The defining feature of North American cities is the single-family detached home. It is the least efficient way to house people, yet municipal zoning laws have historically served to ensure its primacy.

It’s time for change – and urgently so. The cost of housing in Vancouver and Toronto is stratospheric, and even in more affordable cities like Calgary, Ottawa and Montreal, it is way more expensive than a generation ago.

Expensive housing hinders economic growth. Cities are the engines of the economy but are increasingly inaccessible, and the financial challenge of moving to Canada’s biggest cities, to study or to pursue a career, is daunting.

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The high cost of housing also leaves a generation of young Canadians facing the prospect of a lifetime of renting, never able to build equity, or shouldering a worrisome amount of mortgage debt that will take decades to pay off.

There are many factors at play – British Columbia has done much to address the issue of foreign speculators – but the core problem is the allocation of land. Our zoning is forcing cities to expand endlessly outward, by preventing them from building up.

The bulk of municipal land zoned for housing – at least two-thirds of it in many cities – is reserved for detached homes, while multiunit housing is restricted to small designated areas, generally in the city core but often far beyond or on abandoned industrial lands. That leaves the supply of housing artificially limited, particularly in areas near transit lines and city centres.

Meanwhile, owners of detached homes, who have the ear of elected officials, argue the so-called character of their neighbourhoods must not be disturbed. The long-standing status quo serves them well, effectively enriching them through government policy.

But the argument about character is a smokescreen. Where there is a neighbourhood of single-family homes, there was once a forest or a field. No one mourns the lost character of what had been there before. Character is wielded as a weapon against change. As Globe and Mail architecture critic Alex Bozikovic put it in June, “'Character’ means exclusion.”

There is an answer. It’s called the missing middle: small-scale, multiunit housing, from duplexes and triplexes to mid-rise apartment buildings. The missing middle is not a fix-all, but it is an essential step forward.

Minneapolis is a beacon of possible change. Last December, city council passed a plan that ended the dominion of single-family zoning. It is regarded as the first of its kind in the United States, but it’s hardly radical. Where a single house was previously permitted, a building with three units, a triplex, is now allowed. The rallying cry has been “Neighbors for More Neighbors.”

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Oregon was the next to move. State legislators in late June passed a bill that will remake single-family zoning to allow fourplexes in cities of more than 25,000 people, and throughout the Portland region.

In Canada, the prospect of change is depressingly dim. In the City of Vancouver, a one-year trial allows applications for duplexes in single-detached zones. This is in a region where the typical house costs $1.4-million and median annual household income is $73,000. Meanwhile, city council is ponderously debating whether to get work started on a new citywide plan that will take three years to complete.

This is the opposite of urgency.

In Toronto, the story isn’t much better. The province in June approved new rules for downtown and midtown Toronto, after reworking plans the city had submitted, but the geographic reach of change is limited. There is no serious talk of rezoning what’s dubbed the “yellow belt” – the 70 per cent of available land limited to single-family homes.

The moves in Minneapolis and Oregon are interesting, but modest compared with what is needed in Vancouver and Toronto. Small apartment buildings – of three, four or five storeys – would go a long way. Then there are important questions about low-income housing and rental housing. And there’s the issue of how cities should benefit from increases in land values sparked by zoning changes.

But first we need some political will. There are 10 million Canadians between the ages of 20 to 40, the time of life when people make a first foray into home ownership. Canada’s zoning rules are antiquated. They should be rewritten to serve the present, not the past.