How To Stop Water Leaking From Aluminium Windows

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Looking after your home, especially during inclement weather conditions, can be challenging. This is why it is essential that you invest in high-quality windows that are designed to last for a long time.

High-quality windows and proper installation can help to prevent window leaks, and the material of your window frames will also play a big part in how long they should last and how often they must be maintained.

This article will explore the main causes of a leaky window and give you the hints and tips necessary to resolve the issue.

Common Causes of Window Leaks

There are multiple benefits to installing an aluminium window frame. As well as offering excellent security, thermal efficiency with low U-values, and a range of aesthetically pleasing styles and colours, aluminium window frames can withstand heavy rain and wet conditions when properly installed.

Aluminium is a versatile material that can be extruded to meet functional and structural needs. Unlike wood frames, you don’t need to worry about aluminium frames rotting.

Unfortunately, there can still be instances where windows leak. Being able to source the cause and, if possible, repair the cause of the leaky window can help to save you the cost and inconvenience of having to replace them.

The following examples can lead to leaky windows and the problems that a leak can bring.

Poor Installation

New windows should last a significant amount of time before you should have any concerns about performance. If your new windows start leaking, you should look into your warranty.

Using reputable installers is important, and you should only consider carrying out an installation project if you have the relevant experience.

Old Property

Older homes can settle and shift slightly, and this can cause alignment issues which can lead to small gaps around the window frame.

Sometimes the design of the building or other problems can be the cause of a leak and not the window. A poor overhang or structural damage can be a bigger problem that you will need professional help to resolve.

Sealant Issue

Damaged window flashing, caulk, or sealant around the edge of the glass can result in the seal being broken. This can allow moisture to get in and compromise the surrounding area.

Failures in the Gutter System

The majority of aluminium windows will have a gutter system that is designed to catch and remove water.

A sill or flashing can be used to protect the window and allow the water to drain. The following issues are most common in gutter system failures;


Penetrating the gutter system can compromise its performance, even if it is sealed afterwards.


Gutter systems also use joins along the system. These splices can leak if they aren’t sealed to allow possible movements, with the correct joint design in mind, or properly joined to the window’s perimeter caulk.

Gutter Termination

Gutters can be a great way to transport moisture from the window. However, proper consideration must go into where it is taken.

Gutter termination must be considered in the bigger picture of architectural design and window installation to ensure the water can be carried away without causing problems elsewhere.

End Dams

Poorly installed end dams can cause issues with containing water. The end wash or sealant that connects adjacent constructions with the end dam should be designed to direct water to the gutter. Both of these have to work together to avoid leak risks.

Gutter Water Height

Gutter water levels can be affected by how heavy rainfall is, wind, and interior and exterior pressure differences. This can lead to a leaking window.

How to Locate Window Leaks

Locating the cause of a leaky window can be more challenging than it seems. Carrying out regular checks can also help to diagnose and fix issues early on, helping to stop them before they develop into big issues.

One of the best ways to detect where a window leak is coming from is by trying to detect where the air is coming through.

This can be done more easily on windy days, where you can feel the wind coming through.

Alternatively, using a heat measuring device to alert you to the leak or gap can be an easy way to determine where water can get in.

Repairing a Leaking Window

When it comes to window leaks, prevention is better than repair, so taking the time to regularly check and clean can make a significant difference.

Clearing the window and guttering from dirt can minimise the risk of clogging or further issues. If you do find a leaky window, the following advice should help you to fix it;

Replacing Caulk

Step 1 – Remove Existing Caulk

You will be able to remove old caulk from the space between the window and the frames using a knife or spatula. A plastic spatula will minimise the risk of scratching your aluminium frame or the glass.

If you do end up scratching it, then knowing how to remove scratches an aluminium window frame can be useful information to have, which you can find out in our guide.

Step 2 – Prepare the Caulk for Application

Choosing a butyl rubber caulk is best for working with plastics, mortar, metal, and aluminium.

You should also invest in a caulk gun for a smooth and level application on your window.

Step 3 – Evenly Apply the Caulk

Move at a steady pace applying a steady level of pressure to the caulk gun trigger.

Ensure you completely seal any leaks and apply the caulk along the frame part. This will help to minimise the risk of further damage or leaks.

You will be able to smooth the caulk using a spatula to ensure you get a good finish that blends in well with the surrounding area and looks good.

Replacing Weather Stripping

Weatherstripping is used to seal the openings of windows and minimise the risk of water getting through gaps.

If your weather stripping is damaged or worn out, it can lead to leaks.

Follow these steps on how to seal aluminium windows with weather stripping;

Step 1 – Remove the Damaged or Worn Out Weather Stripping

You should be able to cut out the existing weather stripping so you can pull it out completely.

Step 2 – Clean and Dry the Area

Fully cleaning and drying the area before applying your fresh weather stripping is essential. This will allow you to get a flush seal and start from a good position.

Step 3 – Measure the Area

Measuring the area so you can cut the perfect length is essential. Too short, and you will have to start over or risk a gap between stripping.

If your stripping is too long, that is easier to deal with as you can trip it down. However, you should never try to just cram it in. This can cause it to bunch and will break the seal.

Step 4 – Apply the New Weather Stripping

Applying the new weather stripping properly will help you enjoy a leak-free, draught-free, and energy-efficient home.


How do I stop rainwater coming in through my window?

Check your window for any leaks, and fix them using the methods explained above. You can also use silicone or latex to plug any noticeable leaks.

Why is water coming in through my window?

A leaky window is most commonly a result of the sealant breaking down, allowing water to enter your home.

Buying Aluminium Weatherproof Windows

Buying modern windows will typically provide you with secure, energy-efficient, and weatherproof options.

Our website offers an excellent way for you to explore our weatherproof aluminium windows that will provide excellent performance for years.

You won’t need to worry about a leaking window when investing in our high-quality product range.

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