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How to Repair Cracked Foundation Walls

Last modified: 2021-07-22 | Approximate reading time 7 mins

Léa Plourde-Archer

Have you noticed a crack in your home's foundation walls? Are you hoping to repair it before it gets worse? presents the ideal solutions to renovate your home's foundation.

Fixing cracks in your foundation

Types of foundation cracks

Active cracks

Fissure fondation

From the outset, let's specify that there are two types of cracks: active or passive. An active crack is an unstable crack that can grow over time, due to weather conditions or movements coming from the ground or from the house itself. 

Montreal newspaper La Presse shared these tips to recognize an active crack: In order to know if a crack is active, during the summer you should either measure it with a ruler, mark its current size with paint on the foundation’s surface or install tape next to it.

Passive cracks

Come springtime, these references will show you whether there was a change or not. In other words, this mark serves to show the size and current location of the crack. After a freeze and thaw cycle, you can go back to see if it has changed considerably or if it has stayed the same. In the event that very little change has happened, you may have yourself a passive crack. This type of crack is less likely to expand over time.

It is a relatively stable crack that may have been caused by a faulty application of the cement or by shrinkage, which can affect this type of material. Since this type of crack doesn’t tend to grow over time, once they have been stabilized (in the first two years after the house has been built), they don’t need to be repaired on the spot.

In a  nutshell, a proper inspection of the foundation walls is key so as to make sure that the house remains in good condition and it will also be essential when looking to get a specific diagnosis for cracks, which will then be fixed in order to minimize the possibility that they will reappear later on.

Apart from the factors mentioned above, others may also lead to cracks including:

  • Groundwater movement ;
  • The type of soil on which your foundation rests;
  • The use of lower quality concrete ;
  • Weather conditions when laying concrete.

How to repair foundation cracks?

With regards to the type of material used to renovate your building, know that this is an extremely important step in making your foundations weatherproof.

In general, polyurethane and flexible epoxy are the best products to fulfill the needs of your foundation. For example, polyurethane is known for being very flexible. Further down in the article, we will discuss these products in more detail.

Cracks in foundations

Two options are available for this type of task: working from the inside or from the outside.

In an article titled Alerte à la fissure! (Beware of the crack- translation ours) by Simon Diotte, published in La Presse, the author states that not everyone agrees on which is the best method: “Concerning the best method to repair cracks, our meetings with different experts lead us to notice that opinions vary from one person to another. Many believe that repairing a crack from the inside is a temporary solution and that for a more long-lasting fix, it is better to work from the outside. However, André Gagné disagrees with this point of view “Both methods are good. It depends on the conditions” (editor’s note: André Gagné is the director of technical expertise for the APCHQ, the Quebec builders association).

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If the crack is small, it is possible to work from the inside. However, if the damage is more extensive and the crack is clearly active, it may be better to repair it from the outside, which is also more costly due to the fact that it involves an excavation process. It all depends on the crack and on your budget! In general, you can find a solution that costs a few hundred dollars.

Don't forget to hire a certified professional that will be able to select the best technique to fix your cracked foundation problem.

réparation d'une fissure dans les fondations_Soumission Rénovation

Products to be used to fix foundation cracks


Amongst the most well-known are epoxy and polyurethane. Here are some things you should know about these products. This is what Wikipedia has to say about epoxy: “Epoxy is a term used to denote both the basic components and the cured end products of epoxy resins, as well as a colloquial name for the epoxide functional group.

Epoxy resins, also known as polyepoxides, are a class of reactive prepolymers and polymers that contain epoxide groups. Epoxy resins can be made to react (cross-linked) either with themselves through catalytic homopolymerization, or with a wide range of co-reactants including polyfunctional amines, acids (and acid anhydrides), phenols, alcohols and thiols.”

In common language, the word epoxy is used to designate a type of glue that will be used to fill out a crack. However, if the epoxy is rigid, in the event that the house is still moving, chances are that another crack will end up forming close by, although, in theory, this should not happen.

Epoxy does not alter the appearance of the building and can be used from the inside. By employing this technique, the process will not require a ground excavation near the site of the crack, which means that there won’t be a need for heavy machinery, thus reducing the risk of damage caused to the building.


Polyurethane is a highly resistant sealant product that is characterized by its exceptional durability, strong resistance against tears and its ability to sustain movements that amount to ±25% compared to its original situation (Source: LePage glue).

This product is also much more flexible than epoxy and it has hydrophilic properties, which means that it reacts to water. When this happens, the elements form a waterproof coat that fills the crack, forming a strong bond. Therefore, this product is very useful to prevent water ingress problems.

A hydraulic pump is used to inject the polyurethane into the crack. This process ensures that the product penetrates well through the whole crack, up to its deepest point. It doesn’t only fill the surface! It must, however, be known that these products have their limits and that they are only for cracks of certain sizes.

Furthermore, according to Simon Diotte, if a crack measures more than 1/8 of an inch, another solution will have to be found, as a simple sealing will not be enough. You’ll have to ask a contractor for their opinion about what should be done.

Main steps for repairing concrete cracks from outdoors

Fixing a foundation

When you decide to repair cracks in your foundation, if you and your contractor decide to repair from outdoors by using the injection techniques, here is a breakdown of how things usually go:

  • First, you need to excavate the work areas (manually or with machines);
  • Next, you will have to brush the foundation walls to remove particles from the ground and disaggregated concrete;
  • With this done, you will then have to drill holes at a 45-degree angle to insert the injectors;
  • You can then inject high-pressure flexible polyurethane to fill the cracks;
  • Don't forget to clean inside the crack with clear water in order to make it humid;
  • If necessary, you will then install steel plates or bar clamps on the foundation cracks;
  • Following this, go ahead and install a waterproofing membrane to block water infiltrations;
  • Lastly, you will only have to refill the working areas.

Tools and products for injection repair

In order to implement the previous repair method, you will need the following tools and products:

  • Polyurethane ;
  • A hydraulic pump ;
  • Some shovels ;
  • A rigid bristle brush
  • A drill ;
  • Water ;
  • Steel plates or clamps ;
  • A waterproofing membrane.

The cost of repairing foundation cracks with the injection technique

fissure sur fondation_Soumission Rénovation

When the cracks are filled in, this product will act as a control joint. Concerning epoxy, this is a strong glue that will act as soldering on your foundations. Lastly, know that this repair method could vary from a few hundred dollars to more than $1000 in some cases, excluding any damages done to the building's exterior siding.

However, it should be noted that the injection technique does not work for all situations. Cracks that measure more than 1/8 inch often require repairs that are more complicated. 

Get 3 renovation quotes for your cracked foundation walls can help you get quotes for your cracked foundation walls. If you submit your project to us, we’ll put you in contact with the most suitable contractors for you. Fill in the form on our homepage (only a few minutes), and you will receive quotes from home renovation specialists.

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