that trapped water can accumulate within the frame and eventually damage the framing, sheathing, insulation and other building materials.

Signs your weep holes are blocked

Water standing in the window track after rain or after cleaning the window
Dirt, dead insects, leaves or cottony seeds packed in the bottom of the track
Paint, caulk or sealant covering the weep slots on the outside of the frame
Water stains, peeling paint or soft wood on the sill below a storm window
Moisture or frost that collects between a storm window and the main window and does not dry out

What obstructed weep holes mean in an inspection report

During a home inspection, we look at the bottom of windows and storm windows for weep holes that are plugged with debris, painted over or caulked shut. When we find them, we note it in the inspection report and recommend removing the obstructions so the window can drain properly.

On its own, this is a maintenance item. It becomes more important when we also find signs that water has been trapped, such as soft or rotted sill wood, staining on the interior trim or sill, or moisture damage below the window. Those findings point to a repair, not just a cleaning, and we will call them out separately.

If you are buying a home, clean the weep holes after you move in and check the sills under any storm windows. If we report rot or water damage at a window, get a repair estimate during your inspection contingency.

How to clean window weep holes

The DOE’s Building America Solution Center recommends a simple test and cleaning process:

Test first. Pour a glass of water into the window track or mist the outside of the window with a hose. Some water should run out of the weep holes. If it doesn’t, or if you can see debris, it is time to clean.
Clear the track. Vacuum loose dirt from the track with a brush attachment, or sweep it with a dry paint brush.
Open the holes. Gently clear each weep hole with a pipe cleaner, a small bottle brush, a straw brush or a piece of stiff wire. Work from the inside of the track where you can, and try not to push debris deeper into the channel.
Flush and retest. Run water through the track again and confirm it drains outside. Compressed air blown from the inside can help clear a stubborn channel.
Remove caulk or paint. If the slots were sealed over, carefully cut the sealant away with a utility knife or putty knife. Do not use harsh solvents on vinyl frames. Pella, for example, warns that mineral spirits and similar solvents can soften vinyl.

A few cautions:

Never caulk or seal weep holes, and do not caulk across the bottom of an exterior storm window. As This Old House carpenter Tom Silva puts it, caulking the bottom creates a dam, and the trapped water can rot the sill.
Don’t force the flaps. Many weep holes have small covers or baffles. AAMA notes they should move freely, so clean around them gently rather than prying them off.
Skip oil-based lubricants in the tracks. AAMA warns they can damage weep holes.

How to keep weep holes working

Check them twice a year, in spring and fall, and before a stretch of heavy rain. Milgard suggests inspecting weep holes when heavy rain is expected.
Keep paint and sealant off weep slots when painting or caulking around windows.
Lower indoor humidity in winter with bath and kitchen exhaust fans to reduce condensation between storm and main windows. Our Lars Knows: Condensation segment has more tips.
Look after the sills. Older wood windows need regular paint and caulk on the right surfaces. See our guide to wood window maintenance, and check your screens at the same time with our window screen repair guide.

Window weep holes: common questions

Do all windows have weep holes?

No. Many sliding, single-hung and storm windows do, especially vinyl and aluminum units. If you are not sure, look for slots on the outside of the bottom frame, or check your manufacturer’s care guide.

Should I caulk the weep holes to stop drafts?

No. Weep holes are designed to let water out, and many have flaps that limit air and insects. Caulking them traps water in the frame. If a window is drafty, look at its weatherstripping and the seal around the frame instead.

Why is there water between my storm window and my main window?

Usually it is condensation from warm, moist indoor air leaking past the main window, or rain getting behind the storm. Make sure the weep holes are clear, check that the main window closes and seals tightly, and lower indoor humidity. If water keeps collecting, have the windows checked.

Can a home inspector tell if a window has leaked?

We look for staining, soft wood, peeling paint and moisture damage around windows, and our moisture scanning can help find hidden moisture. Learn more about our home buyer inspections.

Window Weep Holes: Why They Clog and How to Clean Them