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Renovation tips

6 min read

How to Repair Cracked Foundation Walls

Renovation tips

6 min read

How to Repair Cracked Foundation Walls

Renovation tipsHow to Repair Cracked Foundation Walls

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

Fixing Cracks in Your Foundation

Types of foundation cracks

Source: Canva

Active cracks

From the outset, let's specify that there are two types of cracks: active and passive. An active crack is an unstable crack that can grow over time. Such cracks can be caused by subsidence, frost, or inadequate drainage. Since these problems can compromise the stability of your home, they warrant your full attention.

Montréal 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." In other words, label where the location of the crack, as well as its size, and after a freeze-thaw cycle, go back and check the size of the crack to see if it has changed substantially or if, in fact, it has remained about the same.

Passive cracks

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 it has been stabilized (in the first two years after the house has been built), it won't require repairs on the spot.

In a  nutshell, a proper foundation wall inspection is key to make sure that the house remains in good condition and it will also be essential when looking to get a specific diagnosis, which will then be fixed to minimize the possibility of reoccurrence down the line.

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 leak-proof.

In general, polyurethane and flexible epoxy are the best products to carry out foundation work. For example, polyurethane is known for being very flexible. Further along in the article, we will discuss these products in more detail.

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) by Simon Diotte, published in La Presse, it is stated that not everyone agrees on which method is best: “Concerning the best method to repair cracks, our meetings with different experts have led us to believe 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 APCHQ's Director of Technical Expertise (Association of Construction and Housing Professionals of Quebec).

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 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.

Products Used to Fix Foundation Cracks

Source: Canva


Epoxy and polyurethane are amongst the most well-known. Here are some things you should know about these products. Wikipedia states that epoxy is a term used to denote both "(...) the basic components and the cured end products of epoxy resins. Epoxy resins, also known as polyepoxides, are a class of reactive prepolymers and polymers which contain epoxide groups. (...) Epoxy resins may be reacted (cross-linked) either with themselves or with a wide range of co-reactants including polyfunctional amines, acids (and acid anhydrides), phenols, alcohols and thiols (...).”

In layman's terms, the word epoxy is used to designate a type of glue that will be used to fill in 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 noted 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 sufficient. You will then have to ask a contractor for their opinion about what should be done.

For more information, check out our article: Concrete Crack Repair: Epoxy or Polyurethane?

Main Steps to Repair Concrete Cracks from Outside

When you decide to repair cracks in your foundation, if you and your contractor decide to repair them from outside by using 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 scrub 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 clean water to dampen the cavity;

  • If necessary, you can then install steel plates or bar clamps on the foundation cracks;

  • Following this, go ahead and install a waterproofing membrane to block water leaks;

  • Lastly, you will only have to backfill the working areas.

Injection Repair Tools and Products

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

  • Polyurethane;

  • A hydraulic pump;

  • Shovels;

  • A rigid bristle brush;

  • A drill;

  • Water;

  • Steel plates or clamps;

  • A waterproofing membrane.

Cost of Repairing Foundation Cracks Using Injection Techniques

Source: Canva

When the cracks are filled in, this product will act as a control joint. In terms of 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 $1,000 in some cases, and that is without accounting for any damages done to the building's exterior siding.

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

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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Last modified 2023-11-10

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