Why does water collect in my basement window well?

Window well flooding has three main causes: (1) Missing or clogged drainage at the bottom of the well — the gravel drainage bed has become compacted or filled with soil and debris, preventing water from draining into the soil below. (2) The well liner is pulling away from the foundation wall, creating a gap where surface water flows directly against the foundation. (3) Surface grading directs water toward the window well rather than away from it — negative grading (soil sloping toward the house) funnels rainwater and snowmelt directly into the well.

How deep should the gravel be in a window well?

The gravel drainage bed at the bottom of a window well should be at least 12 inches deep — ideally 18 inches. Coarse washed gravel or crushed stone (3/4-inch or larger) is most effective. Fine pea gravel clogs more quickly with sediment. The gravel provides temporary storage during heavy rain and allows water to percolate into the soil below the well. Over time, sediment fills the void space in the gravel and drainage slows — remove and replace the gravel every 5 to 10 years.

Do I need a window well cover?

A window well cover is one of the most effective ways to prevent flooding. A properly fitting polycarbonate or aluminum dome cover sheds rain directly off the well, preventing rain from entering at all. It also keeps out leaves, debris, and animals. For egress windows (escape windows required by code in bedrooms), use an egress-compliant cover that can be opened from inside without tools. Covers reduce well flooding by 80 to 90 percent and also reduce heat loss through basement windows in winter.

Can I seal the window well liner to the foundation myself?

Yes. Where the window well liner meets the foundation wall, apply hydraulic cement or polyurethane foundation sealant into any gap. Clean the joint thoroughly, remove loose material, and press the sealant into the gap. On the exterior surface of the well liner where it meets the foundation, apply a bead of polyurethane or butyl caulk. These repairs are DIY-accessible and typically cost under $30 in materials.

My basement window leaks even when the well is dry. What is causing that?

If the window well itself is dry but the window leaks, the problem is the window — not the well. Common window leak sources: failed caulk around the window frame on the exterior, cracked or missing glazing compound around the glass, a deteriorated window gasket, or a wood window frame that has rotted and no longer seals against the opening. Inspect the window frame and caulk thoroughly from outside and from inside the basement. Re-caulk the exterior perimeter of the window frame with polyurethane or silicone caulk.

When should I install a window well drain connected to an interior drain tile system?

A drain connected to the interior drainage system is the right solution when the soil drainage around the foundation is fundamentally poor — clay-heavy soil that does not drain regardless of how deep your gravel bed is, or a high water table that brings groundwater up faster than it can drain. In these situations, surface fixes (deeper gravel, better grading) temporarily slow the flooding but do not solve it. A drain pipe at the bottom of the well connecting to an interior perimeter drain or sump pit is a permanent solution. This is a larger project that typically involves a waterproofing contractor.

How to Fix a Leaking Basement Window Well: Step-by-Step Guide

A flooded window well is a direct path for water to enter your basement.

A flooded window well is a direct path for water to enter your basement. Most well flooding can be fixed with better drainage, a sealed liner, and a cover — all DIY-accessible repairs.

What You Need

Coarse gravel or crushed stone (3/4-inch washed gravel, one to two 50-lb bags)
Window well cover polycarbonate dome — measure your well opening before ordering
Hydraulic cement or polyurethane foundation sealant
Polyurethane caulk (for liner-to-foundation gap)
Caulk gun
Trowel or margin trowel
Garden trowel or spade
Wire brush
Garden hose

Step 1: Clean Out the Window Well Completely

Remove everything from the well — all debris, old gravel, leaves, and standing water. This gives you a clear view of the well floor and liner condition.

With the well empty, probe the floor with a screwdriver or stick. The floor should be coarse gravel 12 to 18 inches deep. If the material is compacted, muddy, or appears to be mostly soil, the drainage bed has failed and needs to be replaced.

Look at the well liner (the metal or plastic curved wall):

Is it tight against the foundation on both sides?
Does it sit flush against the foundation face, or is there a visible gap?
Are there holes or cracks in the liner body?

Look at the foundation wall behind the liner:

Efflorescence (white mineral deposits): indicates water has been seeping through the foundation wall
Active cracks: visible hairline or larger cracks in the foundation block or poured concrete

Step 2: Seal the Liner-to-Foundation Gap

The most common water entry point in a window well is the gap between the liner and the foundation wall where the liner is supposed to seal against the foundation.

Press the liner firmly against the foundation. If it has pulled away, you may need to temporarily brace it in position while the sealant cures.
Clean the gap thoroughly with a wire brush and remove all loose material, dirt, and old caulk.
For gaps larger than 1/2 inch: fill with hydraulic cement. Mix to a thick paste, press it firmly into the gap with a margin trowel, and smooth flush. Hydraulic cement cures in 3 to 5 minutes and stops active water seepage.
For smaller gaps and surface sealing: apply a continuous bead of polyurethane caulk along the full perimeter where the liner meets the foundation wall. Tool it into the joint and smooth flat.

