Foundation underpinning

Transform your basement or stabilise your home with Fondabec

Whether you want to stabilise an old house, correct a settlement or gain living space, underpinning is a reliable, durable solution adapted to buildings in Quebec.

When should you consider underpinning?

Underpinning is a structural solution used when existing foundations no longer meet the needs of the building or the current project. Whether for safety, stability or renovation reasons, this work allows you to intervene directly beneath the structure without complete demolition. Here are the most common situations where underpinning is recommended.

Stabilise a weakened or unstable foundation

When your building shows signs of settlement, significant cracks or rests on unstable soil (clay, backfill), underpinning reinforces the existing base without demolition, and it is essential to prevent long-term structural damage.

Gain living space without rebuilding

If you want to dig a new basement, create a rental unit or transform a crawl space into functional space, underpinning allows you to expand downwards without altering the exterior structure, while increasing the value of your property.

Protect your building during a neighbouring site or excavation

In urban areas or when adjacent work is taking place, underpinning protects and stabilises your building before, during or after neighbouring excavation, often in combination with retaining walls or piles to prevent differential movement.

How do underpinning works proceed?

Each underpinning project is unique. Fondabec’s approach combines structural safety, respect for the existing building and engineering adapted to Quebec’s soils. We work with certified structural engineers to ensure every underpinning project complies with provincial standards.

Here are the key steps in a project:

Structural diagnosis and soil study

Development of engineering plans and specifications

Temporary stabilisation of the building

Actual underpinning work

Waterproofing, drainage and finishing

Techniques used for underpinning at Fondabec

There is no single way to carry out underpinning; several techniques are adapted according to the foundation’s condition, soil type and project objectives. At Fondabec, we use the most reliable and proven methods, while respecting existing constraints and current safety standards. Here are the main approaches we implement.

Localised underpinning beneath the foundation

Used to locally reinforce a load-bearing wall or sunken footing. A new concrete block is installed beneath the existing foundation, generally with a support pile. It’s ideal for correcting partial settlements.

otal excavation beneath the building

A more complex method that allows a full basement to be dug or the entire foundation to be replaced. Work is carried out in sections (alternating work zones) to maintain building stability. It is recommended for houses without a basement or with a crawl space.

Addition of driven or jacked piles

When the soil is unstable or the load too great, foundation piles are installed to provide a solid footing. The piles are driven to refusal (rock or dense soil) and anchored to the structure. This long-lasting structural solution is often combined with underpinning.

What are the benefits of underpinning?

Underpinning is more than a technical solution: it’s an opportunity to optimise the value, safety and potential of your building. Whether to prevent damage, correct settlement or gain new living space, this intervention can transform your property for the long term. Here are the main advantages to consider.

Durable structural stabilisation
reinforcement or correction of existing foundations
creation of additional living space without raising the building
avoids complete demolition
significant property value enhancement

Do you need a permit or an engineer for underpinning work?

Yes. In Quebec, any underpinning or excavation project beneath an existing building requires

Fondabec assists you in all administrative steps, from planning to obtaining permits.

Need to expand a dwelling or replace a foundation?

For over 20 years, Fondabec has helped homeowners in Greater Montreal and throughout Quebec with their underpinning projects. Whether you are in Laval, Longueuil, Terrebonne, the North Shore, the South Shore or rural areas, our team travels quickly to assess your situation and offer the most durable solution.

We hold all the certifications required in excavation, civil engineering and underpinning, and we work with partner engineers and surveyors to guarantee compliance and quality in every project.

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FAQ

What is the difference between underpinning and a foundation replacement?

Underpinning involves working under the existing foundation to strengthen it or create new space. Foundation replacement often requires partial or full demolition of the existing wall.

Can you live in the house during the work?

It depends on the project. For localised underpinning, it is often possible. For a complete excavation under the house, temporary relocation is generally required.

What is the average cost of underpinning?

The cost depends on factors such as project complexity, excavation depth, structure and materials. We can give a more precise estimate after an initial project assessment.

How long does the work take?

The duration of an underpinning project ranges from two to six weeks, depending on the scale of the work, site accessibility and weather conditions.

For over 20 years, Fondabec has been assisting homeowners in Greater Montreal and throughout Quebec with their excavation projects.

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