Open this photo in gallery In Mexico's San Pablo Xalpa district, shown before and after a major renovation two years ago, what was once dead space between buildings is now welcoming public space. Rozana Montiel Photo

For more than 15 years, César Solano and his wife didn’t let their three children go outside to play. When he left his small apartment each morning to work at the tire factory, he would hustle through the fences and gates dividing the overgrown courtyards, avoiding the shadowed corners occupied by clusters of men with face tattoos and dogs.

As with many of Greater Mexico City’s 21 million people, the Solano family lived in one of the low-rise housing complexes that carpet the valleys and hills around the city centre, in their case in the northern industrial district of San Pablo Xalpa.

A few years after they bought their apartment with a government loan in 1990, the public space outside its door became forbidding by day and terrifying by night, when the local drug trade flourished. Residents built more fences and gates, and covered their windows with iron, and that made the spaces even less welcoming. ”It was a frightening place – nobody came to visit,” Mr. Solano remembers.

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Two years ago, something changed. A team of women arrived, and spent several days asking the residents surprisingly intimate questions about how they’d prefer to spend their days and nights: “Where did you have your first kiss?” or “Where would your kids play hide and seek?” That was followed by several weeks persuading people to tear down their fences, and then a couple months overseeing the clearing, building and painting of new structures and spaces.

The gates and shadowed spaces are gone, and with them the sketchy guys. The architects built sunny, functional spaces between the trees where residents wanted to spend time together. There’s an open-air library where kids hang out and child care takes place, a resident-run gym, hole-in-the-wall stalls where people sell tacos, a place to dance at night. Two years after it was built, it looks fresher than ever, and full of people. Residents voluntarily keep it swept and secure, spending their nights gathering and talking rather than huddling inside. The working-class people who own the apartments have discovered that their property values (and the rent they’re able to collect) have risen for the first time since the early nineties.

“People want to move their families here now,” Mr. Solano says. “It’s made us want to take care of the place – people change the light bulbs and sweep the ground and paint the buildings because they feel like doing it.”

The transformation of San Pablo Xalpa was the work of Rozana Montiel, whose all-female architecture practice (itself almost unique in Latin America) has recently attracted international acclaim for its intimate, low-cost “site actions.”

Open this photo in gallery Architect Rozana Montiel. Nin Solis

Ms. Montiel’s interventions are one successful effort to confront what might be this century’s most challenging and underappreciated urban problem: the empty spaces between buildings. The majority of the world’s city dwellers now live in high-rise dwellings, and in many Western countries, immigration and poverty have become concentrated in suburban apartment districts. As a result, those dead spaces have become a lot more than an inconvenience for residents.

At her studio on the roof of an old building in downtown Mexico City, Ms. Montiel told me that the transformation began when she won a series of competitions by Mexico’s gigantic public-housing corporation for pilot projects to address the social decline and economic immobility in its housing complexes. A lot of it, they realized, was rooted in the physical design of the complexes.

She began by speaking to the residents, and asking unorthodox, experiential questions. “People told us: ’We’re really scared, we don’t do anything, we don’t know our neighbours, because we go out and we just want to run – the addicts get here and we’re very scared at night, there’s no light, the kids have no space to read or play safely.’ ”

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Open this photo in gallery Before its renovation, San Pablo Xalpa was an overgrown tangle of gates and fences. Rozana Montiel photo

Open this photo in gallery The neighbourhood was a fertile ground for the local drug trade, and a less-than-welcoming place for children or visitors. Rozana Montiel photo

It turned out to be a lot of little things they wanted: a place to do exercise, places for education, both for children and adults, a place to dance salsa, workshops, a place to play chess – and, for some, a place to have a little shop or restaurant. In sum, they wanted something like a common living room – because many families, crammed into apartments with too few rooms, were facing domestic crises and needed a safe place.

Estella Coss, a grandmother who has lived in the complex for 26 years, says it has turned the place into something resembling a village. “We get to know each other more – we each say hello, we do a lot of activities – Mother’s Day, Children’s Day, Christmas, Day of the Dead – everybody sees each other, all the time. People visit us.”

Ms. Montiel called the project “Común-unidad,” which roughly translates to “common unity.” It was, she says, not so much a matter of building something as removing impediments standing in the way of the community’s desire to come together. “We solved a lot of small things in order to change a lot.”

