The Density Tipping Point

Gas prices are on everyone’s mind these days. Supply shocks from global conflict have pushed fuel costs to levels that are forcing people to rethink how they get around, and prompting planners to revisit a long-standing question: when does a neighbourhood become dense enough to give people a real choice to rely on cars less?

The answer, it turns out, has a measurable threshold. Once residential density crosses a critical point, car dependency drops off sharply.

Graph showing the relationship between density and car dependency. The Y-axes represent the probability of using a car as the main mode. (Cao, et al., 2022)

According to a recent study that analyzed travel data from 82 cities and towns in the Puget Sound Region, Washington State, neighbourhoods began to show reduced car dependence at around 70 housing units per hectare. That region is much like many in Canada, with a dense core city and surrounding mid‑sized, car‑dependent communities working to balance intensification, transit, and climate action.

At this level, car dependence begins to decline, transit becomes financially viable, local retail can sustain consistent foot traffic, and investments in cycling and pedestrian infrastructure start to pay off. Below that threshold, none of these systems work, not because residents don't want them, but because the density simply can't support them.

A mid-density, low-rise neighbourhood supported active transportation.

A comparison of three Canadian neighbourhoods, Rosemont La Petite-Patrie in Montréal, Centennial in Oshawa, and Erin Woods in Calgary, reveals a similar pattern in residential density and walkability and reinforces the idea that neighbourhoods generally need to exceed 70 units per hectare to function as truly walkable places.

This image compares residential density, built form, and Walk Scores® in three Canadian neighbourhoods.

The streetscape of these low-density, Canadian neighbourhoods typically look like the image below. These areas were designed around the automobile, characterized by post-war lots, detached homes, and densities hovering around 10-15 dwellings per hectare. That design made sense in the 1960s, but today these neighbourhoods are a huge fiscal drain on their municipalities, in order to maintain infrastructure like pipes, roads, and parks. The tax base is spread thin, and many have infrastructure that’s in deep need of repair. 

Typical Canadian post-war neighbourhood

Neighbourhoods like this hold enormous untapped potential for infill. If we tweak the rules to make it easier to build compact, two or three‑storey buildings with four to twelve units, these areas could more than double the number of people they can house over the next 20 years.

Examples of low-rise, multi-unit buildings up to three-storeys in height.

A handful of forward-thinking municipalities have moved to upzone their low-density neighbourhoods to do just this. However, they didn’t reverse-engineer their regulations, taking into account market response, so the infill housing supply outcomes vary and are sometimes disappointing. In some municipalities, these upzonings have been contentious. In Calgary, broad upzoning across entire residential zones triggered significant backlash, and regulations have been repealed. In Edmonton, pushback has resulted in modifications that cripple some development opportunities.

Recent headlines about stalled or repealed infill upzoning regulation changes.

Design quality was another hot‑button issue. Some infill buildings, like the ones below, had little consideration for the human scale and their impact on the surrounding neighbourhood. Lively streets depend on seeing other people and signs of life—think large windows, green space, gardens, and porches or balconies where people sit and watch the world go by. Yet these examples are marked by blank façades, small windows, and small or absent balconies and porches.

New infill designs that lack street-enhancing animated facade features.

In other cases, upzoned lots sit vacant because developers simply can’t make the business model work. 

These are not impossible problems. They are, however, problems that require deliberate regulatory design, not just a change in permitted densities. 

It's time to take a more targeted approach to overcoming these challenges. Rather than relying on blanket upzoning, municipalities should focus zoning changes on areas best suited for infill. This allows them to preserve the broader zoning framework while minimizing widespread community opposition. To ensure new development complements low-rise neighbourhood character and contributes positively to the public realm, facade zoning is essential. When applied strategically, targeted zoning can be reverse-engineered to create the conditions needed for viable business models and to meaningfully accelerate low-rise infill development.

Examples of low-rise, multi-unit builds from the BuildingIN catalogue. 

The good news is most municipalities are closer than they realize to that density tipping point where neighbourhoods can begin to function as truly walkable places. Reaching that threshold doesn't require a sweeping rewrite of zoning bylaws or years of contentious public consultation, but rather a more precise and deliberate approach to infill housing. 

We work with municipalities to determine how much infill housing can realistically be added in existing neighbourhoods, then reverse‑engineer the rules so that those homes actually get built—applying a holistic lens that integrates industry, architecture, and planning.

If you’d like to see how it could work in your community, contact Rosaline Hill at info@buildingin.ca or call 613-262-5480 to begin the conversation or book a demo here. 

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Rosaline Hill is a principal architect, planner, and development consultant with over 25 years dedicated to designing homes and communities that work. She founded RJH Architecture + Planning, Walkable Ottawa, Ottawa Cohousing, and BuildingIN, each building on her passion for smarter, more sustainable housing solutions.

With support from her CMHC Housing Supply Challenge winnings, Rosaline launched BuildingIN, an infill consulting practice advancing a data-driven approach that unifies Canada’s fragmented housing market for low-rise, multi-unit infill. Her proven methodology has guided municipalities, large and small, through transformative change. Today, she partners with governments across the country, empowering changemakers to unlock scalable, affordable housing solutions where they are needed most.

Sources:

Cao, J., Jin, T., Shou, T., Cheng, L., Liu, Z., & Witlox, F. (2023). Investigating the nonlinear relationship between car dependency and the built environment. Urban Planning, 8(2), 1–15. https://www.cogitatiopress.com/urbanplanning/article/view/6293/3160

Statistics Canada. (2025, August 26). Canada’s dwelling stock and home ownership, 2024. https://www150.statcan.gc.ca/n1/daily-quotidien/250826/dq250826a-eng.htm

Statistics Canada. (2024, August 26). Housing starts, 2024 (Table 002). https://www150.statcan.gc.ca/n1/daily-quotidien/240826/t002a-eng.htm