Also check and seal where the liner end-tabs anchor into the foundation or into the soil beside the foundation. These anchor points are secondary water entry locations if they are loose.

Step 3: Refresh the Gravel Drainage Bed

With the old drainage material removed and the liner resealed, add fresh coarse gravel:

Shovel 12 to 18 inches of clean coarse gravel (3/4-inch crushed stone or washed gravel) into the bottom of the well. Do not use fine pea gravel or sand — fine particles clog quickly and reduce drainage.
Level the gravel surface with a trowel.
Test drainage by running a garden hose into the well for 2 to 3 minutes at full flow. The water level should rise slowly and then begin to drop as it percolates through the gravel into the soil below. If water rises and stays without dropping, the soil below has poor drainage — consider adding a drain pipe (see FAQ above).

Step 4: Improve Surface Grading Around the Well

Even a well-drained window well will flood if surface water is directed toward it. Walk around the perimeter of the window well and look at how the soil is graded:

Negative grade (soil slopes toward the well): Add topsoil to build the grade up and away from the foundation. The finished grade should slope away from the house at a minimum of 6 inches over the first 10 feet. For the area immediately around the window well, slope the soil so water drains away from the well opening on all sides.
Downspout discharge near the well: If a gutter downspout discharges near the window well, extend it with a flexible downspout extension to carry water at least 6 feet away from the foundation. A single heavy rain can dump hundreds of gallons of water near a foundation from one downspout — keeping that discharge well away from the window well makes a dramatic difference.

Step 5: Install a Window Well Cover

A cover is the single most effective way to prevent window well flooding. It keeps rain out entirely, which means the drainage system only has to handle groundwater seepage rather than direct rainfall.

Measure the window well opening:

Width at the widest point (front, at the foundation)
Depth from the foundation wall to the front of the well liner

Most window well covers come in standard sizes (32, 36, 40, 48, and 60 inches wide). Buy the next size up from your measurement if your well falls between sizes — a slightly oversized cover that overhangs the edges is more effective than a cover that exactly matches the opening.

Install the cover:

Set the cover over the well opening with the high point of the dome toward the back (foundation side) so rain runs off to the front.
Most covers anchor with concrete screws driven into the foundation wall at the back of the well, or with lag screws into the wood framing beside the window opening. Follow the manufacturer’s instructions for your specific cover model.
If the cover fits loosely, use foam weatherstripping or caulk around the edge to prevent wind-driven rain from entering under the cover edge.

Step 6: Seal the Window Frame

If water still enters the basement after addressing the well drainage and cover, inspect the basement window itself. Re-caulk the full perimeter of the window frame on the exterior with silicone or polyurethane caulk. Pay particular attention to the joint between the window frame and the foundation opening — this joint commonly opens up as the framing dries and shrinks over years.

⏰ PT2H 💰 $10–$50 🔧 Pry bar, Shims, Level, Exterior caulk, Expanding foam insulation

Clean Out the Window Well Completely
Remove everything from the well — all debris, old gravel, leaves, and standing water. This gives you a clear view of the well floor and liner condition.
Seal the Liner-to-Foundation Gap
The most common water entry point in a window well is the gap between the liner and the foundation wall where the liner is supposed to seal against the foundation.
Refresh the Gravel Drainage Bed
With the old drainage material removed and the liner resealed, add fresh coarse gravel:
Improve Surface Grading Around the Well
Even a well-drained window well will flood if surface water is directed toward it. Walk around the perimeter of the window well and look at how the soil is graded:
Install a Window Well Cover
A cover is the single most effective way to prevent window well flooding. It keeps rain out entirely, which means the drainage system only has to handle groundwater seepage rather than direct rainfall.
Seal the Window Frame
If water still enters the basement after addressing the well drainage and cover, inspect the basement window itself. Re-caulk the full perimeter of the window frame on the exterior with silicone or polyurethane caulk.

How to Fix a Leaking Basement Window Well: Step-by-Step Guide

What You Need

Step 1: Clean Out the Window Well Completely

Step 2: Seal the Liner-to-Foundation Gap

Step 3: Refresh the Gravel Drainage Bed

Step 4: Improve Surface Grading Around the Well

Step 5: Install a Window Well Cover

Step 6: Seal the Window Frame

Free: 10-Point Home Maintenance Checklist

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How to Fix a Leaking Basement Window Well: Step-by-Step Guide

What You Need

Step 1: Clean Out the Window Well Completely

Step 2: Seal the Liner-to-Foundation Gap

Step 3: Refresh the Gravel Drainage Bed

Step 4: Improve Surface Grading Around the Well

Step 5: Install a Window Well Cover

Step 6: Seal the Window Frame

Related Guides

Free: 10-Point Home Maintenance Checklist

Save this for next time.