Can you sell a house with mould in Quebec?

Can you sell a Quebec house that has mould?

Yes. The articles on the warranty of quality do not make cleaning, or any other work, a condition of the sale. You can sell the house as it stands. What the sale does not skip is saying what you know. A defect the buyer has been told about is not a hidden one. Article 1726 says the seller warrants that, at the time of the sale, the property and its accessories are free of latent defects which render it unfit for the use for which it was intended, or which so diminish its usefulness that the buyer would not have bought it or paid so high a price. The seller is not bound to warrant a latent defect known to the buyer, or an apparent defect. An apparent defect is one a prudent and diligent buyer can perceive without an expert (Civil Code of Québec, article 1726).

Québec.ca says the signs of mould or of excess humidity are stains, often greenish or black, on walls, ceilings or carpets, around windows or in closets; a characteristic musty or earthy smell; and water marks, buckling, peeling or other signs of water infiltration, which can indicate a problem concealed behind the materials. It says air or surface analysis is usually unnecessary when mould is visible or those signs are there. The step it names is a careful look for the cause. It says standing water, infiltration or water-soaked materials favour mould, and that a water damage should be cleaned and dried completely within 24 to 48 hours, after which mould can develop. It says surfaces larger than 1 m², or that are numerous, hard to clean, or that return after cleaning, are a case for a specialized firm, and that indoor humidity is usually kept between 30% and 55% so condensation does not form. The page was updated on 30 November 2022 (Reconnaître et éliminer les moisissures dans la maison). Those sentences describe the house. They are not a condition article 1726 adds to the sale. Water through a foundation is a separate question (Can you sell a house with foundation problems in Quebec?).

What must the seller’s declaration say about mould and water?

On a brokerage sale, the form Déclarations du vendeur sur l’immeuble is obligatory for the sale, by a natural person, of a chiefly residential immovable of fewer than five dwellings, including one held in divided co-ownership or in undivided ownership. Divided co-ownership has its own form. If that seller refuses to give the information or to sign, the broker cannot represent them. The copy of the residential form read for this page is marked V24, June 2022. The answers are given to the best of the seller’s knowledge and in good faith. The seller provides the available documents that support them, and the details go in section D15: the place, the year, how the situation was dealt with, and whether it is resolved (Déclarations du vendeur, form DV, PDF).

The questions that bear on mould are numbered. D4.1 asks whether there has ever been water infiltration, and the basement or crawl space, the roof, a window and a door are among the places. D7.1 asks whether significant, regular condensation has formed in winter, on windows, walls or the ceiling. D7.2 asks whether there has ever been a foul smell, and dampness is one of the answers. D7.3 asks whether there have ever been traces of mould, rot or fungi, on windows, walls, the ceiling, or elsewhere. D13.1 asks whether the immovable has been inspected and whether those reports can be provided. D13.2 asks whether other tests or expert reports have been done, and air quality is one of the items named. D14.5 asks whether any other element could affect the value, the income, the expenses or the use. The OACIQ’s public page, dated 18 June 2019, says water damage or infiltration must be declared even when it has been corrected, with the corrective work and the invoices and other supporting papers. Once the form is signed it is annexed to the promise and given to the mortgage lender, so the lender can determine, with that knowledge, the terms of the loan it may grant the buyer. It is also given to a building inspector who asks for it. If a significant detail was left out, or the situation has changed, the seller tells the broker and completes the Modifications form, which is obligatory in that case (Le CV de la propriété, page in French).

A sale with no broker does not use that form as a listing requirement. The OACIQ rule that makes the form obligatory is a rule for brokerage sales. You may still put what you know in writing. What still binds you is the Civil Code, which is the subject of How do you sell a house without a real estate broker in Quebec?.

What changes when you knew about the mould?

“Known to the buyer” and “known to the seller” are not the same sentence. Article 1726, above, is the buyer’s knowledge: a defect the buyer already knows, or can see without an expert, is not warranted. Article 1728 is the seller’s knowledge. If the seller was aware of the latent defect, or could not have been unaware of it, the seller is bound not only to restore the price, but also to make reparation for the injury the buyer suffered (Civil Code of Québec, article 1728). Article 1727 says that if the property perishes because of a latent defect that existed at the time of the sale, the loss is borne by the seller, who must restore the price. If the loss results from superior force, or from the buyer’s fault, the buyer deducts the value of the property in the condition it was in at the time of the loss (Civil Code of Québec, article 1727).

Article 1729 is a presumption, and only for a sale by a professional seller: a defect is presumed to have existed at the time of the sale if the property malfunctions or deteriorates prematurely compared with identical property, or property of the same type. The presumption is rebutted if the defect is due to improper use by the buyer (Civil Code of Québec, article 1729). Article 1730 binds the manufacturer, any person who distributes the property under their name or as their own, and any supplier, including an importer (Civil Code of Québec, article 1730). The article names those persons. It does not name the owner who sells their house.

