Quick answer
Quebec has allowed accessory dwelling units (ADUs) as of right since 2024, but every North Shore municipality keeps the power to exclude its territory. Before building or buying to densify, check your town's zoning by-law and obtain a permit. If your potential is frozen locally, ImmoMulti buys your plex directly within 48 hours, with no broker.
Do you own a plex or a multi-unit building on the North Shore with a large, underused lot? Since 2024, Quebec has theoretically opened the door to gentle densification: adding an accessory dwelling unit (ADU) — a basement, an addition, a garden suite — on your lot. But between the provincial law and your permit, one major obstacle remains: municipal zoning.
Opinion column by the ImmoMulti Team. Facts are sourced; opinions are our own.
🔥 The Blunt Opinion
Let's say it plainly: gentle densification is the best wealth-building opportunity offered to the small plex owner in a decade — and too many North Shore municipalities are sabotaging it. Quebec did the legislative work. Adding an accessory dwelling on a lot you already pay taxes on means creating fresh rental income without buying a second building. That's exactly the kind of leverage a human-scale investor needs. Yet this lever stays locked until your municipal council adopts a favourable by-law — and many are dragging their feet.
Our thesis in one line
The densification potential is now written into law; the brake is no longer in Quebec City, it's at the city hall of your North Shore municipality.
What Quebec Now Allows Owners
An accessory dwelling unit — also called a secondary or additional dwelling — is a complete dwelling added on the same lot as a principal residence: a basement converted into a self-contained unit, a side addition, a converted garage or a small backyard garden suite. That is the very definition of "gentle" densification: you add housing without distorting the neighbourhood.
Since the changes to the Act respecting land use planning and development (introduced by Bill 31, in force since 2024), a Quebec municipality can authorize ADUs through a simple local by-law, without revising its entire land use plan. The Ministère des Affaires municipales et de l'Habitation has even set out a framework for this power in its planning guide.
Source: Government of Quebec — Bulletin Muni-Express, "Municipal powers in housing matters" (July 4, 2025).
The momentum has even accelerated this month. Bill 22, An Act to enhance municipal intervention powers, was assented to on June 12, 2026. It entrenches in law the ability of a city to authorize residential projects without a referendum process — measures first introduced by Bill 31.
Source: Government of Quebec — Bill 22 (June 2026).
The Municipal Lock That Changes Everything
Here is the trap few owners understand: the law gives municipalities the final say. The provincial framework applies to detached single-family homes, but the municipality can exclude all or part of its territory from its application. The result: two identical plex owners, ten kilometres apart on the North Shore, can have completely different development rights — depending on the whims of their municipal council.
The reasons cited to block are almost always the same: parking, sewer and water-main capacity, "preserving the character" of neighbourhoods, opposition from neighbours. Arguments that are sometimes legitimate, often convenient. For the owner, the verdict is identical: potential allowed by Quebec, but frozen locally.
The reflex to have before buying or building
Never assume an ADU is permitted. Check the zoning by-law of your town (Terrebonne, Blainville, Boisbriand, Saint-Eustache, Mascouche, Saint-Jérôme…) and require a building permit. The same lot can be worth a great deal more — or nothing more — depending on a single line in a municipal by-law.
Densifying Creates Value on Your Land
Why does this opinion lean so clearly toward the owner? Because gentle densification tackles the right problem. The cost of acquiring a building is exploding, financing is expensive, and construction costs jumped 49% between 2017 and 2025 (versus 17% inflation), according to the Aviseo Conseil study commissioned by CORPIQ. In that context, adding a dwelling on a lot you already own is one of the few strategies where you don't pay the premium of a new purchase: no transfer duties on the whole building, no full down payment, just the marginal cost of the unit.
Source: Aviseo Conseil for CORPIQ, reported by La Presse (June 17, 2026).
Still, the numbers have to hold up. A poorly thought-out ADU — underestimated construction cost, shaky financing, overvalued rent — can destroy your returns as quickly as it promised to improve them. Before pouring a single foundation, run the project through a deal analyzer and price the real cost with a renovation calculator. Densification is an opportunity, not a guarantee.
Read also
This zoning dynamic ties into other regulatory battles facing plex owners. Read our opinion on the assessment roll that sends your plex taxes soaring, our take on converting a plex into divided co-ownership, and our analysis of the municipal right of first refusal on a plex sale.
🎭 Devil's Advocate
Let's be honest: the other camp has serious arguments, and they shouldn't be brushed aside. Entrenching a municipal power to authorize projects without a referendum is no small thing. The Ordre des urbanistes du Quebec, reacting to the adoption of Bill 22, said it was concerned about writing an "exceptional and derogatory power in housing" into law without sufficient safeguards, raising risks to the fairness, coherence and transparency of land use planning.
Source: Ordre des urbanistes du Quebec — statement on the adoption of Bill 22 (June 2026).
And the municipal instinct for caution isn't always bad faith. Densifying a neighbourhood whose sewers, water mains and streets were designed for single-family homes can create real capacity and parking problems. A neighbour watching a garden suite rise outside their window isn't wrong to worry about their privacy or resale value. In short: the discretionary power of cities, which frustrates us as owners, is also a safeguard against poorly planned densification. You can't demand flexibility for yourself and deny it to your neighbour.
The Verdict
After weighing both camps, our position stays clear but nuanced. Gentle densification is a real opportunity for the North Shore plex owner: Quebec has cleared the provincial obstacles, and adding an ADU can turn a dormant lot into a source of income. But the opportunity is not universal: everything now plays out at the municipal level, and the discretionary power of cities — legitimate at heart — makes your potential unpredictable.
Concretely: before buying a building for its lot, or before building, verify the zoning and price the project. If your municipality blocks it and your development potential is frozen, it isn't a dead end: you can choose to free up your capital elsewhere. ImmoMulti buys plexes and multi-unit properties directly on the North Shore — no broker, no commission, with an offer within 48 hours — for owners who would rather reinvest where densification truly is permitted.
