Practical Guide
Adapting a Home for Aging in Place in Quebec
Your mother wants to stay in her house. The three front steps have become an obstacle, and so has the bathtub. The …
The shed you buy at the hardware store fits in a box, and nobody at the cash asks for your address. Your address is exactly what decides everything, though: permitted floor area, height, distance from the lot line, permit or no permit. Here is where the rule is written, city by city, and what happens when the structure is already standing without paperwork.
Construction accessoire: the term that decides everything
A shed, a storage building, a detached garage and a permanent detached carport all belong to the same regulatory family. Montreal calls them dépendances, Laval calls them constructions accessoires, accessory structures, and the borough of Rivière-des-Prairies-Pointe-aux-Trembles calls them bâtiments complémentaires. The word changes, the logic does not: their use has to stay accessory to the use of the main building.
The Info-permis sheet for Rivière-des-Prairies-Pointe-aux-Trembles draws the consequences. A main building must already exist on the lot, and the accessory structure has to be detached from it: attaching it to the house turns it into an extension, held to stricter standards. You may use it as a garage or as a storage building, but not to live in, and a trailer, a temporary shelter or a shipping container cannot stand in for one.
The central point fits in one sentence: the numbers do not come from the province. They come from the zoning by-law of your city or your borough, and they differ from one street to the next.
When a shed permit becomes mandatory in Laval and in Montreal
In Laval. A permit is mandatory for any construction accessoire with a ground footprint equal to or greater than 18 m², that is 193 sq ft. Below that threshold, no permit is needed for a storage shed, but the rules of the Code de l’urbanisme, the planning code, still apply. One exception: a permit can be required whatever the size if the property is subject to a plan d’implantation et d’intégration architecturale, a site planning and architectural integration programme, which the Info-règlements tool indicates by address.
A garage and a permanent detached carport have no threshold at all: Laval writes that a permit is mandatory for their construction, full stop. The published fee is $92 for the first $20,000, plus $2.50 per $1,000 bracket or part of a bracket, and the announced processing time is 30 days.
In Montreal. The common threshold is 15 m², and analysis fees run $9.80 per $1,000 of work, with a minimum that varies. But the word “common” does all the work here, because the borough decides:
| Borough | Permit required | Max height | Distance from lot lines | Minimum fee |
|---|---|---|---|---|
| Saint-Léonard | Always, one shed only | 3.05 m | 0.45 m | $133 |
| Ahuntsic-Cartierville | Over 15 m² | 4 m | 1.5 m | $167.40 |
| Rivière-des-Prairies-Pointe-aux-Trembles | Over 15 m², or 25 m² in total | 4 m | 0.6 m | $259.90 |
Saint-Léonard adds a limit the other two do not have: a maximum length or width of 4.6 m. In other words, the same 14 m² shed goes up without a permit in Ahuntsic-Cartierville and requires a certificate of authorization in Saint-Léonard.
Shed or garage: what zoning limits on top of the permit
The permit is only the front door. Zoning then imposes constraints that plenty of owners discover after delivery.
Siting. A bâtiment complémentaire cannot be installed in the front yard, meaning the space between the front lot line and the main facade extended to both side lot lines. On a corner lot or a through lot, the setbacks of the other yards facing a public road apply as well.
Distance from the lot line. In Rivière-des-Prairies-Pointe-aux-Trembles it is 0.6 m from every line, unless the exterior cladding is masonry, in which case the building may be sited right on the line. Even then, runoff, snow included, has to fall on your own land.
The relationship with the house. This borough’s zoning provides that the area of each bâtiment complémentaire may not exceed 50% of the area of the main building, and that its height may not exceed that of the main building, up to a maximum of 4 m. Lot coverage, for its part, adds the house and every accessory structure together, and varies by zone.
For Laval, no single value for setbacks, area or height is published for the whole territory. The extracts of the Code de l’urbanisme on storage sheds and on the detached carport can only be read zone by zone, inside Info-règlements: “Recherche par lot ou par adresse” button, your address, then “Voir les détails”. Do not transpose a Montreal number onto a Laval lot. The reading method itself is the one in land value and zoning.
The temporary carport and its dates
The winter shelter escapes the permit, but not the calendar, and the calendar is not the same on both sides of the river.
| Laval | Montreal | |
|---|---|---|
| Authorized period | October 15 to April 30 | October 15 to April 15 |
| Permit | None | None |
| Outside the period | Structure removed | Metal structure fully dismantled |
In Laval, the shelter has to sit on the same lot as a residential building, and be installed on a driveway, a parking area or a parking space, never on a normally grassed surface. Minimum distances from the public road are published as four diagrams, depending on whether there is a sidewalk, a curb, both or neither.
