Using Toronto's Existing Housing Stock to Help Solve the Housing Crisis
Unlock Toronto’s "hidden housing inventory" by leveraging new as-of-right rules to turn large existing homes into profitable multi-unit housing.
How Using Toronto’s Existing Housing Stock Could Help Solve the Housing Crisis
Toronto is in the middle of a housing crisis, and we may be overlooking one of our most valuable resources: the houses we already have. Toronto’s condo market may be crashing, but the houses located in our older neighbourhoods have remained largely unchanged for decades and may provide an underused and overlooked resource to support the city’s growth.
In May 2023, the city significantly changed development rules: the Toronto City Council adopted Official Plan Amendment 601 and Zoning Bylaw Amendment 569-2013. Now, developers can build up to four units on almost any residential lot "as-of-right", and in some wards you can even go up to six units, all with the goal of increasing ‘missing middle’ housing stock.
However, increasing density does not have to mean tearing neighborhoods down and starting over. Adaptive reuse through internal conversion can offer a cheaper, faster, and greener, path forward. By dividing large existing homes into multiplexes that comply with these new guidelines, we can deliver the housing Toronto needs right now without the high costs and environmental impact of traditional new construction.
Changing the Math
The biggest hurdle to new housing today is the cost of construction. Building a custom home from the ground up in Toronto can cost between $350 and $900 per square foot (Marvel Homes). When you add in the time it takes to get permits, many small-scale projects simply don't make financial sense.
Internal conversion changes the math. By using the "sunk costs" of an existing building, such as its foundation, exterior walls, and roof, you can save a massive amount of money. A basement conversion to a legal suite typically costs between $100,000 and $300,000 (BVM Contracting). Even a full "gut" renovation of an older home usually costs around $450 to $550 per square foot, which, while still significant, is often a much more predictable investment than a custom new build (BVM Contracting).
The real difference-maker is the timeline. A new build can take nearly three years from start to finish (Marvel Homes) due to the extensive permitting processes, during which the developer must pause interest on land loans and construction financing. On the other hand, a conversion project can be completed in just 5 to 8 months (BVM Contracting). The City of Toronto even fast-tracks permits for secondary suites, often approving them in just two months. For a city that needs housing now, this speed is a game-changer.
Toronto’s Goals for Sustainability
We also have to talk about the environment. Most of Toronto’s climate goals focus on "operational carbon", the energy used to heat and cool a building. But "embodied carbon", the emissions created by making concrete, steel, and wood, is just as important.
Demolishing a house to build a new one is a carbon disaster. From a City of Toronto report, a new build can produce about 80 tons of CO2 equivalent. An internal conversion produces only about 8 tons (City of Toronto), proving to be a 90% reduction. By reusing the foundation and the brick walls, we keep that carbon "sunk" in the ground instead of releasing it into the atmosphere.
Toronto’s Hidden Housing Inventory
Not to mention, Toronto is full of "hidden inventory"—large buildings potentially ready for conversion, that currently house only one family but have the space for three or four.
ERA Architects has pointed out that converting existing housing stock into "missing middle" housing isn't a new idea for Toronto. Our historic neighbourhoods like the Annex, Cabbagetown, and Parkdale are full of large Victorian and Edwardian homes that were converted into apartments decades ago (see some examples of this in the images below). These neighbourhoods make up Toronto’s heritage conservation districts while also accounting for a great percentage of the city’s low-scale residential typologies. These buildings are perfect for reuse because they have high ceilings and solid structures that make it easier to meet modern fire and sound codes. What’s more is that this kind of housing stock can be found everywhere throughout Toronto’s historic neighbourhoods.
But the opportunity isn't just in historic homes. Toronto is also filled with thousands of "monster homes" (Toronto Star), the massive, detached houses built in the 1990s and 2000s in areas like North York and Etobicoke. While these homes are often criticized for their size, they are actually ideal "shells" for multiplexes. Many of them are already equipped with modern wiring, wide staircases, and high-ceiling basements, making them much easier to convert than a 100-year-old house.
An example of a multi-unit house conversion, this would have previously been one dwelling and more entrances were added and the floor program was redistributed into multiple dwellings. Image created by Felicity Xiao.
Purpose-built multiplexes (Duplexes, Triplexes and Fourplexes) could be converted even further by splitting levels. Image created by Felicity Xiao.
Historic walk-up apartment buildings are easily converted into multiple units. Image created by Felicity Xiao.
Finding the Best Sites: The Ratio.City Workflow
Taking advantage of Toronto’s hidden inventory requires a quick and efficient way to find the right properties. Ratio.City streamlines this process with our comprehensive and cohesive collection of data on Toronto’s heritage properties. Here is how you can use it to find your next multiplex conversion: I’m going to use the example of finding appropriate sites around Cabbagetown.
- Locate: Using Ratio.City’s Locate Mode, we can identify specific parcels with heritage registered sites to convert.
Ratio.City’s Locate mode allows users to find specifically zoned parcels. - We can then filter the Heritage Sites Category, we can further pinpoint a site’s specific by-law, zoning data, and heritage status. For historic conversions, the platform can help identify if a building is listed or designated, which will inform the final design strategy.
Ratio.City's Heritage Register Sites layer can tell you which sites are listed. - We can then filter on Toronto’s Heritage Conservation Districts layer. This will identify which sites are located in special designated areas protected under Ontario’s Heritage Act and the city’s by-laws.
Ratio.City’s Heritage Conservation Districts layer will help identify which sites are located in areas with special designations. - Additionally, we can filter for Land Use, to ensure that the properties being looked at are located within residential or mixed use areas.
Overlaying the Land Use Category layer will help identify which sites are more suitable for residential conversion.
Searching with all the layers overlayed yields four results within the bounds of the filters.
After searching with the applied filters, four potential sites were found that may be suitable for conversion.
Moving Forward
Converting Toronto’s existing housing stock isn't just a design trend; it's a financial and environmental necessity. By focusing on the "sustainability of subtraction," we can create a city that is denser and more diverse without losing the character of our neighbourhoods.
For homeowners and "citizen developers," the message is clear: the most profitable and sustainable house you can build might be the one you're already standing in.