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Will fourplexes be actually feasible in Toronto?

Last week I wrote about Toronto’s plan to make fourplexes as-of-right across the city, but also why this form of missing middle housing shouldn’t have a maximum floor space index.

Today, let’s look at the numbers in a bit more detail.

If you look at a zoning map of Toronto, you’ll see that many neighborhoods across the city have a maximum floor space index (FSI) of 0.6. What this means is that if you have a piece of land like this:

  • Lot width: 20′
  • Lot depth: 115′
  • Site area: 2,300 sf

Your total allowable gross floor area would be 1,380 square feet (0.6 x 2,300 sf).

If you build a laneway suite in this city, that won’t count towards your total allowable GFA (otherwise they’d be very challenging/impossible to build). But if you want to build something like a triplex or a fourplex, it counts.

The one important caveat is that if you’re building a residential building — that isn’t an apartment building with 5 or more homes — you can deduct the floor area of the basement:

This, of course, helps the situation. But it doesn’t solve all of our problems.

If you assume that the basement can be one home, that still only leaves 1,380 square feet for the other three, technically permissible, homes. This equals: 3 homes x 460 square feet.

Another option would be 2 homes x 690 square feet. But still, we’re not exactly making it easy to deliver more “family-sized homes” in the city.

And herein lies one of the problems (plural, because there are others). We can say that fourplexes are allowed across the city, but it may not actually be technically feasible or practical to build them.

Note: I am not a planner. If you are, leave a comment below.


  1. afinetheorem

    The FSI issue in Toronto is totally bonkers. Essentially all of downtown is non-conforming as built, let alone with any increase in density. As the OAA noted in response to the 2012 bylaw reform, Toronto’s planners operate under the default that everything should go to committee, which is why nothing can be build except by developers who have the knowledge and connections to be able to predict the vagaries of committee decisions, and the ability to sit on land for months without developing it while the city does whatever they do (I know this by current personal experience!). Indeed, the OAA in 2011 explicitly asked the city just to drop the GFA requirement altogether, since by definition height and setback requirements completely determine the exterior massing. When people say “what happened to the nice Victorian roofs in Toronto”, blame the government – the GFA rules, and how attic space is counted, is the reason!

    So, so frustrating even if we didn’t have a housing crisis. Even worse now how much housing we are letting sit fallow for no good reason.

    Liked by 1 person

  2. Joseph Hill

    Are you saying the home owner could deduct the basement GFA therefore adding and extra lets say 500sqft onto the allowable GFA for the rest of the house?


  3. Brandon, I am not a planner but have worked on the development side. From my understanding, Basements do currently count towards FSI for 3 units and above. So technically only duplexes and below are allowed to exclude Basements from FSI calculation. I believe EHON will change that.


    • My understanding is that the basement GFA counts if it’s an Apartment Building, which is defined as follows:

      Apartment Building means a building that has five or more dwelling units, with at least one dwelling unit entirely or partially above another, and each dwelling unit has a separate entrance directly from outside or through a common inside area. A building that was originally constructed as a detached house, semi-detached house or townhouse and has one or more secondary suites is not an apartment building.


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