How to Fix a Leaky Window

How to Fix a Leaky Window

Updated: 02.15.2024

By Nina Tsoy

Is your home experiencing the inconvenience of air coming through window frames, or perhaps you’ve noticed water pooling around your window sill? Window leaks can be bothersome, leading to drafty rooms and potential water damage. When left unaddressed, these problems can result in higher energy bills and even mold growth.

But don’t worry, fixing a leaky window is often a straightforward and cost-effective task, especially with a team like ours on your side. In this guide, our pros at Apex Window Werks will explore the common causes of window leaks, how to spot them, and what to do about them.

Whether you’re considering DIY solutions or seeking the expertise of window repair services, our passionate team has got you covered. Don’t let window leaks disrupt your comfort – learn how to tackle this issue head-on and restore the integrity of your home’s windows.

Why Are My Windows Leaking?

Why Are My Windows Leaking?

Here are the common factors contributing to window leaks that are often characterized by water seepage or air infiltration around the window frame and sill.

Worn-Out Caulk and Seals

Over time, the caulk and seals used to create a water-tight barrier around windows can deteriorate. Cracks and shrinkage in the caulk can create gaps between the window and the frame, allowing water to penetrate. Damaged seals and locking mechanisms can result in moisture seeping through and lead to condensation between glass panes and potential leaks.

Clogged Drainage Holes

Did you know that windows feature small drainage holes designed to channel water away from the interior? When these holes become clogged with debris, water accumulation, and leakage may occur. Excessive dirt or blockage in the drainage channels can impact the proper flow of water, increasing the risk of window sill pooling.

Improper Window Flashing

Flashing serves as a protective barrier around the window frame to prevent water infiltration. If flashing is incorrectly installed or damaged, it can compromise its effectiveness and allow water to penetrate gaps or cracks around the window perimeter.

Defective Windows

Occasionally, window defects, such as manufacturing flaws or material defects, can result in leaks. These issues often become evident shortly after window installation and prompt the need for window replacement.

Improper Installation

Improper Installation

When installed correctly, windows should prevent leaks by ensuring there are no gaps or inadequately sealed areas. However, inadequate caulking or sealant application, along with improper window seating in the frame, can create opportunities for water intrusion.

Roof or Siding Leaks

Although not direct window leaks, problems with the roof or siding can manifest as water entering through windows. Water may infiltrate through damaged roofing materials or siding and cause it to drip or collect around the window frame or sill.

Design Flaws

Some window leaks result from design flaws in the structure of your home, such as insufficient overhangs or wall cracks. Identifying these design-related issues may require consultation with professionals to determine appropriate solutions.


It’s essential to consider alternative sources of moisture or air infiltration, such as missing shingles, wall cracks, or clogged gutters, which can mimic leaking windows. Thoroughly investigating potential problems can help avoid unnecessary window repairs or replacements.

Signs of a Leaky Window

Signs of a Leaky Window

You can determine whether your window is leaking if you experience the following indications:

  • Water coming in around windows: Obvious sign of a window leak with water seeping near the frame or into the panes, indicating a possible gap.
  • Rotten wood: Water damage to wooden frames causing rot or warping of trim, potentially requiring professional inspection.
  • Foggy windows: Trapped water between glass panes may signal a broken seal and lead to future issues.
  • Musty odor: Damp wood emits an unpleasant odor, often found in basements, possibly due to water ingress and potential mold growth.
  • Mold: Black mold spots on window frames indicate dampness and potential indoor air quality issues.
  • Discoloration: Water leaks cause frame discoloration, starting as a yellow stain and darkening over time.
  • Peeling paint: Moisture penetration can result in chipping paint or wallpaper as it weakens adhesion.
  • Floor damage: Water may reach the floor over time and result in issues like warped hardwood or moldy carpeting.
  • Damaged caulk: Missing or peeling window caulk can allow moisture and air infiltration.
  • Sagging drywall: Severe leaks can lead to sagging drywall, but prompt action can prevent structural damage.

      How to Find Where Cold Air Is Coming In

      Pinpointing the source of cold air infiltration is essential to address energy efficiency concerns and improve the comfort of your living space. To locate where air is coming into your home, we recommend that you follow the methods and steps below.

      Visual and Sensory Inspection

      Visual and Sensory Inspection

      Start by visually inspecting your windows for potential air leaks. Walk around the outside of your house and examine the junction where your siding meets the window frame. Look for any visible cracks or gaps in the building materials. Additionally, be on the lookout for signs of broken roof flashing that may contribute to leaks.

