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The case for density transition zones (and why people will probably hate them)

Toronto is known for its tall buildings and its contrasting low-rise neighborhoods. More recently, we have seen a proliferation of mid-rise buildings along the city’s “Avenues.” This is despite the many challenges and costs associated with this building typology.

But I think it’s pretty clear that a further evolution is also underway. Laneway housing, which is now permitted “as-of-right,” is in the early stages of being adopted and built out all across the city. And eventually I think we’ll see many of Toronto’s laneways evolve into fully fledged residential streets; perhaps not all that dissimilar from what you might find in compact cities like Tokyo.

This is very exciting to me and I think of it as the city gaining a third hierarchy of residential streets. We’d have our major arteries and avenues. We’d have our residential side streets. And then we’d have our compact laneways. Dare I say that maybe some of these laneways could even house non-residential uses such as small-scale offices.

But along with this shift, I think it’s time we look at another infill opportunity — something that planners Blair Scorgie and Sean Hertel are calling “density transition zones.” What these zones hope to be is a new middle transition zone between low-rise neighborhoods (where laneway suites are already permitted) and mid-rise avenues. A place where “missing middle” type housing might be built in close proximity to major streets and existing transit. Let’s call it a 100-200m zone that sits right behind our avenues.

In my mind this is immediately beneficial for two reasons. The first is obvious. It could be a place for frictionless missing middle housing. Housing that’s more dense than a single family home + laneway suite, but less dense than a typical mid-rise building.

The second immediate benefit is that this transition zone could be used to help improve the overall feasibility of mid-rise avenue development. The reality is that there are many blocks along Toronto’s avenues where the lot depths are simply too shallow for proper mid-rise buildings. Density transition zones could help with this, which would be not that dissimilar from how “Enhancement Zones” were intended to work (they were never approved).

If this were to happen, I think there would also be a strong case for softening some of the “requirements” in the mid-rise design guidelines. Requirements like the 45 degree angular plane that new buildings generally need to conform to. All of this would only help the overall feasibility of more European-scaled developments along Toronto’s avenues and, in my opinion, that would be a great thing.

But for the same reasons that Enhancement Zones were highly contentious, I would expect a lot of grouchy people and a lot of pushback on this idea. There will be concerns about encroaching on our single-family neighborhoods, and there will be the usual objections that come up with any new development (density, traffic, dog poo, etc.) But if we’re serious about building more missing middle housing, we are going to need to find ways to remove the barriers to entry. This scale of housing is simply too small to support a great deal of friction.

To learn more about how density transition zones might work, I would encourage you to check out the great site that Blair and Sean have put together, over here.

Image: Density Transition Zones


  1. Michael Spaziani

    I was part of the St. Clair West Avenue Study consultant team and conceived the idea of Enhancement Zones. My role was to pro-forma test typical sites using development massing studies. I fould that 5.0 FSI and 9 storeys was the threshold viability level for development. It only worked when the approval process is smooth and fast. Tall order. The enhancement zone concept was born out of the idea that 9 storeys on the north side brought increased shadow impacts on adjacent R properties. In return those properties were granted increased development rights as a kind of compensation. Properties on the south of St. Clair were given a density boost with a 60 degree angular plane relationship to adjacent R properties. It is very interesting to see that a nearly 10 year old concept is gaining traction once again. I have been applying this thinking in various LPAT challenges recently and find that it is difficult to get planners off the 45 degree angular plane even when impacts are less present. It is time to make Enhancement Zones a policy right.

    Liked by 1 person

    • Hi Michael,

      To confirm, the Transition Zones concept was in fact inspired, in part, by your important work on Enhancement Zones! We even reference it on the website. Let me know of you ever want to connect and discuss further. It would be my pleasure.




  2. doug

    Brandon I cannot imagine that you do not know this of the grandfather laneway homes

    What you may not know is that Martin Liefhebber, the architect, also produced drawings at the very beginning showing an entire laneway converted to such homes and thus becoming a new street and a safe safe place. His first idea was that each home would have the footprint of a garage so that there would not be a loss of open space, The idea was to also eliminate the car that used to be in the garage

    I cannot find images of the converted laneway but I believe, if you are interested ,you could still contact Martin through Breate Architects..the one n Toronto not the one in Australia


      • doug

        Up above Michael mentions a ten year old idea that is just coming to light. Martins early ideas I think would by now be a quarter century by now. I think there is some kind of theory that the longer an idea takes to come to fruition the better idea is

        I forgot that is thinking (I knew him) included the concept that all these homes would not need any municipal infrastructure so that any added density only added that..density but without infrastructure demands


  3. Pingback: More on Enhancement Zones — a follow-up to density transition zones |

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