Window Wells: Covers, Drainage, Egress Compliance, and Waterproofing
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A window well is the excavation around a below-grade basement window that lets light in and provides emergency egress. When properly installed — with correct sizing, adequate drainage, and a cover — it works invisibly. When neglected, it becomes a funnel that channels water directly into the basement. Most window well problems are drainage problems.
Egress Code Requirements
Building code requires at least one egress window in every finished basement bedroom. The window must have a minimum net clear opening of 5.7 square feet, with a minimum width of 20 inches and a minimum height of 24 inches.
If the egress window is below grade, the window well must extend at least 36 inches from the window face and provide a minimum horizontal area of 9 square feet for wells deeper than 44 inches.
Wells deeper than 44 inches require a permanently attached ladder or steps. Egress well covers must be openable from the inside without tools.
Installation
Size the well to extend at least 6 inches beyond each side of the window frame and at least 8 inches deeper than the window sill.
Anchor the corrugated steel or composite well form to the foundation wall with concrete screws. Backfill behind the form, compacting in layers.
Fill the bottom with 6 to 12 inches of clean 3/4-inch gravel. This drainage layer is critical — do not skip it or substitute with topsoil.
Drainage
Every window well needs a drain. Install a PVC pipe from the bottom of the gravel bed to the perimeter footing drain, a dry well, or daylight on a downhill slope.
The pipe should slope at least 1/4 inch per foot toward the discharge point. Include a strainer cap at the well end to prevent gravel from entering the pipe.
In clay soil, a window well without a drain pipe will fill during any significant rain. Percolation drainage only works in well-draining soil.
Covers and Maintenance
Clear polycarbonate covers let light through while keeping water out. Mount at a slight angle so rain slides off.
Clean the well at least twice a year. Check that gravel is still 6 inches deep and the drain is not clogged.
Inspect the seal between the well and the foundation. If the well has pulled away from the wall, water flows behind it. Re-anchor and caulk the joint.
Frequently Asked Questions
My window well fills with water during rain. How do I fix it?
Check three things: Is the cover missing? Is the gravel bed full of sediment (replace with clean stone)? Is the drain pipe clogged or nonexistent? If all three are addressed and the well still fills, you need a drain pipe to a dry well or the footing drain system.
Do I need a window well if the window is only partially below grade?
If any part of the window is below the finish grade, a window well is recommended to prevent soil and water from contacting the window frame. It is required by code if the window serves as a bedroom egress point.