Éducaloi’s page on a latent defect opens with mould in the walls, a foundation that is crumbling, and water entering a basement, as what a buyer may find after the purchase, and it says these may be latent defects. It says the seller is responsible for a latent defect even when the seller did not know it was there, and that the seller must tell the buyer about defects the seller knows. The seller may not lie about a defect, omit an important fact in order to induce the purchase, or dress the facts up so the buyer pays a higher price. It says that disclosure lets the buyer ask for a lower price or negotiate, because some defects can diminish the value (Le vice caché dans un immeuble, page in French). On the buyer’s side, Éducaloi says a written notice to the seller is obligatory as soon as possible after the discovery. It says a reasonable time depends on the circumstances, including the time needed to identify the defect and measure how serious it is, and that six months to a year is generally treated as reasonable, and can be longer when the defect shows only in a season. It says not to start the work, unless it is urgent because the defect is dangerous or threatens serious damage or the loss of the building, so the seller can see it (Étapes à suivre en cas de vice caché, page in French).

Does a sale without legal warranty cover mould you knew and hid?

No. Article 1732 says the parties may add to the legal warranty, diminish its effects or exclude it, but in no case may the seller exempt himself from liability for his personal acts or omissions (Civil Code of Québec, article 1732). Article 1733 says a seller may not exclude or limit liability unless the seller has disclosed the defects they were aware of, or could not have been unaware of, and which affect the right of ownership or the quality of the property. The same article makes an exception where a buyer buys at their own risk from a seller who is not a professional seller (Civil Code of Québec, article 1733).

Éducaloi gives mould in the walls as an example of a hidden defect the warranty can cover, and it says the warranty is normally automatic. It says the buyer cannot invoke it for a problem the seller declared, or for what a pre-purchase inspection, an up-to-date certificate of location, or a notary’s land-register search could reveal. The promise and the deed must then say the sale is made “without any legal warranty, at your own risk.” The buyer has to be told before signing, and can try to negotiate the clause. If the warranty is excluded, Éducaloi says a claim for a latent defect is no longer open. The remaining path is to show that the seller deliberately hid the truth about an aspect so important that the buyer would not have bought, or would not have paid the same price (Immobilier : acheter sans garantie légale, page in French). The OACIQ tells the seller’s broker that the waiver will not protect the seller against an action for defects of which the seller was aware and which should have been disclosed. The OACIQ also strongly recommends that brokers no longer use the phrase “without legal warranty at the buyer’s own risk,” because that complete exclusion cuts off warranties from earlier sellers as well. It prefers a partial clause that names the warranty excluded, the warranty of quality, and the sellers excluded, the immediate seller only (The legal warranty of ownership and quality). The Chambre des notaires says the clause has to be drafted so it is not ambiguous, that sellers can never avoid their personal liability, and that a professional seller can never be relieved of defects they were aware of, or could not have been unaware of, and did not reveal. It says that where the sale is without warranty and the seller is not a real estate sales professional, the transaction is entirely at the buyer’s risk, and it tells that buyer to have the building inspected and to negotiate the price to compensate for the lack of recourse (What is a sale without legal warranty?). A promise that simply has no inspection condition is not that clause. How the clause is written is the subject of Selling a house as-is in Quebec.

What do the health pages say, and what do they not say?

The Québec.ca health page, also updated on 30 November 2022, says moulds are fungi invisible to the naked eye. They can form colonies where there is excess water or humidity and enough nutrient, such as cardboard or gypsum board. A small area that is cleaned quickly is generally not a particular problem. Significant growth disperses particles that can be breathed and that can cause health problems. The page lists irritation of the eyes, nose and throat, a runny nose, sinus congestion, cold-like symptoms, wheezing, cough, more frequent or more severe asthma attacks, chronic fatigue and headaches, and it says the same symptoms can come from other indoor contaminants. It names people with allergies, asthma or a chronic respiratory disease, infants and young children, older people, and people whose immune system is weakened as more at risk. It says to consult a health professional, or to call Info-Santé 811, if you think the symptoms come from mould (Problèmes de santé causés par les moisissures). This page does not add a diagnosis.

The INSPQ says the main condition for fungal growth is available water, whether from chronic infiltration, excess humidity, surface condensation, a broken pipe or a flood. It says persistent excess humidity and fungal contamination are undesirable because they can damage materials, alter indoor air and cause health problems for the occupants (Les moisissures dans les bâtiments). Its note on the position of health bodies says there is currently no exposure guideline for mould inside non-industrial buildings, that corrective measures are recommended whatever the species, and that air-test results cannot be used to assess the occupants’ health risk because there is no guideline. Santé Canada’s recommendation, as that page quotes it, is to control humidity, to correct a leak or a water infiltration quickly, and to clean mould growing in a residence thoroughly, whether or not it is visible (Position des organismes, page in French).

The CMHC page Mould in Housing says mould grows when it has moisture and nutrients, that dampness inside a material can be enough even when no water can be seen, and that a musty or earthy smell often means mould. It says small areas can be cleaned by the occupant, with the precautions on that page, and that medium and large areas should be cleaned by people who are professionally trained (Mould in Housing). The same organization’s guide on moisture and air says mould itself does not cause damage to the structure of a house, and that it is a sign of moisture conditions that may eventually rot wood framing and corrode structural steel (Moisture and Air). None of these pages states a price for the work. This page states none.

