Drains and foundations : prevention or repair?

Cracks in the foundation walls. Excess humidity. Mould. Frequent accumulation of water up against the house. Worried about these signs? Read on.

A guide to get a clear picture!

Dealing with drain and foundation issues in a house can be intimidating. This guide lays everything out for you logically.  

Don’t forget: every step of the way, CAA-Quebec is there to help. Reassuring, right?

STEP 1 – Read the signs

Indoor signs of excess humidity or water infiltration

Do you suspect issues with water infiltration in your basement? Check for the signs listed below. Most of them, if they’re there, will be easy to spot inside the house. If in doubt, don’t hesitate to call in a professional contractor, who will investigate further using moisture detection equipment and/or a thermographic camera. That way, you won’t have to knock down any walls looking for humid areas or cracks. 

Read our Tips & Tricks instalment on thermography.

Indoor signs of excess humidity or water infiltration

  • Overall humidity levels in the house (hygrometer reading constantly above 50%) — read our Tips & Tricks instalment on the topic.
  • A persistent musty or earthy odour that you notice whenever you go down into the basement.
  • Mould: “furry” or powdery deposits that have recently appeared, ranging in colour from pale green to brown or black. Careful: some may be hidden underneath a covering such as a floor or wall.
  • Whitish crystalline deposits on concrete surfaces, Known as efflorescence (see our Tips & Tricks instalment), they are a sign that moisture is seeping into the concrete, dissolving the salts that it contains, and causing them to leach through to the surface on the basement side.
  • Stains that have recently appeared on finished surfaces.
  • “Sweating” on concrete walls or the concrete slab.
  • Cracks appearing in the foundation.
  • Water pooling on the floor.
  • Orange-ish water seeping in.
  • Ochre-coloured deposits along the bottom of the foundation walls or on the slab.
  • Ochre-coloured water in the floor drain (sump pit).

Mould? Beware the health effects!

Be very careful of mould, the microscopic fungi that grow on humid materials. To develop, mould requires only moisture and organic material to “feed” on: wood, paper, carpet, etc. It releases spores, which are particles that can induce symptoms such as:

  • irritation of the eyes;
  • coughing and runny nose;
  • wheezing;
  • shortness of breath; or
  • asthma and allergic reactions.

This means you need to take action quickly!

Read our Tips & Tricks instalment on mould and other basement health hazards.

Outdoor signs of poor foundation drainage

  • Frequent and constant accumulation of water near the house.

STEP 2 – Eliminate outdoor causes

If you do see these signs, your drain or foundation might not be the culprit. They may instead point to one or more of the following problems. Read on to learn more about each one.

Inadequate lot grading

Problem: The backfilled earth around a house becomes compacted over time. If there is a negative slope, water flows toward the house.


  • Backfill and grade the lot to restore the necessary slope (at least 2% positive slope for a distance of six feet [2 m] all around the house). If the new backfill soil will extend above the waterproofed part of the foundation, that part of the concrete surface will also need to be waterproofed first.
  • Correct any other negative slope that is directing water toward the house: path, patio, driveway, etc.
  • Good to know: a 2% grade is equivalent to ¼ vertical inch (6.4 mm) for every foot (30 cm) of horizontal distance. 

Warning: Be careful that you don’t shift the problem to a neighbour’s property!

Poorly designed gutters and downspouts

Problem: Gutters that are the wrong size, improperly positioned, or broken can cause runoff water to pool around the foundation. The quantity of water coming off your roof during a storm is impressive.

Solution :

  • Repair, reposition or replace defective gutters.
  • No downspout should be connected to the foundation drain! If it is, disconnect it to prevent overloading.
  • Add downspout extenders to direct water at least six feet (2 m) away from the house. 
  • Connect the downspouts to a drainage pit.

Warning: Always disconnect downspout extenders before the onset of freezing temperatures in the fall.

Read our Tips & Tricks instalment on gutters.

What’s a drainage pit, exactly?

Also known as a dry well or soakaway pit, it’s a hole dug in the yard and filled with ¾ in. crushed stone. It’s connected to the downspout by a length of non-perforated underground pipe. The entire assembly is covered by geotextile membrane before soil and grass are replaced on top.

Poorly located trees

Problem: Some trees, if located too close to the house, can lead to formation of cracks in the foundation. In dry periods, especially if the soil around the house is clayey, the roots can retain water, which can then put pressure on the foundation.

Solution :

  • Cut down potentially harmful trees.
  • Avoid planting similar trees too close to the house.

Warning: Poplar, willow, elm, red maple, Manitoba maple, silver maple and bur oak trees near the house are to be avoided at all costs.

Read our Tips & Tricks instalment titled Trees near the house.

Improperly sealed basement windows

Problem: Windows that are too close to the ground tend to develop leaks.


  • First check for cracks around the window frames and apply sealant as needed.
  • Install a window well around every window that is less than eight inches (20 cm) above the ground.

Warning: If the window can be used as an emergency exit, then the window well must not prevent a person from exiting.

Window wells: good to know

The bottom of the window well must be filled with gravel, and there must be a vertical drain pipe to direct water to just above the foundation drain, without being directly connected to it. Protective mesh to keep out debris is advisable, and all window wells must be cleaned regularly to ensure they work effectively.

Presence of iron ochre

Problem: In iron-rich soil that is in contact with water and air, deposits of iron ochre (also called ferrous ochre) can form. They are recognizable by their rust colour. These deposits can end up blocking the foundation drain.

Solution :

  • Inspect the drain using a video camera
  • Take a water sample and have it analyzed.

