French Drain installation steps

When the time comes to replace a French drain, there are several checks to be made to ensure that the installation is in compliance and will age well over time. Here is how a typical French drain replacement job goes:

Step 1 – Excavation of the foundation perimeter:

We must excavate all areas affected by our work. We use every precaution to minimize the impact on existing features.

We can install plywood boards to protect the paver or a particular layout. We also have specialized shoring systems to reduce the width of our excavation when the area is restricted. All our employees are trained to respect the CNESST standards during excavation. Our priority is to have a safe working environment throughout the project.

Step 2 – Cleaning the foundation:

Once the excavation is complete, we proceed to clean the foundation with a high-pressure water jet. This step is crucial because our products will not adhere to a poorly cleaned foundation that still has debris on it. Once the foundation cleaning is complete, we can establish a game plan for repairing foundation cracks, holes that need to be filled, as well as any anomalies that require special intervention.

Step 3 – Foundation repair:

Before applying our membrane, we must repair any imperfections in the foundation. If it is a foundation crack, we must determine if it is a shrinkage crack, movement or a structural problem. Each crack must be treated seriously and meticulously. We use polyurethane or epoxy based injection products as needed. Often old foundations need to be resurfaced in places to make them smooth and uniform. If it is a minor repair, we use hydrolic concrete while if it is a question of a missing fill in the foundation, we must use a repair mortar containing fiber inside. This specialized mortar will restore the strength to the missing portion of the foundation.

Step 4 – Membranes application:

Now that the foundation is ready to be waterproofed, we can spray our membrane on it. We are using the Premium Rubber Membrane from Cantex. This high quality elastomeric membrane has proven itself in our climate, it remains flexible, applies well and makes the foundation waterproof for decades to come. We apply 2 coats of this membrane in order to obtain the manufacturer’s mandatory thickness.

Upon application, the membrane has a brown color and we can tell it has finished drying when it is completely black. Once dry, we apply the Delta-MS drainage membrane. This membrane accentuates the drainage of the foundation and creates a physical barrier between the earth and the elastomeric membrane. The latter will be sealed at the top with finishing strips and sealant to ensure its watertightness.

Step 5 – French drain installation :

The installation of the French drain is the crucial part of the whole work. We have to adapt according to several factors among which

• the height of the water table
• the nature of the soil in place
• the presence of iron ochre
• the pressure of the soil on the drain after backfilling…

Each of our installations exceeds the requirements of the building code and this is probably the reason why our customers love our work. The installation technique described in this paragraph takes into account the nature of the soil, namely: an unpaved area with stable sandy soil, a non-problematic water table that varies according to the season and the absence of iron ochre.

We install a geotextile membrane at the bottom of the trench in order to filter the sediments that could be transported with the water table. The 4” BNQ rigid drain will be placed on this geotextile membrane. Many contractors simply place the drain at the bottom of the footing without taking into account the height of the interior floor, this is the biggest mistake most often made.
The building code specifies that the top of the drain must be below the underside of the basement slab. Our crews know how to check the installation to ensure that the foundation drainage system will be compliant and effective. We then cover the 18” French drain with 3’4” net stone and cover this stone bed with another geotextile membrane to filter the runoff water. Access stacks to the French drain will also be installed at strategic locations to allow for cleaning or inspection of the drain in the future.

Step 6 – French drain evacuation:

The water that will be captured by the French drain will have to go somewhere. There are many ways to dispose of that water but we have to comply with the building code as well as municipal bylaws. Each municipality has its own standards for stormwater management. Our experts know the standards and how to guide the homeowner to have a compliant installation. The most efficient and reliable way to evacuate water from a French drain is by gravity. Unfortunately, this technique is not always possible. It is therefore necessary to install a pumping station that will evacuate the water to the discharge authorized by the city. We also offer battery powered pumping systems with emergency alarms in the event that the primary electrical system fails.

Step 7 – Backfill:

We proceed to backfill the trench. If the homeowner does not plan to redo his earthwork immediately after our work, we use the soil kept on the site to do the backfill. However, if the owner plans to hire a contractor to continue with the earthwork as soon as we leave, we must backfill the trench with crushed stone and compact it to ensure a controlled backfill. Obviously, this technique is more expensive since we have to transport all the excavated soil to a backfill site. During the backfill, we install vertical drains to receive the basement window sills where necessary. The galvanized steel coping will be installed and we finish the backfill. Before our equipment leaves, we make sure that the ground slopes are in compliance and that the water drains well away from the foundation.

Do you have a French drain installation or replacement project?

Lesage Excavation has been providing French drain installation and repair services for over 15 years. Winner of the 2020 and 2021 Consumer’s Choice Award in the foundation repair category, our expertise and customer service are recognized throughout the Greater Montreal area.

We are available 7 days a week and 24 hours a day to answer your questions.
You have 3 ways to contact us:

• Call us at (514) 219-0125
• Send an email to: info@lesageexcavation.com
• Submit your project online here

We mainly serve the Montérégie, the Greater Montreal, the South Shore, a part of the North Shore as well as Ontario; and more specifically

Vaudreuil-Dorion – Montreal – Laval – Longueuil – Brossard – Candiac – Salaberry de Valleyfield – North Lancaster – South Glengarry – Alexandria – Hawkesbury – Rigaud – Hudson – Pincourt – Notre-Dame-De-L’ile-Perrot – Lachute – Montebello

We can also travel to more remote areas when it is a complex project and the owner cannot find a certified contractor in their area.