How to Install a Window Well Cover That Stops Leaks

TL;DR: Most window well leaks happen because the cover doesn't overlap the well by at least 2 inches on each side, or because the well itself has no gravel base and drain to move water away from the glass. Buy a cover rated for your well's width (measure at the widest point, not the frame), anchor it with the manufacturer's brackets, and pair it with 12 inches of gravel and a working drain at the bottom. Done right, this stops 90% of basement window leaks without touching the foundation.

_Last reviewed: July 2026 · 7 min read_

Water pooling in the window well outside your basement is one of those problems homeowners notice only after it's already inside the wall. The fix isn't complicated, but most covers sold at hardware stores are installed wrong, sized wrong, or missing the drainage step that actually keeps water out.

Okoniq Property Hub lets you log the well size, cover model, and install date for every basement window, so you're not guessing which one needs re-sealing next spring.

What size window well cover do you actually need?

Measure the well at its widest exterior point, not the window frame, and add at least 2 inches of overlap on every side. A well that's 36 inches wide and 24 inches deep needs a cover rated for at least 40x28, because covers that sit flush or short let rain run straight down the gap.

Covers come in three shapes: flat, bubble (low dome), and full dome. Flat covers are the cheapest, around $25 to $40, but they pool water on top and eventually sag or crack under snow load. A bubble or full dome cover, usually $50 to $90, sheds water to the sides instead of holding it, which matters more than the material in most climates. Polycarbonate domes handle hail and UV better than the thin plastic flat covers and typically last 8 to 10 years versus 3 to 5.

If your well is irregular, custom-cut steel mesh covers with a clear bubble insert run $100 to $150 but fit almost any shape without gaps.

How do you seal the edges so water can't get in?

The cover has to sit on brackets that hold it slightly above the well's rim, not resting directly on the foundation wall, because a flush seal traps humidity and invites mold. Most kits include galvanized steel or aluminum mounting brackets that screw into the foundation about 1 inch above the well's top edge, letting the dome sit at a slight angle so runoff drains to the sides instead of pooling in the middle.

Check the seam where the cover meets the house wall. This is the most common leak point because standard covers are cut straight across and don't hug an uneven stucco or brick surface. A bead of exterior-grade silicone caulk along that top edge, redone every 2 to 3 years, closes the gap without blocking airflow underneath. If your window is a legal egress window, don't caulk it shut. It has to open from inside without tools in an emergency, so leave the cover removable or hinged.

Does the well itself need drainage, or just the cover?

Both. A cover only stops rain from entering directly. It does nothing about groundwater or runoff that seeps in from the sides, which is the more common failure. Every window well should have 8 to 12 inches of ¾-inch gravel at the bottom sitting over a perforated drain pipe connected to your foundation drain or daylighted away from the house.

If your well has bare dirt at the bottom, that's the first thing to fix, before the cover. Dirt holds water against the window frame and the foundation wall, and freeze-thaw cycles push it against the glass over winter. Pull out any soil, add a few inches of gravel, and confirm there's a way for water to leave the well besides evaporation. This same runoff usually traces back to grading and gutters, which is worth checking alongside the well, similar to how downspout placement can dump water in the wrong spot and undo a good foundation seal.

What else causes window well leaks even with a cover installed?

Clogged perimeter drains and bad grading send water into the well faster than any cover can shed it. If your yard slopes toward the house instead of away from it, even a 6% grade reversal within the first 10 feet of the foundation can funnel gallons of runoff straight into the well during a heavy rain. Check this with a level and a 4-foot board before blaming the cover.

Downspouts discharging within 3 feet of a window well are another repeat offender. Downspout mistakes that send water into the basement often start exactly here, where a short downspout extension dumps roof runoff directly into the well it's supposed to protect. Extend downspouts at least 5 feet from the foundation and redirect them away from any window well.

If leaks persist after a properly sized cover, gravel base, and corrected grading, the water may be coming from below rather than above. That points toward a foundation crack or a slab leak rather than the window well itself, and it's worth ruling that out before replacing hardware that's already working correctly.

FAQ

How much does a window well cover installation cost?

A DIY install with a bubble-style polycarbonate cover, brackets, and gravel runs $80 to $150 per window. Hiring a handyman adds $50 to $100 per well in labor, and custom-fit steel mesh covers for irregular wells can push the total to $200 to $250.

Can I install a window well cover myself?

Yes, most kits install in under an hour per window with a drill, exterior screws, and a caulk gun. The gravel and drain work underneath takes longer, usually 1 to 2 hours per well if the well needs to be dug out first.

Do window well covers block emergency egress?

Not if installed correctly. Egress-rated covers use hinges or a quick-release latch so the window can still open fully from inside without tools, which is required by most local building codes for bedroom-level basement windows.

How often should I replace a window well cover?

Plastic flat covers typically need replacement every 3 to 5 years due to UV cracking and sagging. Polycarbonate dome covers and steel-frame mesh covers usually last 8 to 12 years before the plastic yellows or brackets rust through.

Will a cover alone stop all basement window leaks?

No. A cover stops direct rainfall but not groundwater seepage or poor grading runoff. Pair it with a gravel base, working drain, and downspouts extended at least 5 feet from the foundation for it to actually work.

This is educational information, not construction or waterproofing advice. Call a licensed foundation contractor if you see persistent water intrusion, cracking, or settling near a window well.