How to Cover a Window Well | Fit, Fasten, and Keep Water Out

An uncovered window well collects leaves, snow, and rain runoff that can push moisture against your basement walls. A proper cover keeps that debris out while letting daylight through, and the installation is a straightforward afternoon project whether you buy a pre-made unit or build one yourself.

What Kind of Cover Should You Use?

Clear rigid plastic is the most common choice when you want natural light in the basement, and polycarbonate is frequently marketed as UV-resistant for window well applications, which makes it a strong option for sunny exposures. Metal grates are the better pick when you want more open airflow and don’t mind losing some light.

Lowe’s maintains a full window well cover buying guide, and the product category is standard stock at Lowe’s, Home Depot, and Ace, so you have plenty of commercially made options. If you’re shopping for a durable ready-made cover, our tested roundup of the best durable window well covers compares the top-rated models side by side.

How to Install a Store-Bought Cover

Retail installation guides agree on the core principle: the cover should sit so the window well edges support nearly all of its weight, with the back edge snug against the house. Lowe’s says to center the cover over the well and verify there is no buckling or clip bending after fitment.

Here’s the step order that works for most pre-made covers:

• Measure and mark mounting locations. On non-egress windows, mark the sides and the front; on egress windows, omit the front clip entirely.
• Drill pilot holes slightly larger than the supplied screws so the plastic doesn’t crack.
• Fasten the clips to the well rim, then test-fit the cover and confirm it doesn’t buckle.

The Home Depot Bubble Window Well Cover instructions follow a similar pattern: place the cover over the well, drill mounting holes through the plastic flanges on both sides, mark anchor locations, remove the cover, drill the anchor holes to size, then reposition and secure with anchors. Their instructions add two important notes: fill any remaining gaps with caulk, but maintain sufficient ventilation so moisture can escape.

Building a DIY Cover That Lasts

If you’d rather build your own, Family Handyman describes a sloped frame made from pressure-treated 2×8 triangles with 2×4 bracing, topped with plywood or plexiglass and attached with hinges. A lighter variant uses 1-1/2-inch PVC pipe and fittings with clear corrugated roofing fastened by self-drilling roofing screws.

For a simple flat cover, trace the well opening onto acrylic or polycarbonate and add about 1 inch of overhang, then hold it in place with spring clips. For oversized wells, build a framed cover with hinges and add extra brackets or weights so wind and animals can’t shift it.

Whatever material you choose, smooth any rough-cut acrylic edges or add edge trim — sharp edges are a cut hazard and a place for cracks to start.

Common Mistakes That Ruin a Window Well Cover

Three errors cause most failures, and all of them are easy to avoid once you know they exist:

• Measuring only the window opening. The well lip extends beyond the window, and a cover that ignores it will sit awkwardly with gaps. Measure the full well rim.
• Securing an egress window cover too rigidly. For basement egress windows, the whole point is getting out in an emergency. Lowe’s says to install only one clip on each side and none in the front so the cover can be nudged out of the way when the window opens.
• Over-tightening the clips or screws. Overtightening deforms the cover plastic or bends the hardware. Snug is enough — one installation guide explicitly warns against over-tightening.

Two more issues quietly cause long-term problems. A flat cover with no slope traps water instead of shedding it, so build in some pitch or rely on drainage gaps. And if the cover might ever support weight — a child climbing on it, or snow piling up — a thin DIY plastic sheet isn’t rated for that. Choose a product the manufacturer specifically rates for load and follow its instructions.

When you’re ready to buy rather than build, check our durable window well cover picks for models that handle snow and weight well.