In Montreal, the dates still vary by borough: Mercier-Hochelaga-Maisonneuve allows October 1 to April 30. The tarp has to be synthetic, white and translucent, on a dismountable metal frame, and a shelter located less than 3 m from the sidewalk must carry a window of at least 0.5 m² on each of its sides. Installation is prohibited in a heritage sector.
A non-compliant accessory structure is not just a neighbourhood annoyance. In Laval, failing to comply with the Code de l’urbanisme lets inspectors demand corrective work, and the published fine for a natural person is $400 for a first offence and $800 for a second.
What new construction changes on the assessment roll
The property assessment roll is filed every three years, but it is kept up to date between filings. Montreal puts it this way: the rolls must reflect the changes made to properties, and the update applies retroactively to the date the work ended, without going back further than the fiscal year preceding the current one. You then receive a notice of alteration setting out the reasons. It is the Loi sur la fiscalité municipale, the municipal taxation act, that requires this.
A nuance: among the work Montreal cites as liable to increase value are renovating a kitchen or a bathroom, an extension and finishing a basement. The shed is not on that list, and no official source puts a figure on the effect of an accessory structure on a value entered on the roll. Remember the reference date too: for the 2026-2027-2028 rolls, the market conditions used are those of July 1, 2024. A notice that strikes you as off market can be contested, and contesting your municipal assessment follows a precise deadline. Before the job starts, a home value estimate gives you the point of comparison.
A missing shed permit: what the resale reveals
This is where the file resurfaces. The Déclarations du vendeur sur l’immeuble form, the seller’s declarations on the property (DV 00001, version V24 06/2022), asks question D2.11: since you acquired your property, has there been any addition, replacement or modification, in particular of windows, a pool, a shed, a sidewalk, a paved driveway, fences, a porch, a deck, hedges, retaining walls or others?
The form adds an explicit note: if the answer is positive to questions D2.8, D2.9, D2.10 and D2.11, a new certificat de localisation may be required if the one provided does not reflect those changes. The 2026 suggested tariff guide of the Ordre des arpenteurs-géomètres du Québec, Quebec’s order of land surveyors, sets the suggested fee for a certificate of location on an urban single family home at $1,630.00, disbursements and taxes extra, each surveyor remaining free to charge more or less.
Two other boxes follow. D2.12 asks whether you have ever received a notice of non-compliance from an insurance company, the municipality or the government. D2.13 asks whether an insurer has ever refused to insure the property in whole or in part. A garage built without a permit has an unfortunate habit of producing both.
Laval, for its part, already requires a recent certificate of location, prepared by a land surveyor, among the documents for a detached garage permit application. The document you file at the counter is the one that will serve at resale.
Insuring a shed or a detached garage
The guide Tout connaître sur l’assurance habitation, published by Info Assurance, sets out the principle: if you are an owner, your home insurance covers the house and its outbuildings, shed and detached garage included. The amount required for the building corresponds to the cost of rebuilding it if it were entirely destroyed, an amount that often differs from market value and from the municipal assessment.
No official source, on the other hand, sets a general percentage of coverage for outbuildings. That limit exists in many policies, but it belongs to the contract, not to a public rule: read yours before you build. A non-compliant structure that was poorly declared is exactly the kind of detail that makes a home hard to insure.
Frequently asked questions
My shed is already there and I never had a permit. What now? First check whether the structure meets the current standards for your zone, through Info-règlements in Laval or at your borough permit counter in Montreal. If it complies, bringing it into order remains possible. If not, the inspector can demand corrective work. Either way, question D2.11 is waiting for you at the sale.
Does a temporary carport count as an accessory structure? No, and that is why it follows its own dates. The Rivière-des-Prairies-Pointe-aux-Trembles sheet does prohibit using a temporary shelter as a year-round bâtiment complémentaire.
Will the new garage push up my tax bill? The Loi sur la fiscalité municipale requires the roll to be kept up to date, and the alteration is retroactive to the end of the work. No official source puts a figure on the increase in advance: wait for the notice of alteration, then compare.
The seller says the shed is under the threshold. How do I check? Measure the ground footprint and compare it to your city’s threshold, 18 m² in Laval and 15 m² in most Montreal boroughs. Then ask for the certificate of location: if it predates the construction, it shows nothing, and that is already an answer.
To go further, read the seller’s declaration form and cutting down a tree and the property rules.
Planning a shed, a garage, or a sale with an undeclared structure? Write to me: we look at the permit file and the certificate of location before the buyer does. Service in French, English and Arabic.
Georges Matar
Residential Real Estate Broker · RE/MAX DU CARTIER INC.
Contact Georges