Open this photo in gallery Before and after the Común-unidad renovation: San Pablo Xalpa’s green spaces were barricaded off from one another, but now, the greenery is part of an open space for residents. Rozana Montiel Photo

From Beijing to Sao Paulo to Surrey, B.C., cities are facing challenges created by building forms and neighbourhood designs that might have appeared utopian when they were built in the postwar decades.



Wide courtyards and grassy expanses between apartment buildings were meant to create peaceful places removed from inner-city crowding. Winding streets and parking lots envisioned a car-centred life. Strict zoning meant that residential towers would be separated by wide spaces from any form of commerce or industry. Suburban apartment-tower neighbourhoods and “garden city” low-rise apartment neighbourhoods have, by design, relatively low population densities, usually too low to support mass transit.

From these empty gaps has flowed a suite of urban crises.

When people don’t want to leave their building – and when customers are afraid to visit the little shop they’ve opened – then they become stuck, not just physically but economically, socially and culturally. As cities in Europe and Latin America have discovered, these forms of isolation can lead to intergenerational poverty, educational exclusion, segregation, crime and sometimes extremism.







Open this photo in gallery Slotervaart, an Amsterdam neighbourhood of postwar suburbs and low-rise apartment buildings, has been a target for renovation by various governments and planners over the past 15 years, amid fears that bad urban design has led to alienation and sometimes extremism in the area. Isabel Nabuurs

Amsterdam

If Ms. Montiel’s space-filling interventions offer a uniquely intimate, quick and inexpensive solution to the constricting emptiness between buildings, you’ll find the opposite end of that spectrum in the northwestern corner of Amsterdam, which may be the world’s most ambitious and expensive effort to bring life to a residential area’s in-between places.

For more than 15 years, Amsterdam’s mayors, planners, housing corporations and architects have been radically reshaping this cluster of postwar suburbs containing 144,000 people. It’s been a stop-and-start set of projects under several administrations, interrupted by financial and political crises, involving scores of projects and hundreds of architects.

At the turn of this century, Amsterdam’s planners were forced to realize that the “garden city” apartment districts that had been considered an ideal bedroom community for factory workers in the 1950s and ’60s had turned into places that left newcomers and their descendants trapped outside the economic and social life of the city – and in a place too thinly populated to thrive.

“It was a green area, but that meant that the population density, especially around the lines of public transit, was very low – so it became a rather vague public domain,” Maurits de Hoog, Amsterdam’s chief planner, told me. “So the challenge for the next decade, in this vague zone, is to introduce urbanity – to introduce busy streets and parks and more public life. It should make this area more accessible for people from the city, and the other way around – it would make the city accessible to the people who lived there.”

Open this photo in gallery The past decade’s transformation in western Amsterdam has been remarkable: Immigrant-run shops and pedestrians now thrive in areas that were once cement deserts. Isabel Nabuurs

Open this photo in gallery Slotervaart now enjoys greater density, with dead spaces filled by social, rental and condominium housing in varied scales and styles. Isabel Nabuurs

I first visited this project more than 10 years ago, when the Netherlands was still reeling from a 2004 terrorist slaying committed by an ethnically Moroccan Dutch man who grew up in one of the district’s characteristic low-rise apartment buildings. Amsterdam’s mayor (who was also targeted by the attacker) became persuaded that a big part of the radicalization problem was the physical design of the entire neighbourhood, whose empty, grassy spaces and isolated apartment clusters (along with mediocre schools) had bred immobility, alienation, economic disconnection and, sometimes, extremism.

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When I spent a few days in the district recently, I was shocked by its transformation – streets and squares that had previously been cement deserts with few people and no commerce had turned into thriving places with immigrant-run shops and crowds of young pedestrians; bleak grassy expanses had been filled with tight-knit houses, shops and well-used parks; the ribbon of elevated freeways and train tracks that had isolated the entire quarter from the main city was now a dense and lively neighbourhood with hundreds of new apartments in elegant buildings.

“Before, it was a place where people wanted to get out of – you had radicalization, you had crime, there were limited opportunities for young people,” says Ahmed Marcouch, a Moroccan-born Dutch politician who served as a police officer and then as a city councillor and member of parliament for this district. “Now, people want to come here, and, importantly, people are taking pride in their community and investing in it.”

