Window Well Drainage
Window well drainage, the Denver way.
The well isn't the problem. The drainage detail underneath it is. Here's how Denver wells should be built so they don't flood your basement.
A flooded window well is one of the most common basement service calls in Denver, and almost every case traces back to the same failure: the original installer set the well on dirt or shallow gravel and never tied it to a drainage path. When snow melts, when a thunderstorm dumps an inch in twenty minutes, when our clay soil saturates and stops absorbing — the water has nowhere to go but into your basement.
The right detail
- Excavate the well opening to at least 12–18 inches below the finished well bottom.
- Install a layer of clean drain rock wrapped in non-woven filter fabric.
- Tie that gravel base to either the foundation perimeter drain (preferred) or to a horizontal outfall daylighted into the yard at lower grade.
- Anchor the well mechanically into the foundation — not just into the surrounding soil.
- Backfill with free-draining material, slope grade away from the well, and add a clear polycarbonate cover.
Skipping any one of these steps is what causes the leak you're trying to avoid. We do all five on every window well install and every egress window project.
How Denver freeze-thaw drives well failure
Denver's freeze-thaw cycle runs from October through April and is the single most aggressive force acting on a basement window well. Every day the temperature crosses 32°F, water trapped in the gravel base, the soil around the well, and the joint between the well and the foundation expands roughly 9% as it freezes — then contracts as it thaws. Over a few seasons, that movement pumps gravel down into the surrounding clay, opens the seal between the well and the foundation, and lets snow-melt water find the inside of your basement.
The defense is the same on every install: oversize the gravel base so the freeze front never reaches the bottom, wrap the rock in non-woven fabric so fines can't migrate in, and mechanically anchor the well to the foundation so seasonal soil movement can't pry it loose. See the window well system page for the full build, or read how this fits into a complete egress window installation.
Call or text us — and turn your dark basement into a bright, legal bedroom.
Pick up the phone or text photos of your basement wall and exterior — we'll tell you exactly what it takes to make the room code-compliant, daylit, and safe. No forms, no pressure, no sales pitch.
Or schedule a basement assessment