Warning: This is a job for an expert. There are several possible remedies: add an indoor drain, lower the water table, or (the most frequent solution) replace the flexible corrugated fondation drain pipe with one made of smooth-walled PVC pipe with large circular openings.

STEP 3 – Have the drain and the foundation repaired

If you’ve performed all of the previous steps but you still have problems, you need to explore the possibility of cracks in the foundation or the basement slab, and/or damage to the drain. This section describes the most common problems along with their solutions.

Waterproofing work: take advantage of the RénoVert program

As of March 17, 2016, foundation waterproofing work done by qualified contractors is eligible for the Government of Quebec’s RénoVert refundable tax credit. You have until March 31, 2018, to sign a contract entitling you to the credit. Find out more on the  RénoVert Web page Ouvre un lien externe dans une nouvelle fenêtre.

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 (this specialty is included in RBQ Licence 7), 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 (75 cm) wide, extending all the way to the footing (to properly cover the joint between it and the wall).

Drain damage

The normal lifespan of a foundation drain, also known as a French drain or perimeter drain, is about 40 years. Your drain may have deteriorated to the point that it no longer does is job of collecting and discharging water from the soil around your house’s foundation. Problems with a defective drain will be most noticeable after abundant rainfall and during thaw periods.

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! On this topic, see Step 4  Excavating? Use the opportunity to do preventive work!
    • Also read Foundation drains: problems and solutions.

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. Read our  special report on radon.
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!

STEP 4 – Excavating? Use the opportunity to do preventive work!

The excavation work for a foundation drain is quite inconvenient for the occupants of a house, not to mention expensive. It’s a good idea to take advantage of your “big dig” to have other work done to prevent future problems—and the need to dig again in the future. This section explains all you need to know about:

Ensuring the foundation walls are waterproof

The tar sealant originally applied to the outside of the foundation walls below ground can be upgraded. There are three possibilities:

  • A spray-on liquid elastomer coating; ideal for irregular surfaces, it forms a continuous rubber-based waterproof barrier.
  • A roll-on adhesive elastomer membrane. It is elastic, durable and self-sealing, and resistant to small stones as well as slight shifting of the foundation.
  • A drainage membrane. This is a dimpled-plastic sheet that is fastened to the foundation with concrete nails, and directly water straight down to the drain, preventing hydrostatic pressure on the walls. Combined with one of the membranes described above, it can act as a second barrier.

Insulating the basement walls from the outside

Unless your basement is already finished and insulated, excavation provides a good opportunity to insulate the foundation from the outside.

  • Consult an expert on the subject. There are products available that meet the existing Quebec energy-efficiency requirements for residential construction. 
  • This solution may increase the volume of your foundation walls, with a possible esthetic impact on the junction between the foundation and the exterior wall cladding.

Improving backfill quality

Problems with water pooling on your property can be exacerbated by poor backfill quality. Proper backfilling includes:

  • A generous coating of gravel to properly cover the drain, covered in turn by:
    • a layer of granular earth; and, above that,
    • a layer of water-resistant soil, e.g., clay.

Replacing the water inlet and sewer lines

Replacing a water inlet and sewer line is usually expensive, because it has to be done in an emergency. So why not take advantage of the machinery and labour already being there, and save money?


Are you in an emergency situation? Is there a foot of water in your basement? You have to act fast, and properly. The procedure for restoring the basement will depend on what kind of water it is and where it came from. Rainwater or snowmelt, for example, will be easier to deal with than water from a sewer backup or a river that has burst its banks.

There are three steps to a proper response:

If there is flooding, put safety first

Make sure there is no risk of electrocution.

  • Wear rubber boots.
  • Cut the power to the flooded parts of the house.
  • Unplug all appliances and other electrical devices there.

Report the incident

First your insurer, then the city, and then other resources!

Your insurer

Report the damage to your insurer immediately, following these few steps. Visual evidence (photos, video) can be very useful to help the insurer rapidly assess the situation. If, for example, you have home insurance with CAA-Quebec and you took the “Water damage” option when you bought your policy, you are covered for water damage.

  • Get authorization quickly to proceed with removal of framework, insulation, as well as wall and floor coverings.

Read this advice from

CAA-Quebec’s home insurance expertsPDF file – 34 KB

Municipality and utilities

Report the incident, if need be, to the municipality as well as to any utilities/providers affected (e.g., Hydro-Québec, Gaz Métro, phone company).

Proceed with post-disaster work

Quick action is required to limit the damage. For best results, entrust the work to experts.

Take action within 48 hours

This will ensure that mould does not proliferate on surfaces and in voids, crevices, etc. If you decide to mop up the initial damage, make sure you wear rubber gloves and boots, a breathing mask, and safety glasses to guard against contamination.

Entrust the clean-up job to an expert firm…

It is highly recommended that you hire a reliable post-disaster clean-up company, especially if decontamination is needed. They have the knowledge and equipment necessary to act effectively and limit the impacts. If necessary, they will demolish water-damaged gypsum wallboard and flooring to speed up the drying-out process.

… and the restoration as well!

Once the basement is cleaned, you can start rebuilding yourself, if you want. But consider the benefits of doing business with a company that has a general contractor’s licence: the work will be guaranteed, completed in a timely manner, and compliant with the required codes, with your home’s full property value maintained.

In conclusion

In this guide, we’ve presented a logical approach to dealing with problems that are not always easy to address. Several of the situations described require major work, for which you shouldn’t hesitate to call in professionals.

CAA-Quebec Residential Advisory Services are there to help you find the right contractors for the job, and to answer any questions you may have in case of doubt!