Why Basement Windows Leak After Heavy Rain (And When The Foundation Is The Real Problem)

A leaking basement window does not always mean the window has failed. 

The water may be entering through the frame or seal, but it can also come from a flooded window well, poor grading, a blocked drain, or a crack in the surrounding foundation. 

This is why replacing the window does not always solve the problem.

TL;DR

• Water around the frame: Check the seal, frame, and installation.
• Standing water in the window well: The drain may be blocked or damaged.
• Water flowing over the top of the well: The well may be too low or the ground may slope toward the house.
• Water beside or below the window: A foundation crack may be the real source.
• Water rising through the gravel: The problem may involve groundwater or foundation drainage.
• Leak continues after the rain stops: Saturated soil may be pressing water against the foundation.

A window contractor handles the window itself. A waterproofing contractor handles the well, grading, drainage, cracks, and foundation.

Start With The Obvious Question: Is The Window Actually Leaking?

The best place to start is with the window assembly.

Look for:

• Cracked or missing exterior sealant
• A damaged or warped frame
• Water entering through the sash
• Gaps between the frame and concrete
• A window that does not close properly
• A leak that started soon after installation

If water is clearly entering through the frame or around the perimeter, the window may need repair or replacement. 

The Window Experts can inspect the glass, frame, seal, and installation to determine whether the window itself is the problem.

Also Read: Water Dripping From Top Of Window Frame

A New Basement Window Can Still Leak

A properly installed basement window can still leak if the window well fills with water. 

Basement windows sit much closer to the ground than upper-floor windows. In many homes, they are surrounded by soil, gravel, and a metal or concrete well.

During heavy rain, water may collect around the opening. If the well fills high enough, water can press against the window and enter through small gaps. 

This does not automatically mean the window was installed incorrectly.

It may mean the drainage system around it is not working.

Clogged Window-Well Drain

A window well should not hold standing water. Many wells have a drain below the gravel. Leaves, soil, roots, sediment, and debris can block that drain.

Common signs include:

• Water sitting in the well after rain
• Mud covering the gravel
• Water rising quickly during a storm
• Water marks on the glass
• Leaks that only happen during heavy rainfall

Removing surface debris may help, but it will not fix a broken, disconnected, or collapsed drain. 

If the water keeps returning, the drainage below the well needs to be checked.

Window Well Installed Too Low

The top of the well should sit above the surrounding soil. If the soil, mulch, driveway, or walkway is higher than the well, surface water can flow directly into it.

This often happens after:

• New landscaping
• Added topsoil or mulch
• Driveway resurfacing
• Soil settlement
• Changes to a walkway or patio
• Poor original installation

A window-well cover can reduce rain and debris, but it will not fix a well that sits too low.

Also Read: Enbridge Window Rebate In Ontario

Poor Grading Around the House

The ground around the foundation should slope away from the house. 

When it slopes inward, rainwater collects beside the basement wall and window well. This can overload the well drain and increase water pressure against the foundation.

Look for:

• Puddles beside the house
• Soft or muddy soil
• Downspouts emptying near the window
• Garden beds sloping toward the wall
• A driveway or walkway directing water inward

Correcting the grade may reduce the problem, but it will not repair a crack or failed waterproofing system.

Foundation Cracks Near the Window

Foundation cracks often form near basement window openings. 

The crack may start at one corner of the window and continue through the concrete. Water can enter through that crack and appear beside or below the frame.

This can make it look like the window is leaking even when the window itself is in good condition.

Signs of a foundation problem include:

• A visible crack near the window
• Damp concrete beside the frame
• Water staining below the opening
• White powdery deposits
• Peeling paint
• A musty smell
• Water entering when the well is not full

In these cases, resealing or replacing the window will not stop the leak. The surrounding foundation needs to be repaired.

Also Read: Egress Windows For Basements

Water Rising From Below

Water rising through the gravel in a window well usually points to a larger drainage problem.

Possible causes include:

• A blocked window-well drain
• A failed connection to the foundation drainage system
• Saturated soil
• High groundwater
• Failed weeping tile
• Hydrostatic pressure

This type of problem is different from rain entering from above. A cover over the well will not stop water rising from below.

When The Foundation Is The Real Problem

You likely need a waterproofing inspection when:

• The well fills with water
• Water rises through the gravel
• A foundation crack is visible
• The ground slopes toward the house
• Water appears below the window
• Several basement areas become wet
• The leak continues after the window is repaired
• The problem gets worse during spring thaw

For foundation, drainage, grading, or window-well problems, homeowners can contact Canada Waterproofers for basement waterproofing and drainage assessment.

When The Window Is The Real Problem

A window contractor is the right call when:

• The frame is cracked or warped
• The window does not close properly
• Water enters through the sash
• The perimeter seal has failed
• The glass unit is fogged
• The installation is poor
• The window is old or deteriorated
• A larger egress opening is needed

The Window Experts can inspect the window itself and determine whether repair or replacement is necessary.

The Right Repair Depends On The Source

Replacing the wrong component wastes money. 

A new window will not fix a blocked drain. New caulking will not stop water entering through a foundation crack. A window-well cover will not solve groundwater pressure.

The correct repair starts with finding out whether the problem is:

• The window
• The window well
• The drainage
• The grading
• The foundation

Frequently Asked Questions

Why does my basement window only leak during heavy rain?

Heavy rain may overwhelm a partly blocked drain, fill a low window well, or saturate the soil around the foundation. Small problems often become visible only during major storms.

Can a new basement window still leak?

Yes. A new window can leak if the well fills with water, the surrounding grade is poor, or the foundation has a crack.

Will a window-well cover stop the leak?

It may reduce rain, snow, and debris entering from above. It will not fix poor grading, groundwater, a damaged drain, or foundation cracks.

Is standing water in a window well normal?

No. Water should drain away. Standing water usually means the drain is blocked, damaged, missing, or overwhelmed.

Who should inspect the problem?

A window contractor should inspect the frame, glass, seals, and installation. A waterproofing contractor should inspect the foundation, window well, grading, cracks, and drainage.

Need The Window Checked?

The Window Experts provides basement and egress window inspections and installation services across Toronto and the Greater Toronto Area. 

We inspect the window, frame, seal, and opening to determine whether the problem is with the window itself or the surrounding foundation and drainage.