Basement Window Well Drain Installation and Waterproofing
Window well drain installation costs $200 to $800 per window well, with most homeowners spending $300 to $500 per well for a complete drain and gravel system. Adding a window well cover costs $50 to $200 per window. Window wells are a common entry point for basement water because they collect rain, snow melt, and surface runoff in a concentrated area directly against the foundation wall, often at or below the level of the basement floor.
Why Window Wells Flood Basements
Basement window wells are corrugated metal or plastic enclosures set into the soil around below-grade windows. They hold back the surrounding earth and provide light and ventilation to the basement. The problem is that they also collect water. Rain falls directly into an open window well, roof runoff from above can cascade into the well, and surface water from poor grading flows toward the low point the well creates against the foundation.
When water fills a window well faster than it can drain, it rises to the window level and enters the basement through the window frame, the window seal, or through the foundation wall around the window opening. A single heavy rainstorm can fill an unprotected window well in minutes, sending gallons of water into the basement before the homeowner realizes what is happening.
This is one of the most preventable sources of basement flooding, yet it is frequently overlooked during waterproofing projects that focus only on the wall-floor joint and perimeter drainage. A complete waterproofing strategy should include window well drainage as part of the overall system.
Step 1: Clear the Window Well
Remove all debris, leaves, soil, and old gravel from the window well down to the foundation wall base. Over time, organic debris accumulates in window wells and compacts into a layer that blocks drainage. If the well has an existing drain, it may be clogged with this debris. Clear everything to expose the bottom of the well and the base of the foundation wall.
Step 2: Dig the Drain Pit
Excavate a hole 12 to 18 inches deep and approximately 12 inches in diameter at the lowest point of the window well, typically in the center at the base of the foundation wall. This pit provides a collection point for water and a connection point for the drain. If the window well is large, dig the pit at the low corner where water naturally collects.
Step 3: Install the Drain Pipe
The best option is to connect the window well drain to your interior perimeter drainage system by coring a hole through the foundation wall at the base and running a pipe from the window well pit through the wall to the interior french drain. This costs $200 to $500 per window if done during a perimeter drain installation, or $400 to $800 as a standalone project. The alternative is a vertical drain pit filled with gravel that allows water to percolate into the soil below the well, but this only works in well-draining soils and is less reliable than a connected drain.
Step 4: Fill With Clean Gravel
Fill the window well with 6 to 12 inches of clean, washed gravel (3/4 inch or pea gravel). The gravel serves two purposes: it allows water to flow freely to the drain at the bottom rather than pooling on a flat surface, and it prevents soil from washing into the well and clogging the drain. Do not use dirt, mulch, or decorative stone that can compact and block drainage.
Step 5: Install a Window Well Cover
A clear polycarbonate window well cover is the most effective preventive measure you can add. The cover fits over the top of the window well enclosure and prevents rain, snow, leaves, and debris from entering the well. Clear covers allow natural light to pass through to the basement window. Covers cost $50 to $200 depending on the size and shape of the well, with custom-fit covers at the higher end. Bubble-style covers that rise above the well opening provide more headroom and allow the window to open for ventilation.
When to Hire a Professional
Window well drain installation is one of the few waterproofing tasks that a handy homeowner can complete as a DIY project, at least for the gravel fill and cover installation. However, coring through the foundation wall to connect the drain to the interior system requires specialized equipment (a core drill) and knowledge of the foundation structure. This portion should be done by a waterproofing contractor, ideally during the perimeter drain installation when the interior system is already being worked on.
If your window wells are flooding and you already have an interior perimeter drain, adding window well connections to the existing system is a straightforward upgrade that most waterproofing companies can complete in a few hours per window. If you do not yet have an interior drainage system, the window well drains can be installed as part of the overall waterproofing project at minimal additional cost. See our french drain cost guide for full system pricing.
Window Well Maintenance
Even with proper drains and covers, window wells need periodic maintenance. Check the gravel level annually and add more if it has settled. Clean debris from the cover surface and from inside the well in spring and fall. Test the drain by pouring a bucket of water into the well and verifying it drains within a few minutes. If water pools and does not drain, the drain pipe may be clogged and needs clearing.
Inspect the window well enclosure for rust, damage, or separation from the foundation wall. A gap between the enclosure and the wall allows soil and water to bypass the well and enter directly against the foundation. Seal any gaps with exterior caulk or replace the enclosure if it is damaged. Make sure the grade around the top of the window well slopes away from the well opening so surface water does not flow into it.
Window well drains at $200 to $800 per well, combined with covers at $50 to $200, are an inexpensive addition to any waterproofing project that eliminates a common and preventable source of basement flooding.