Repairing a residential drain or foundation

Foundation cracking

Possible causes of cracks in the foundation include:

• poor-quality concrete;
• a construction defect;
• poor soil conditions;
• improper drainage, etc.

Consult a building waterproofing contractor , who can tell you whether the crack is stable or not (e.g., because of ground movement) and proceed with repairs. By choosing a certified contractor, you can be assured of a job well done.

Seal the crack from the inside (polyurethane injection)

Though sealing from the inside may require removal of interior finishing, this solution is usually less expensive than tackling the problem from the outside.

Solution:

• Inject liquid polyurethane sealant to the full depth of the crack. The soil outside acts like a plug to keep the product from overflowing. 
• Pros:
• This corrective action can be taken even if the crack is wet.
• The product retains a degree of elasticity, so watertightness is maintained even if the foundation shifts slightly.
• Cons:
• The seal is durable only if the concrete is of good quality.
• Good to know:
• It may also be necessary to fasten steel stabilizing plates to the wall on either side of the crack to minimize shifting during freeze/thaw cycles.

Seal from the outside (installation of a waterproofing membrane)

If the foundation is unstable, only an exterior membrane will guarantee a waterproof seal.

Solution:

• Begin by digging a trench along the foundation wall, approximately 3 feet (1 m) wide. The contractor must be licenced to perform excavation (Licence 2.5). For the sealing part of the job, they must hold Licence 7.
• Widen the crack using a radial saw, and fill it with epoxy cement or another sealant product.
• Cover the area around the crack with waterproofing membrane at least 30 inches (75cm) wide, extending all the way to the footing (to properly cover the joint between it and the wall).

Waterproofing work: take advantage of the Rénoclimat program

As of 2016, foundation waterproofing work done by qualified contractors is eligible for the Government of Quebec’s RénoVert refundable tax credit. The current grant amounts are in effect since May 1, 2024:

• These amounts are applicable if your post-retrofit energy evaluation was conducted after May 1, 2024.

• If your post-retrofit energy evaluation was conducted before May 1, 2024, the amount to be paid will be calculated based on the previous grant amounts.

To learn more: Rénoclimat

No drain

If your house was built before 1950, there may not be any foundation drain at all; few residential construction companies at the time installed them. Your property may happen to have excellent natural drainage capacity. Eventually, though, you could start to see signs of inadequate drainage. At that point, installing a drain may be the best solution.

Defective, collapsed or blocked foundation drain

Entrust the work to a contractor qualified in excavation and lot grading (Licence 2.5). This expertise will be invaluable both for diagnosing the problem correctly and performing the actual corrective work. 

Drain inspection by camera

For an accurate assessment, the expert will examine the drain using a video camera connected to a monitor. Depending on the situation, they will access the drain via the cleanouts (vertical tubes running from the ground to the drain pipe), the floor drain / sump pit, or the storm sewer line. If this is not possible, one or more trenches will have to be dug outside.

Solutions:

• Unblock the drain using water pressure: Sometimes, cleaning with a high-pressure washer may be enough.
• Partially repair the existing drain: If only part of the drain is blocked, it can be restored to working condition.
• Completely replace the foundation drain
• As this is a major project, get quotes from two or three different contractors.
• The work requires excavation and may take several days or weeks. The final grading can only be done the following year, as the soil needs time to settle. The return on investment, however, is worth it: stability, comfort, increased properly value, and peace of mind for a long time!

Indoor drain

Sometimes, excavating around the house is problematic or impossible. In such cases, installation of an indoor foundation drain can be considered.

Solution:

• Saw into the basement slab around the walls, to a width of approximately 12 inches (30 cm), creating a trench.
• Connect the trench to an indoor sump pit, with a sump pump installed (see next section).
• Protect the inside of the foundation walls with a drainage membrane to intercept water.
• Install the drain pipe, fill in with gravel, cover with new cement, and finish the walls.

Sump pit

A sump pit (essentially, a basin for collecting water) may also need to be installed if you regularly experience water seeping into the basement through the slab (i.e., the water table rises frequently). In some cases, the sump pit can serve to collect the water from the foundation drain. 

Solution:

• Break the slab and dig a square pit approximately 2 feet (60 cm) deep.
• Line the bottom with gravel and fit a sump box with a perforated bottom into the pit.
• Install a sump pump to keep the water level well below the slab.

Warning: 

1. Check your municipal bylaws before doing the work. The sump pit should discharge the water into the city storm drain, with any excess water pumped through an overflow pipe that leads outside, well away from the foundation.
2. Beware of radon! Be sure to install an airtight container over the sump pit. This will also prevent unpleasant odours and keep insects away.

Sump maintenance

Your sump pit needs to be cleaned every year. The drainage water brings in earth and sand, which can prevent the pump from operating properly.

• Check that the pump is working properly, and check for debris that could be keeping it from drawing water.
• Pour some fresh water into the sump pit from time to time so that the pump comes on and discharges standing water (this will help prevent odours).
• If the sump pit is connected to the storm sewer, use the cleanout to check that the backwater valve between the sewer line and the sump pit is working (make sure the valve closes properly).
• Call in an expert if you notice that the water is rust-coloured. The drain may be at fault!