Some of the interventions respected the postwar apartment buildings and simply filled in the scary spaces with new features – or added housing and shops to give the residents a sense of ownership. The architect Paul de Ruiter filled a former public-housing courtyard with a chic, wood-clad “urban block” containing a community school, a child-care centre, 71 units of housing and a small park.

Open this photo in gallery Paul de Ruiter’s ‘urban block’ development in Amsterdam. Paul de Ruiter

Others are more dramatic. Dutch architects Köther Salman Koedijk got rid of the curvy streets and grassy verges completely and built a straight street lined with a set of eight- to 11-storey apartment buildings, with space for shops and services at the sidewalk level, in a layout that resembles Toronto’s Spadina Avenue. It contains perhaps four times the population density of the old park-city neighbourhood – and a sense of life and busyness that feels more urban and less “lost.”

That was a big part of the overall project: to fill in many of the empty spaces with housing, eventually more than doubling the district’s population. At first, 70 per cent of the new apartments were built for purchase – both a deliberate attempt to attract a middle class and a way to finance the larger project through sale of units. In this respect, it resembled Toronto’s rehabilitation of the Regent Park public-housing project, in which architect Peter Clewes and his firm architectsAlliance doubled its population density by filling dead spaces with both social, rental and condominium apartments in a range of scales and styles.

In western Amsterdam, this approach had an unexpected effect: While the city had expected the condominium apartments to attract a much-needed middle class, they were surprised to find that much of that middle class came from within – Turkish immigrants and their children who’d done well for themselves bought up the condos in their own neighbourhood rather than moving out. It is no longer a district people want to escape.

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Open this photo in gallery Stairs lead down from Parkway Forest Drive to Sheppard Ave. East in Toronto’s Parkway Forest neighbourhood. The dense cluster of tall apartment buildings and condominiums has begun to open up, with a new community centre and pathways to the nearby subway station. Fred Lum/The Globe and Mail

Toronto

The problem of empty space is especially acute in Canada, where decades-old suburban apartment districts have become the pre-eminent sites of immigrant settlement and integration during the last decade. Indeed, the suburban private-rental “slab farm” apartment district may be Canada’s unique contribution to housing; there are 2,000 such concrete towers in the Greater Toronto Area alone, most of them marked by empty voids and sprawling parking lots separating buildings from one another and from the wider world and its economy.

Yet, Canadian cities seem to lag at least a decade behind many of their European counterparts in recognizing the social, economic and ecological problems posed by empty spaces. Some suburban cities, notably Surrey, B.C., and Mississauga have confronted this problem as part of their efforts to build more dense “downtown” districts. And the construction of new rapid-transit lines in Vancouver, Montreal and the northern and western suburbs of Toronto has enabled higher-density development along those lines.

Canada’s most ambitious confrontation with empty spaces is the set of incentives Toronto has developed to encourage the owners of those slab apartment buildings to turn the parking lots and empty lawns between the buildings into hives of commerce, learning, community activity and, potentially, more housing. Among those incentives is the city’s “Residential Apartment Commercial” (RAC) zoning category, which became law in 2016, and allows building owners to create restaurants, shopping and eating districts, galleries, child-care centres and other services in the spaces beneath their buildings without applying for approval.

Graeme Stewart, the architect (with ERA Architects) who developed and promoted these “Tower Neighbourhood Renewal” policies, says that these incentives have been slow to be taken up by owners. “What we’ve found is that while there’s huge opportunity in all the open space around these buildings, there isn’t clarity on what’s the best way to do it. A lot of this housing belongs to existing neighbourhoods, so bringing change in is political and complicated.”

But a set of new developments this year, including more than $6-billion in funding for building rehabilitation (including in private-rental buildings) in the federal government’s housing strategy, may kick-start a spurt of construction in the valleys between towers.

Canadian cities are beginning to learn the lesson of Mexico City – that it’s the small things that count in transforming the dead zones. “The challenge is going from these micro-interventions – which are beginning to happen – to bring in macro-investments, like new housing, like mass transit,” Mr. Stewart says. “I think we’re at the beginning of a larger conversation about how we open up these spaces.”

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But Canada also needs to learn the lesson of Amsterdam – that the empty spaces can house many more people and allow greener, more enjoyable lives, if we think big.