Crack in a window corner

Cracks in a window corner or under your windows are very common in the walls of a home. They can even happen very quickly after your wall is built. Before proceeding with the repair of the window seal, it is necessary to know how to define the origin of the crack and its characteristics in order to ensure that they will not reappear.

Crack Formation Under Windows: A Guide to Repairing Window Seals

Where do cracks under windows usually appear?

It is not uncommon to see a crack in a window corner. Usually, it will appear at the top of the window, and in 50% of cases, another one will form at the bottom.

The most common cracks under your windows are shrinkage cracks, often vertical, that appear a few months after the construction of your façade is completed. As it cures, concrete shrinks and begins to crack, most often under your windows. It is not uncommon to observe shrinkage cracks in foundations.

Cracks under windows in foundations

Concrete foundations with windows have a propensity to crack in these specific areas. In fact, each window decreases the strength of the concrete and creates a void in the foundation, making it more vulnerable.

The danger is that any foundation crack can let moisture through or can let water in. This problem can worsen and create a real risk for your organization.

On the outside of your foundation wall, you may discover that the concrete is covered with plaster. Plaster can have many more cracks than your foundation under the windows actually contains. To find out if there is a real crack in the concrete, you will need to remove the plaster and check that the crack does not continue below ground level.

Our expertise at your service

You will be able to benefit from all the expertise of Groupe Fissure Expert and see all the difference in quality existing on our repairs!

For any question or repair on the cracks in your home, contact one of our experienced technicians at Groupe Fissure Expert inc.


What repair should be done for your cracks under windows?

To repair a crack in a window corner, our team of experts uses the technique of high-pressure injection of flexible polyurethane or the installation of an elastomeric waterproof membrane.

High Pressure Injection of Flexible Polyurethane

First and foremost, we drill holes along the crack at intervals of 4 to 12 inches (10 to 30 cm), at a 45-degree angle, to reach the crack in the middle of the foundation wall. Then we clean the holes and the crack. Subsequently, we seal the crack on the surface with epoxy plastering, and then we insert mechanical metal injection ports into each of the holes. Finally, we inject the flexible polyurethane at high pressure along the entire length of the crack, from the bottom to the top.

Installation of elastomeric waterproof membrane

To install a waterproofing membrane, we start by cleaning and preparing the crack on the surface, before sealing it with various high-performance polymer-based sealants. We then apply a primer to the foundation to receive the waterproofing membrane, and we finish by laying it, before sealing the perimeter of the membrane with an elastomeric bitumen.

The Fissure Expert Foundation Group’s guarantee of durability

At Groupe Fissure Expert Fondation, we are committed to offering you the best possible expertise to meet your needs, while ensuring that we establish a lasting, respectful and courteous relationship with our customers.


To avoid any problems with your cracks under the windows and to be sure to get a complete, fast and lasting repair , remember to contact one of our technicians as soon as possible. Only Groupe Fissure Expert Fondation will ensure lasting repairs over time.

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FAQ Window Gasket Repair: Preventing Home Sagging and Its Risks

Window Corner

What is the connection between repairing window seals and house sagging?

The link between repairing window seals and house sagging is to prevent water infiltration. Poorly maintained windows or windows with defective seals can allow water to enter under the windows, compromising the home’s foundation. Infiltrating water can soften the soil beneath the foundation, causing the structure to gradually subside. Untreated water damage can lead to moisture, mold, and severe structural damage. Thus, repairing window seals plays a crucial role in preserving the strength of the home.

What are some signs of house sagging that I should look out for in relation to my windows?

In relation to windows, signs of house subsidence include windows that become difficult to open or close due to deformation of the structure. Cracks that form around window frames can be an indicator of ground movement under the house. Windows that are no longer level or have uneven spaces in relation to the frames are also signs to look out for. These signs can indicate foundation problems due to water seeping under the windows.

How can I prevent my home from sagging by maintaining my window seals?

To prevent house sagging, it is essential to keep window seals in good condition. This includes regularly inspecting the joints for any signs of aging or deterioration. If the joints have cracks, holes, or show signs of aging, it is recommended that they be replaced. In addition, make sure that the window sealing is adequate to prevent water infiltration under the windows. Regular maintenance of windows can help preserve the integrity of the home’s structure.

What should I do if I notice signs of sagging in my house in relation to my windows?

If you notice signs of house sagging related to your windows, it is recommended that you call a foundation repair professional. These experts can assess the situation in detail, identify the underlying causes of the subsidence, and offer repair solutions specific to your situation. These measures may include repairing the foundation, reinforcing the structure, and correcting window sealing problems. It is essential to deal with these issues quickly to avoid further deterioration.

What are the potential risks if I neglect to repair window seals in the event of a house subsidence?

Neglecting to repair window seals in the event of a house collapse can lead to significant risks. Water infiltration under windows can soften the soil under the foundation, which can compromise the stability of the structure. This can lead to safety issues for occupants and significant structural damage. Long-term repair costs can also be considerable. In addition, moisture and mold problems can affect indoor air quality and occupant health. By neglecting to repair window seals, you risk compounding problems and leading to greater costs and inconvenience in the future.