In 1927, Montreal city councillor Athanase David argued that future residents would judge the city for tolerating exterior spiral staircases.
Fifty years later, Montreal made the staircases legal again.
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Today they are the part tourists photograph. More important, the buildings behind them still house a huge share of the city. Duplexes, triplexes and sixplexes line blocks that feel like neighbourhoods, not development sites.
Montreal did not invent stacked flats. Boston had triple-deckers. Chicago had two-flats. McGill geographer David Hanna traced the Montreal duplex to British building types. The honest claim is better anyway: Montreal is the North American city where the plex won, spread and never quite went away.
Toronto and Vancouver chose another path. They reserved most residential land for detached houses, then concentrated new apartments on a thin strip of high-rise sites. Now Ottawa is paying cities to permit the kind of housing Montreal built before the First World War.
That should embarrass a few people.
The staircase was a spreadsheet decision
Montreal’s famous exterior stair is easy to treat as decoration. It was closer to an underwriting choice.
The Lachine Canal became an industrial corridor in the nineteenth century. Mills, foundries, shipyards and rail shops drew workers who needed to live close enough to walk to work. Lots were narrow. Builders needed more homes and more rooms on each one.
Then, around 1890, Montreal required a front setback of about three metres. Instead of giving that space to a lawn, builders put the stairs there. Moving the staircase outside preserved interior space for rooms and removed a common hallway that would have needed heat.
A straight staircase did not fit neatly into ten feet. So it got steep. Then it curved.
This is the useful part of the story. Building form is often the physical result of land price, lot shape, code and financing. The staircase was not dreamed up at a design charrette. Thousands of small builders solved the same math problem.
Montreal later tried to erase its own answer. Affluent districts restricted exterior stairs in the early twentieth century. A 1948 building code barred new curving exterior stairs. The classic triplex faded in favour of walk-ups with an interior stairwell. In 1978, the city repealed the ban, partly because the old form delivered affordable housing.
Zoning killed the stair. Then zoning brought it back.
Small builders made a big city
The plex did not need a tower site, an eight-year entitlement process or institutional capital. One landowner could build on one narrow lot.
That matters more than the architecture.
The Plateau filled with duplexes and triplexes. Rosemont grew around the Canadian Pacific Angus Shops. Verdun went from roughly 11,600 residents in 1911 to about 60,000 by 1931. Block by block, small projects added up to city-scale housing.
The owner often lived in the larger ground-floor flat and rented the units above. We now call that house hacking because every old idea eventually gets a course and a landing page. In Montreal it was simply a way for a working family to own a building without carrying the whole mortgage alone.
It also produced a different rental market. Montreal became a city of tenants and small landlords at the same time. In the 2021 Census, 63.6 per cent of households in the City of Montréal rented. That was about 519,000 renter households.
The city reached that share without covering every neighbourhood in towers.
July 1 is an operating risk
Quebec’s Moving Day sounds like folklore until you own rental property there.
Urban leases once started on May 1. Quebec changed the law in 1973 so leases no longer needed a fixed start date. During the transition, leases were extended to June 30, 1974. July 1 stuck.
The date is tradition now, not a legal requirement. Tradition is still powerful enough to create an annual crush of movers, trucks, contractors and vacancies.
For an owner, that changes the calendar. Miss the main leasing window and a vacant unit can sit. Plan a renovation badly and every trade you need may already be booked. A national underwriting template will not catch that.
Local habits belong in the model.
Toronto is paying to reverse its own mistake
Ontario’s provincial floor is three units on a serviced urban residential lot. Toronto allowed fourplexes citywide in 2023. Several cities changed their rules as part of federal Housing Accelerator Fund agreements.
The federal government committed $471 million to Toronto and about $115 million to Vancouver through that program. Ottawa also reached a $900 million agreement with Quebec, matched by the province.
Some of that money supports useful work. Sewer capacity, approval staff and standard plans are real constraints. But the broad policy story is absurd. Governments banned a common, financeable housing form across most residential land. Housing became scarce and expensive. The fix is now a multi-billion-dollar program that pays governments to unwind parts of the ban.
Ottawa’s Housing Design Catalogue includes standardized fourplex and sixplex plans. Montreal’s old pattern book was a walk down rue Saint-Denis.
The five-unit financing cliff
The modern investor lesson has very little to do with pretty triplexes. Unit thresholds change the deal.
CMHC’s MLI Select starts at five units. A project that earns 100 points for affordability, energy use and accessibility may qualify for up to 95 per cent loan-to-cost and a 50-year amortization on new construction, subject to underwriting.
A fourplex misses the program. A fiveplex can enter it.
That single unit can change the financing, equity requirement and exit options. Yet municipal rules, lot coverage, parking, servicing or fire-code costs may make the fifth unit much more expensive than the first four.
Do not design to a label. Design to the threshold that works after every cost is counted.
What I would take from Montreal
For a buyer, an owner-occupied small multi still offers one of the clearest paths into expensive housing. Rental income can help qualify the mortgage and reduce the monthly carry. The trade is obvious: your tenant also knows exactly where you live.
For an investor, lot dimensions and local rules matter more than a broad thesis about missing middle. A 25-foot Montreal lot worked because the building type, lease market and rules developed together. Copying the facade without copying the economics gets you an expensive costume.
For a homeowner, gentle density is not painless. Construction is noisy. Parking does not vanish because a planner removed the minimum. Bad transitions beside a bungalow create predictable anger. Builders who treat the neighbours as an obstacle eventually turn them into organized opposition.
For cities, the main lesson is permission. Montreal did not reach neighbourhood-scale density through one heroic project. It let thousands of ordinary owners and small builders add a few homes at a time.
The plex is not romantic. Old buildings leak. Iron stairs rust. Tenant law in Quebec is its own world. Construction costs can wreck a beautiful pro forma.
But the form survived because it solves a basic problem: how to put more homes on ordinary lots without waiting for a tower.
Montreal already ran that experiment. Toronto is spending billions to read the results.
Listen to Episode 449: Toronto Is Spending Billions to Copy Montreal’s Housing Model
Going to Montreal? Unpacking Multiplexes Montréal is November 19 at the Grande Bibliothèque.