      During the daytime, go inside your home, turn off the lights, and inspect your windows for daylight seeping through gaps around the sides or at the bottom of the frame. On a cold day, hold your hand an inch away from the window frame and feel for any drafts.

      Flame Test with a Candle

      If you can’t detect air leaks through visual inspection or by feeling drafts, try a flame test with a candle. Light a candle and carefully trace the outline of your window with it. If the flame and smoke from the candle are pulled in a specific direction, this indicates the presence of an air leak. If it’s not immediately clear whether the smoke is moving, have someone stand outside the window with a hairdryer, tracing the window outline. If the candle’s flame flickers, it signifies that air is passing through the window.

      Thermal Camera Rental

      If you’re still struggling to locate air leaks, consider renting a thermal camera from your local hardware store. A thermal camera can provide a visual display of temperature differences, helping you identify areas of energy leakage around your windows. It can be useful not only for detecting air leaks but also for uncovering issues with insulation, ductwork, and roof insulation throughout your home.

      Ready to Leave Your Window Leaking Worries Behind?

      Contact our experts at Apex Window Werks for professional assistance!

      Schedule an Estimate

      or call us (847)-443-5145

      How to Repair a Window Leak

      While addressing small air leaks can be a cost-effective DIY project, it’s important to note that these repairs are often temporary, and full-frame window replacement may be necessary for long-term energy efficiency. Below, we’ll outline the tools you’ll need and two common methods for repairing leaky windows.

      Tools Needed

      To fix leaking windows, you’ll need:

      • Caulk and a caulking gun
      • Putty knife
      • Weatherstripping
      • Spatula
      • Paper towels

      Method 1: Sealing Air Leaks in the Window Frame and Grilles

      When it comes to fixing leaky windows, caulking is a practical and cost-effective solution. Follow this step-by-step guide to effectively seal those troublesome gaps and cracks, ensuring your windows are airtight and leak-free.

      Clean the Surface

      Begin by cleaning the areas around the leaking window that require caulking. Remove any old caulk or paint using a putty knife, ensuring the surface is dry and free of debris.

      Apply Caulk

      Use a caulking gun to apply caulk to the areas that need sealing. Apply the caulk at a forty-five-degree angle in a continuous stream so that it adheres to both sides of the seam.

      Address Excess Caulk

      If caulk leaks out of the crack during application, use the putty knife to push it back into place. If the caulk shrinks while drying, reapply a smooth line to seal the crack completely.

      Method 2: Sealing Air Leaks Between the Window Rail and Window Sill

      Let’s find out how to stop window leaks by properly measuring, cutting, and applying weatherstripping to create an effective seal.

      Clean the Area

      Start by cleaning the area you want to seal with soap and water. Make sure that it’s completely dry before proceeding.

      Measure and Cut Weatherstripping

      Measure the width of the window sill and cut the weatherstripping material to the appropriate size. Be sure to use weatherstripping that matches the width of the gap you’re sealing.

      Apply Weatherstripping

      Place the weatherstripping material onto both the window rail and the window sill surfaces. Make sure that the weatherstripping adheres securely. When you close the window, the material should compress and form an effective seal.

      Test for Leaks

      After completing the weatherstripping application, conduct tests to confirm that the air leaks have been effectively sealed. Perform the previously mentioned tests, such as the candle or smoke test, to verify that the leaks have been resolved.

      Average Costs for Repairing Leaky Windows

      Average Costs for Repairing Leaky Windows

      Our team knows that cost is at the forefront of your mind. The cost of repairing leaky windows by hiring professional services typically falls within the range of $170 to $620. Labor costs alone can vary from $30 to $50 per hour.

      While some may consider tackling more complex window repair projects themselves to save money, it’s important to remember that even minor errors could result in additional water damage or the need for window replacement, which can be significantly more expensive than hiring a professional from the outset.

      When to Seek Expert Assistance for Window Issues

      If you’re dealing with issues like a leaky window, it’s a wise move to get in touch with a trusted window repair and replacement company such as Apex Window Werks. With over 15 years in business, we proudly serve Illinois, Wisconsin, and Minnesota. With nearly 15,000 projects completed, see how we’ve earned a glowing reputation in the community.

      Our team of experts offers professional services to ensure your windows are in top-notch condition, including the correct installation of replacement windows, effectively resolving any problems you may face. Don’t hesitate to reach out and improve the comfort and energy efficiency of your home today.

      Nina Tsoy

      Nina Tsoy

      With over 15 years of experience in the window repair, replacement, and manufacturing business, Nina is in charge for strategic solutions and exceptional operational performance at Apex Window Werks. This allows her to offer innovative techniques and solutions to address any window-related problem, all while adhering to industry standards and best practices.

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