Foundation waterproofing

Protect your building against moisture and infiltration with Fondabec

Water is one of the worst enemies of foundations. When it seeps through concrete walls or the footing, it can cause serious damage: cracks, spalling concrete, chronic humidity, mould, and a loss of property value. To avoid these problems, it is essential to protect your building with effective and durable foundation waterproofing.

At Fondabec, we operate across Quebec to carry out exterior waterproofing work using the best membranes on the market, suitable for poured concrete or block foundations. Whether preventive or corrective, our team offers tailor‑made solutions adapted to local soil conditions.

Why waterproof a foundation?

Soil moisture, water infiltration and freeze–thaw cycles exert constant pressure on your foundations. Without adequate protection, water can seep into the concrete, causing cracks, damp patches, mould and degrading the basement environment.

Foundation waterproofing, also called foundation sealing, is an essential intervention aimed at protecting the building’s structure over the long term by blocking any penetration of water from outside. It is particularly recommended when replacing a French drain, repairing a crack or refurbishing the footing.

In what cases should you waterproof your foundation?

Waterproofing a foundation is not only recommended for new construction. It becomes necessary as soon as water threatens the integrity of the footing or signs of dampness appear in the basement. It’s important to act quickly, because neglected infiltration can lead to significant repair costs.

Here are the most common situations in which exterior waterproofing should be considered.

Water infiltration in the basement

If you see water at the base of walls, puddles after heavy rain or persistent damp in the basement, it is likely that water is seeping directly through the foundations. These infiltrations often come from hydrostatic pressure on the exterior walls. A waterproofing membrane applied to the exterior of the concrete acts as a watertight barrier, preventing water from penetrating.

Poor drainage around the building

Poor soil drainage, caused by an uneven terrain, an ineffective or absent French drain, or poorly compacted clay soil, can lead to water accumulating against the foundation. This prolonged pressure accelerates concrete deterioration and increases the risk of infiltration. In these cases, combining a waterproofing membrane with a new French drain is the ideal solution.

Presence of cracks or degraded concrete

Cracks in the footing, whether fine or wider, are direct entry points for moisture. Even after interior sealing, soil pressure can reopen them or create new ones. Exterior waterproofing with an elastomer membrane strengthens the foundations and protects the concrete in the long term, especially for block foundations, which are more porous than poured concrete.

Major construction or renovation

During major works such as a drain replacement, an extension or a basement excavation, the foundation is partially or fully exposed. This is therefore the ideal time to carry out exterior waterproofing before backfilling. This approach extends the durability of the building without having to excavate a second time later.

The advantages of exterior waterproofing

Among the different sealing techniques, exterior waterproofing is the most complete and durable. Unlike temporary solutions carried out from the inside, it acts directly on the source of the problem: water that exerts constant pressure on the foundation walls.

It is the method favoured by experts when conditions allow, whether for an existing house or during new construction. Here are the main advantages of this approach.

Complete protection against water and humidity

A well‑installed waterproofing membrane creates a watertight barrier between the soil and the foundation, preventing any water infiltration, even under high hydrostatic pressure. This protects not only the concrete walls but also the inside of the building: basement floor, insulation, materials and furniture. The result is a dry, healthy basement with no musty odours.

Preservation of the integrity of the concrete or block

Concrete is a porous material that absorbs water over time, especially if it was not protected during construction. In the case of block foundations, which are even more vulnerable, water can quickly seep between the joints. Applying an elastomer or multi‑layer membrane stops this infiltration and significantly slows the premature ageing of the concrete.

Increase of the lifespan of the foundation

A waterproofed foundation ages much better than a foundation left bare in wet soil. By preventing internal concrete erosion, moisture migration and repeated freeze–thaw cycles, you extend your footing’s durability by several decades. This also saves you from costly long‑term repairs (underpinning, crack repair, foundation replacement).

Waterproofing solutions used by Fondabec

There is no single way to waterproof a foundation: each building and each soil type require an adapted approach. At Fondabec, we select the best techniques and materials available based on the condition of the concrete, the soil’s moisture level and the terrain configuration. All our solutions are designed to ensure long‑lasting protection against water infiltration while complying with building codes and industry best practices.

Elastomer membrane applied hot or cold

This involves applying a liquid or sheet elastomer membrane directly onto the cleaned foundation wall. Once in place, it forms a continuous, flexible and resistant barrier capable of absorbing ground movements without cracking. It is particularly effective on block walls and protects against long‑term moisture penetration.

Self‑adhesive or multilayer membrane with drainage panel

For some projects—especially on very porous walls or during major renovations—we use a combined solution consisting of:

This approach offers double protection: complete sealing and efficient management of runoff around the foundation. The drainage panel directs water towards the French drain, reducing the pressure on the membrane.

Integrated peripheral drainage

Successful waterproofing also relies on effective perimeter drainage. If the French drain is absent, clogged or poorly installed, water pressure around the house remains high despite an effective membrane.

That’s why Fondabec also offers to install or replace the French drain, including:

This complementary intervention maximises the effectiveness of the waterproofing system and provides long‑term peace of mind.

A doubt or a question concerning an infiltration?

For more than 20 years, Fondabec has been assisting homeowners in Greater Montreal and across Quebec with their foundation waterproofing projects. Whether you’re in Laval, Longueuil, Terrebonne, the North Shore, the South Shore or another region, our team travels quickly to assess your situation and propose the most durable solution.

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

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FAQ

How much does it cost to waterproof a foundation?

The price depends on several factors, including the length of foundation to be treated, the type of membrane used and site accessibility. An on‑site assessment is necessary to determine an exact cost.

What is the difference between waterproofing and sealing?

Both aim to block moisture, but waterproofing works in depth, using exterior membranes. “Sealing” sometimes refers to more superficial (interior or temporary) solutions.

Can a foundation be waterproofed in winter?

In general, waterproofing work is carried out in spring, summer or autumn, when the ground is not frozen. However, certain interventions can be planned in winter if conditions allow.

Is it possible to waterproof a foundation from the inside?

Some cracks can be sealed from the inside, but this does not replace complete exterior waterproofing, especially if water comes from deep in the soil.

Which membrane is the most effective?

An elastomer membrane is one of the most durable and resistant to ground movements. However, the final choice depends on the type of foundation, the budget and the condition of the concrete.

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

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