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Last updated on July 2nd, 2024 at 11:45 am

Windows can leak for various reasons, including poor installation, damaged sealant, cracked glass, missing or damaged weather stripping, and water damage from sources like clogged gutters or damaged roofing. Identifying the specific cause of the leak is essential for effective repair and maintenance.

40% of all windows tested showed air-leakage characteristics higher than the 0.50 cfm/lfc standard. This guide will explain common reasons why your windows might be leaking, as well as what you can do to fix each issue. If you are looking for window installation, get in touch with Warmable today who can find you a fitter in your local area. 


Poor Installation

Windows that are not properly installed can lead to leaks due to gaps and misalignment. When windows are not level, square, or plumb, they may not seal properly, creating opportunities for water infiltration.

Consult a professional window installer or contractor to assess the issue and potentially reinstall the window. Proper installation includes precise measurements, correct leveling, and the use of appropriate sealing materials.

One way to avoid poor installation issues is to make sure your windows are fitted by a trusted registered professional. Warmable can connect you with a trusted professional for free. All you need to do is fill in our quick form and we can connect you to a local engineer from our wide network.


Damaged or Worn Window Sealant

Over time, the sealant used around windows can deteriorate or become damaged due to exposure to the elements, UV radiation, and temperature fluctuations. Cracks or gaps in the sealant compromise its ability to prevent water from entering your home.

To solve this, carefully remove the old, damaged sealant. Clean the area thoroughly before applying new sealant. Finally, select a high-quality, waterproof sealant to ensure a long-lasting and effective seal.


Faulty Weather Stripping

Weather stripping plays a critical role in creating a barrier against moisture, drafts, and insects. Damaged, missing, or deteriorated weather stripping can lead to leaks.

To fix this, inspect the weather stripping around your window frame and replace any that is damaged or worn.Choose weather stripping materials that are suitable for your climate and provide a secure seal.


Cracked or Broken Window Panes

Cracked or broken window panes can create direct paths for water to enter your home. This problem is especially common in older windows or those subjected to harsh weather conditions.

When dealing with cracked or broken panes, it is essential to replace them.Consult a professional glazier to ensure the correct installation of new window panes. You can use services like Warmale to connect you to a trusted local professional.



Condensation occurs when warm, moist indoor air meets a cold window surface, leading to moisture buildup on the window surface and sills. Over time, this can result in water damage and leaks. You can read more about how to keep your home warm this winter here.

To address condensation, improve ventilation in your home by using exhaust fans and opening windows. Reduce indoor humidity levels with the use of a dehumidifier. Consider upgrading to double or triple-pane windows, which provide better insulation against temperature differentials.


Improper Drainage

Inadequate drainage systems can cause water to accumulate around your windows. Poorly designed or clogged drainage channels and weep holes can lead to leaks.

Ensure that your windows have appropriate drainage systems in place, including weep holes and channels. Regularly clean and maintain these drainage features to prevent clogs and blockages.


Damaged or Clogged Gutters

Clogged or damaged gutters can lead to rainwater overflowing, running down the walls, and collecting around your windows. This overflow can result in water infiltration.

Fix this with regular gutter cleaning and maintenance, removing leaves, debris and any obstructions. Repair any damaged gutter sections to ensure water is channeled away from your windows and foundation.


Roofing Issues

Roofing problems, such as missing or damaged shingles, can result in water seeping down the walls and into your windows. If the roof is compromised, water can easily find its way to the interior.

To address these issues, regularly inspect and maintain your roof to ensure the integrity of the shingles and flashing. Repair or replace damaged roof components to prevent water from entering your home through the ceiling or walls.


Settlement or Foundation Problems

Foundation settlement or structural issues can sometimes cause windows to become misaligned, leading to leaks. As the foundation settles, it may shift the window frame out of its original position.

Consult a structural engineer to assess and address any foundation or settling issues.Repairing these underlying problems can help realign your windows and prevent further leaks.


Storm Damage

Severe weather, including heavy rain, strong winds, and hail, can damage windows and cause leaks. Wind-blown debris can break window panes, and heavy rainfall can overwhelm window seals.

After severe weather, inspect your windows for damage. Replace any broken panes, repair or replace damaged seals, and ensure that the windows are properly sealed to prevent leaks.


Old Windows

Over time, windows can lose their effectiveness at keeping out the elements due to material deterioration and weakening seals. Older windows may develop gaps or become less energy-efficient, leading to water infiltration.

If your windows are old and showing signs of wear, consider replacing them with modern, energy-efficient models such as double glazed or uPVC. New windows typically feature improved materials and technologies that provide better insulation and weather resistance. Find the best uPVC window manufacturers through Warmable. 


Pest Infestation

Insects and rodents can sometimes create leaks by damaging window seals or nesting in window frames.Pests can chew through sealant or create openings that allow water to enter.

Inspect your windows for signs of pest infestation and address the issue promptly. Repair any damage caused by pests and take measures to prevent future infestations, such as sealing entry points.


Inadequate Flashing

Window flashing is a crucial element of proper window installation. It acts as a water repellent border around the window frame. If there are breaks or gaps in the flashing, water can seep into the wall, leading to leaks.

To address this issue, ensure that window flashing is correctly installed during the window replacement or installation process.Regularly inspect window flashing for any damage or deterioration and repair or replace it as needed.


Unlevel Windows

Windows that are not correctly leveled can lead to water pooling and leaks. Use a spirit level to check the alignment of your windows. If they are not level, water may accumulate along the base, causing leaks.

To rectify uneven windows, consult a professional installer to realign the window frame and ensure proper leveling during installation. If you get new windows installed, we have compiled a list of the best double glazing companies to consider in 2023.


Poor Sealing

Proper sealing is essential for preventing window leaks. Windows are typically sealed with expanding foam, but if too little foam is used, it can create gaps between the window and the wall, allowing water to enter.

Ensure that your installer accurately measures the window aperture and installs windows that fit precisely without the need for excessive foam. If you suspect poor sealing, consult a professional to address the issue and improve the sealing around the window.


Missing or Broken Caulking

The exterior seams of windows are sealed with caulk (sealant) to act as a barrier against water. Gaps or cracks in the caulk can result in regular leaks.

Inspect the caulk around your windows for gaps or damage and reapply it as needed. Regular maintenance of caulking can help maintain the integrity of the window seals.


Bad Glass Seal

A failing glass seal can lead to water seeping between the panes of glass. This not only causes leaks but also reduces the window’s energy efficiency.

In cases of a bad glass seal, consult a professional for window repair or replacement. Adding a paint seal around the glass, which overlaps the paint slightly onto the glass, can create an additional protective membrane to seal against moisture.


Missing Overhangs

Lack of roof overhangs or poorly angled fascia boards can result in a higher volume of rainfall hitting your windows during storms or heavy rain.

If your property lacks overhangs, consider installing gutters and downspouts to redirect rainwater away from your windows. Ensure that fascia boards are angled correctly to direct water away from the window frames.


Leaking Walls

Sometimes, window leaks may not be directly related to the windows themselves. Stains at the top of the window frame may indicate that the leak originates from the walls.

To solve this issue, inspect the walls surrounding the window for gaps, cracks, or damaged sealant. Repair and reseal any problem areas to prevent further leaks.


For New Window Installation, Warmable Can Find You An Installer And Free Quote

If you are considering new window installation in your property, get in touch with Warmable today. Our platform works by connecting you with an expert fitter in your area. We have an extensive network all across the UK.

Simply fill in our simple online form and a member of our team will promptly call back to schedule an on-site visit. You will be offered a free, no obligation quote. Should you choose to accept your offer, work can get started as soon as possible!

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