Foundation Cracks in Quebec: Diagnosis and Recourses

A crack does not say what caused it. Yet it is the cause, and the cause alone, that decides whether you have a recourse, against whom, and for how long. Here is who establishes that cause in Quebec, with which document, and which regime applies depending on the age of the building.

Reading a foundation crack: what is urgent, what can wait

No official Quebec source publishes a crack width beyond which you should worry. No threshold will therefore be advanced here. What is documented is who has the right to give an opinion: in its June 2025 guide, the Ordre des ingénieurs du Québec classes among engineering mandates the act of “giving an opinion on the consequences of a crack in a foundation wall, on the cause of a floor sagging”.

On your own, you observe and you document. The City of Laval advises exactly that: photograph, note the dates the damage appeared and how it evolved, then consult an expert who will determine the real cause. The same page corrects a common reflex: roots do not pierce sound concrete, they take advantage of existing cracks. The real culprits, the City writes, are the soil, the climate or the age of the building.

What is urgent. Éducaloi recalls that a buyer must not repair at their own expense before notifying the seller, who must be able to verify the seriousness of the defect and repair it. The exception is narrow: urgent repairs, where the defect is dangerous or risks seriously damaging the immovable.

Clay, drainage, pyrite, pyrrhotite: four distinct causes

Clay that shrinks. The climate change adaptation plan of the agglomération de Montréal is blunt: it is clay soils that contract when they are dry. “Foundations can settle when clay soils dry out, causing the soil to shrink”, and that damage translates into cracks in foundations, also called foundations lézardées, which can progress into the walls. The City publishes as open data the surficial deposits geology map, which informs a citizen about the soils of a sector.

Drainage. Water that stays against the foundation is a problem distinct from soil movement. Grading, downspouts and the weeping tile are detailed in our piece on spring melt and basement water infiltration.

Pyrite, under the slab. The OACIQ describes it as an iron sulphide molecule present in backfill stone, therefore around foundation drains and under the slab of the cellar or the garage. As it oxidizes, it produces a white powder that swells and causes slab heaving and cracks in the footing wall and the partitions, sometimes several years after construction. The zones most at risk according to the OACIQ: the South Shore from Châteauguay to Varennes, the east and the west of the island of Montreal.

Pyrrhotite, in the concrete. It is in the aggregate, not in the backfill. The OACIQ specifies that it comes from quarries in the Mauricie, that its oxidation is much faster than pyrite’s, and that a petrographic analysis by a recognized laboratory is strongly recommended for every building constructed between 1996 and 2008 in the Mauricie. It gave rise to long litigation in that region, but I found no open primary source to summarize the outcome, so I am not summarizing it.

Why the pre-purchase inspection does not settle it

The Ordre des ingénieurs guide is explicit: the pre-purchase inspection report does not fall under engineering, and “since these are observations only, this service generally does not allow the cause of a deterioration or the method to repair it to be determined”. The engineer can add an opinion on causes at the client’s request, and preparing such an opinion is a reserved activity as soon as it bears on a work covered by the Loi sur les ingénieurs.

The OACIQ says the same thing from its side of the wall: “The inspection of an immovable alone is insufficient to detect with certainty problems caused by pyrite”, and “a broker cannot give an opinion on the origin of cracks. He is not a building inspector, nor a soil analysis specialist.” The pre-purchase inspection checklist flags the sign, not the cause. Since the Ordre issues no specialist certificate, verify the entry in the roll and demand a written contract.

New building: article 2118 and the five years of the warranty plan

Article 2118 of the Code civil holds the contractor, the architect, the engineer and the professional technologist who directed or supervised the work, as well as the subcontractor, solidarily liable for the loss of the work occurring within five years after the work was completed, whether the loss results from a defect in design, construction or production, “or, again, a defect in the ground”.

The mandatory warranty plan follows the same architecture. Garantie de construction résidentielle covers non-apparent poor workmanship for 1 year following acceptance, latent defects for 3 years following acceptance, and defects in design, construction or production and defects in the ground for 5 years following completion of the work. Its own example of a major defect is the one at issue here: “settling of the property caused by soil compaction, such that the foundation becomes unstable”.

The written notice decides everything. GCR asks you to write to the contractor with GCR in copy, using its notice form. The regulation requires a reasonable period; case law has retained six months for a non-urgent problem, but GCR specifies that it must not be treated as a maximum applicable to everything. If the contractor’s answer does not satisfy you within fifteen days, you open a claim file, detailed in our piece on the GCR warranty on a new home. Past five years, the RBQ points to arbitration and then to the civil courts.

