By Sara Rahgozar, M.Arch, OAA, Quadrant Architects
If you own a house in Toronto, you can now put up to four units on your lot, a duplex, triplex, or fourplex, without a rezoning, a hearing, or a public meeting. City Council made this legal city-wide on May 10, 2023. It is one of the biggest changes to what a homeowner can do with their property in decades.
But there is a catch worth understanding before you get excited or spend money on drawings. “Allowed” comes with a set of limits on the size and shape of the fourplex you can build. Stay inside those limits and your project goes straight to a building permit. Break even one of them and you are sent to a City committee for a variance, which can add many months and tens of thousands of dollars, with no guarantee you win. This guide explains the limits in plain terms so you know what you can build and what would force you into a variance.
It means you do not have to ask the City’s permission to build a fourplex. The zoning already allows it. You submit a building permit application showing your design follows the rules, and if it does, the City has to approve it.
That is a big deal, because the alternative is slow and expensive. If your design needs a variance, the approval can take 12 to 24 months and cost $20,000 to $50,000 or more in planning and legal fees, and it can still be refused at the end. So the entire game is designing a fourplex that fits the rules from the start, so you never have to go through that. Everything below is about staying on the safe side of that line.
There are really only four things that limit the size and shape of your fourplex: how tall it can be, how much of the lot it can cover, how far it has to sit from the property lines, and how deep it can go. There used to be a fifth limit, on total floor area, and the fact that it no longer applies is what makes fourplexes work. Here is each one at a glance, before we go through them in turn.
| Limit | Typical range |
|---|---|
| Height | 10 to 12 metres in most zones (about 3 storeys); a multiplex can reach 10 metres even where the map shows less |
| Lot coverage | 30 to 50 percent of the lot, depending on the zone |
| Front setback | 4.5 to 7.5 metres, often set by the neighbours’ average (prevailing setback) |
| Side setbacks | 0.45 to 1.2 metres, depending on lot width and building height |
| Rear setback | Generally 7.5 metres |
| Building depth | Up to 19 metres, front wall to back wall, on a lot with room for it |
| Floor space index (FSI) | Does not apply to multiplexes, unless a Chapter 900 site-specific exception imposes one |
Every number here shifts with your specific zone and any site-specific exception, so treat the table as orientation and confirm your own figures. The sections below explain what each one means in practice.
Most Toronto residential lots allow a building 10 to 12 metres tall, which is about three storeys. Even where the map shows a lower limit, a fourplex is allowed to reach 10 metres. Height is measured from the ground up to the peak of the roof, and on a sloped lot exactly where the City measures the ground from can gain or cost you usable height, which is worth getting right early.
You are allowed to cover a set percentage of your lot with the building, usually somewhere between 30 and 50 percent depending on where you are. This is a hard limit. Even if four units would physically fit, you cannot cover more of the lot than the percentage allows. This is one of the most common reasons a design has to shrink or gets sent to the committee, so it is worth checking your number before you fall in love with a big footprint.
The building has to keep a minimum distance from each edge of your lot, called a setback. The front setback is often not a fixed number: in many neighbourhoods your front wall has to line up with the average of the houses on either side, so what your neighbours did partly decides where your house sits. The side gaps are small, often between about half a metre and just over a metre, but on a narrow lot they eat up a real share of your width. The rear setback is usually 7.5 metres, which shortens how deep you can build on a shallow lot. These distances are the same as for any house in your area; the fourplex rules did not change them.
A fourplex can be up to 19 metres deep, front wall to back wall, on a lot with room for it. This works together with the rear setback. On a lot that is 30 metres deep, once you leave 7.5 metres at the back and about 6 at the front, you have around 16.5 metres to build in. On a deeper lot you can use the full 19.
On a normal building project, the limit that usually holds you back is a cap on total floor area relative to lot size. For fourplexes, that cap does not apply. This is the single reason you can fit four units into roughly the same building size as a large single house. The only thing to watch is a site-specific exception (the City calls it Chapter 900) that can put a floor-area cap back on one particular property, so it is worth checking whether yours carries one.
The rules technically allow a fourplex on a lot as narrow as 6 metres, about 20 feet. But allowed and practical are different. On a 6-metre lot, once you subtract the side gaps you are left with roughly 4.2 metres of building width, which is tight for one unit, never mind four.
Width is what decides how your units are arranged. On a narrow lot, there is not enough room to place units beside each other, so they have to stack on top of one another, one per floor. On a wider lot, you have the option of placing units side by side as well as stacking them, which opens up more layout choices and can make for larger, better-lit units. The permission is the same everywhere, a 25-foot lot has the same right to a fourplex as a 50-foot lot, but the two will produce very different buildings. Knowing which yours can support is the first practical question to answer.
No. Since February 2022, Toronto requires no parking at all for a duplex, triplex, or fourplex, anywhere in the city. For most owners this is a gift: no digging for underground spaces, no driveway eating your frontage, more of the lot free to build on, and lower construction costs. You can still add parking if it suits your lot, but you do not have to. You may need to provide a couple of bicycle parking spots depending on the project, which is easy to accommodate.
A few arrangements reliably produce a fourplex that fits the rules:
Whatever the layout, each unit needs its own kitchen, bathroom, living space, and bedroom; the walls and floors between units have to meet fire-separation rules, which are not optional; stacking kitchens and bathrooms above each other saves real money on plumbing; and every unit needs proper natural light, which is the main challenge for basement units.
Both routes are open. Converting your existing house into four units is often faster and can cost less, but you are working with what is already there, and older Toronto homes usually need structural work, waterproofing, new plumbing and electrical, insulation, fire separation, and layout changes. Building new means removing the existing house and putting up a purpose-built fourplex, which gives you the best layouts and full code compliance but costs more and takes longer.
One money point that favours converting: the City does not charge development charges on a triplex or fourplex conversion, which can save a significant sum compared with a new build. The full cost picture, construction budgets, development charges, and financing, is covered in our separate guide to multiplex costs.
Anything that breaks one of the limits above, too tall, too much lot coverage, too close to a property line, too deep, or a site-specific restriction, means you need a minor variance before you can get a permit. That process involves fees, notifying your neighbours, a public hearing, and a decision that might approve, approve with conditions, or refuse you, with the chance of an appeal after. Figure on 3 to 6 months if nobody appeals, and $10,000 to $30,000 or more in fees and consultants.
Avoiding that is the best thing you can do for your budget and your timeline, and it comes down to designing your fourplex within the limits from the start. That is exactly what a good architect is for, and it is the core of what we do as a multiplex architect. Get the design right on the first try and your fourplex goes straight to permit.
Sara Rahgozar, M.Arch, OAA, Quadrant Architects. 416-357-5713 · sara@quadrantarchitects.com
Current as of August 2026. Zoning rules change. Verify the rules for your specific address through the City of Toronto’s Interactive Zoning By-law Map or Toronto Building Customer Service before making design or investment decisions.