5 Common Causes of Window Leaks 

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1. Installation Issues

Poor installation is the most common cause of window leaks. Even the best window won’t perform properly if it's installed incorrectly. Here's why installation problems lead to leaks:

• Incorrect or missing flashing
  Flashing is designed to direct water away from the window and wall. If it's poorly installed, water can flow straight into the building envelope.

• Improper sealing or use of low-grade sealants
  Gaps left between the frame and the wall due to rushed or uneven sealing allow water and air to get through.

• Wrong window size or misalignment
  A window that doesn’t fit snugly in the opening can leave gaps where water finds its way inside.

• Lack of professional expertise
  Unqualified installers may skip critical steps or lack the knowledge to seal and secure the window correctly.

🔧 Tip: Always engage experienced professionals to install your windows to avoid costly water damage and ensure long-term performance.

 

2. Cracked or Deteriorated Caulking

Caulking around the exterior perimeter of windows acts as a protective barrier against water. Over time, caulk naturally deteriorates—especially under harsh sun, rain, or temperature fluctuations.

• Cracked, shrinking, or peeling caulk allows water to seep between the window frame and the building.

• Ageing homes often show this wear, even if the windows themselves are intact.

🔧 Tip: Inspect the caulking around your windows at least once a year and reapply high-quality exterior-grade caulk if you see any gaps or cracks.

 

3. Failed Window Seals

In multi-pane (double- or triple-glazed) windows, the seal between the glass panes plays a critical role in keeping moisture and air out.

• Broken seals can cause condensation or fog between the panes—and worse, let water leak into the frame or wall.

• Old windows are especially vulnerable as their seals deteriorate over time due to UV exposure and material fatigue.

🔧 Tip: If you see condensation between the glass panes, the seal is likely compromised. Replacing the window pane or sash may be necessary to stop leaks and restore energy efficiency.

4. Inadequate Drainage

Water needs somewhere to go. If your window’s drainage system isn’t working properly, water can pool in the frame or sill and eventually leak inside.

• Clogged weep holes or blocked tracks prevent water from draining away during rain.

• Flat or improperly sloped sills can cause water to collect and seep through.

🔧 Tip: Keep your window sills, tracks, and weep holes clean and free of debris. Water should always flow away from your home—not into it.

5. Structural Issues Around the Window

Sometimes, the window itself isn't the problem. Structural issues in the surrounding walls, cladding, or roof can channel water toward the window opening.

• Damaged cladding, brickwork, or roofing can let water travel along paths that lead straight to the window.

• Compromised wall framing or insulation can allow leaks to appear at the window, even if the issue started elsewhere.

🔧 Tip: If leaks continue even after replacing seals or flashing, a full building inspection may be needed to locate hidden structural problems.

Worried About a Leak? Let’s Fix It.