Existing building: latent defect and written notice

Article 1726 warrants the buyer against latent defects that render the property unfit for the use for which it was intended or that so diminish its usefulness that the buyer would not have bought it, or would not have paid so high a price. It adds the sentence that is decisive here: “a defect that can be perceived by a prudent and diligent buyer without the need to resort to an expert is an apparent defect”. A crack written into your inspection report is therefore no longer hidden. What can be hidden is its origin and its extent, which only an expert establishes.

Article 1739 requires the defect to be denounced in writing within a reasonable time from its discovery, and it provides for the case of foundation movement: “the time begins to run, where the defect appears gradually, on the day that the buyer could have suspected the seriousness and extent of the defect”. Éducaloi places that period between six months and a year. Article 2925 then sets three years to sue, and article 2926 makes them run from the day the injury first manifests itself: three years from the discovery, not from the purchase.

A sale at your own risk, for its part, can leave you with no recourse. The conditions are detailed in our article on latent defects and your recourses, and the buyer’s guide places that step back inside the transaction. No recourse is won in advance: an engineer establishes a cause, not a judgment.

What insurance excludes, and the grant that exists in Laval

The City of Montreal writes it without hedging: “home insurance generally does not cover damage caused to houses by the settling of clay soils”, and owners assume the whole invoice. For landslides, the Bureau d’assurance du Canada is just as clear: it is not an insured risk and no coverage exists. Infiltration through the foundation is covered only with an endorsement added to the contract.

The City of Laval finances the repair, on one condition. The maisons lézardées component of the Société d’habitation du Québec’s Rénovation Québec program reimburses two thirds of the eligible work, up to $35,000 per residence. Among the criteria published by the City: a residence of 1 to 8 dwellings, the certificate of eligibility and the permit obtained before starting the work, at least $5,000 of work and the installation of at least one pile. And above all: “the causes of the settling of the foundation of a cracked house must be linked to the condition of the soil and not to a construction defect or flaw”. Read that sentence twice: the grant demands the opposite proof from the one a claim against a contractor demands, and it is the same expert report that serves both.

The most recent edition I was able to verify closed on March 21, 2025, with more than 66 owners helped since 2019. The program page now redirects to the general assistance page: call the City before counting on it.

Selling or buying with a foundation crack: what gets declared

The mandatory Déclarations du vendeur sur l’immeuble form (DV 00001, version 06/2022) leaves no room for vagueness. Section D3.1 covers soil problems, with boxes for landslide, settling, ground movement and soil instability. D3.2 covers stabilization work already done to the foundations, with boxes for piling and underpinning. D5.2 covers basement problems, with a box for cracks in the foundation. D13.2 covers tests and expert reports, naming pyrite, pyrrhotite and the foundation drain.

The verb matters: the form asks what has “already” affected the immovable. A repaired crack has affected the immovable. Section D15 serves to specify the location, the year and how the situation was settled, and the form requires supporting documents to be provided. The detail is in our article on the seller’s declaration.

On the buyer’s side, the OACIQ recommends making the promise conditional on an expert report by means of the Annexe Expertise form, and, for foundation concrete, clause E2.1, “Expert report at the buyer’s request”. It is up to the buyer, not the broker, to decide whether the results are satisfactory. Note finally sections D2.13 and D2.14, on an insurer’s refusal to insure or to indemnify: foundation movement leaves a trace there that sometimes weighs more than the crack itself.

Frequently asked questions

A fine vertical crack in my basement, is that serious? No official source publishes a width threshold, so no figure appears here. The Ordre des ingénieurs classes an opinion on the consequences of a crack in a foundation wall among engineering mandates. Photograph, date, have it examined.

Can I repair the crack before selling and say nothing? No. Section D5.2 of the Déclarations du vendeur covers problems that have already affected the basement, and D15 asks for the year and how the situation was settled. A documented repair reassures; a hidden repair becomes a question of good faith.

Will my home insurance pay for the piling? The City of Montreal writes that home insurance generally does not cover damage caused by the settling of clay soils, and the Bureau d’assurance du Canada indicates that no coverage exists for landslides. Have your own case confirmed by your insurer.

I am buying in the Mauricie: is the pyrrhotite test necessary? The OACIQ strongly recommends a petrographic analysis by a recognized laboratory for every building constructed between 1996 and 2008 in the Mauricie, and notes that financial institutions require the test before granting the loan, even after a reassuring inspection.

To go further, read the pre-purchase inspection checklist and the GCR warranty on a new home.

An engineer’s report in hand and a decision to make before your promise expires? Write to me. I do not diagnose a foundation, but I know how to read what a report changes about the price and the conditions.

Georges Matar

Residential Real Estate Broker · RE/MAX DU CARTIER INC.

Contact Georges