Is mérule the same thing as a patch of mould?

No. Québec.ca, on a page updated 17 February 2026, says mérule, or Serpula, is a macroscopic fungus that feeds on wood. It breaks the wood down and the wood loses its structural properties. The page says the presence of mérule or of other wood-eating fungi is a serious problem when it is not controlled quickly. It can develop in buildings that are poorly maintained, that do not meet construction standards, or that are subject to water infiltration, for example a broken water line, water through the roof, or a foundation problem. It grows quickly in confined places without ventilation, where there is water or humidity. Prevention is what the page calls the best way to limit contamination, or at least to reduce the damage and the cost of decontamination and of putting the building back. It tells future buyers to have the house inspected and, where the report says so, to follow up before concluding on the expert work it recommends for mould and water infiltration (Quoi faire en cas de mérule).

The same page says the Bureau de normalisation du Québec has published the first standard used as a reference for assessing contamination by mérule pleureuse and for rehabilitating the building where that is the case. The work is in two stages: an investigation, which checks whether mérule is there, how far it has spread, what it has damaged and what caused it, and then the decontamination. The owner has to use people who have the expertise to advise, who hold the required licences and insurance, and who belong to a professional association, corporation or order. The page names it as standard BNQ 3009-610, Contamination des habitations par la mérule – Investigation et réhabilitation du bâtiment, which can be downloaded free of charge. On the seller’s declaration, traces of mould, rot or fungi are the question at D7.3, and D14.5 is the question for any other element that could affect value or use.

What does an inspection change, and what do the insurer and the lender see?

Éducaloi says the law does not require the buyer to hire an inspector, and that the buyer does have to be prudent about apparent defects. A pre-purchase inspection is a visual examination. It does not open walls, it does not guarantee that there is no latent defect, and a serious finding can be a reason to negotiate the price or to withdraw the offer. Éducaloi says these inspectors hold a residential building-inspector certificate from the Régie du bâtiment du Québec, and that category 1 covers houses, condominiums and residential buildings of six dwellings or fewer (L’inspection préachat, page in French). On a brokerage promise, the OACIQ says the broker must recommend a full inspection, and that refusing one can matter later if a court asks whether the buyer was diligent (L’inspection, page in French).

On insurance, only what the pages say. The AMF says water infiltration through the roof or the basement, and sewer backup, are not covered unless extra protection was bought, and that the consequences of a flood are generally excluded, though an insurer may offer coverage for some of those situations (Assurance habitation). The Bureau d’assurance du Canada says a home policy usually covers sudden or accidental water damage from interior plumbing, heating or air conditioning, and damage inside the house from water coming through a roof leak, while damage to the roof from wear or poor maintenance is not covered (Protection contre les dégâts d’eau et les inondations, page in French). Neither page names mould. This page will not say a policy pays for it, and it will not say an insurer must refuse the house.

On a loan, the only sentence the OACIQ page supports is the one already quoted: the signed declaration is given to the mortgage lender so the lender can determine, with that knowledge, the terms of the loan it may grant. The pages cited here do not say that a lender must refuse a house because of mould. A mapped flood zone is a different question (Can you sell a house in a flood zone in Quebec?).

Which dates, reports and invoices do you hand over?

The form’s own list is the list: the invoices, warranties, plans, specifications, permits, reports and notices that support the answers, and the D15 note of where, when, how the situation was dealt with, and whether it is resolved. D13.1 is the earlier inspection reports. D13.2 is the tests, including an air-quality test, and whether you can provide them. The OACIQ says a history of water damage is declared even after the corrective work, with the invoices. The papers a Quebec closing needs besides these are in What documents do I need to sell a house in Quebec?. None of those pages, and not this one, states a price for the work.

Can you list it, exclude the warranty, or sell directly as it stands?

Yes to each, and they are not the same promise. Listing with a broker is the path that uses the declaration above, including D7.3 and the papers in D15. Selling without the legal warranty is the clause in article 1733, on the promise and the deed, and it does not cover a defect you knew and did not disclose. A direct sale is a third path: one buyer, no brokerage contract, and no showings.

A promise that still depends on an inspection, or on a loan, can reopen the price or end when the report names the mould. A direct buyer who takes the house as it stands, and whose offer has no inspection condition, is not that promise. The duty to say what you know is the same, and an offer with no inspection condition does not, by itself, set aside the legal warranty of quality. That depends on the warranty clause in the deed, which the notary reads.

Bruce Malcolm buys houses himself on the Island of Montreal and the surrounding areas. He holds no broker, agent or appraiser licence, and he is not an advisor. There is no inspection and no commission. An offer with no inspection condition does not, by itself, set aside the legal warranty of quality. You say what you know about the mould and any water infiltration when you send the address: where it was, when, and any report or invoice you already have. The closing date is one you choose once the notary can sign. Sending the address starts a conversation (request an offer). The form does not commit you.