Toronto Fourplexes: What You Can Actually Build

In May 2023 Toronto passed By-law 474-2023 and quietly ended the single-family-only era: multiplexes of up to four units became permitted as-of-right, city-wide, in every neighbourhood zone. "As-of-right" is the phrase that matters — it means you apply for a building permit and build. No rezoning application, no community meeting, no Committee of Adjustment unless your specific design asks for something extra.

What the by-law hands you

• Four units in one building, anywhere residential. Duplex, triplex, fourplex — permitted in every R, RD, RS, RT and RM zone in the city.
• 10.0 metres of height, city-wide, for multiplexes — and the storey caps painted on older zoning maps do not apply. That's what makes the standard three-storeys-plus-basement building work even where the map says "2 storeys."
• FSI (density) maximums do not apply to buildings of up to four units. The old 0.6-times-lot-area math that killed projects for decades is simply switched off for multiplexes.
• Deeper buildings on deep lots: the standard 17 m building depth stretches to 19 m where the lot is deep enough — meaningful on Toronto's long suburban parcels.
• $0 development charges currently apply to buildings of up to six units in Toronto — a five-to-six-figure saving that suburban municipalities don't match.

The three rules that still bind

1. Lot coverage. The multiplex by-law did NOT exempt coverage — the overlay on your lot (typically 33–35%) still caps your building footprint, and on most lots it's the real constraint that sizes the building. Footprint times four levels is your envelope; coverage sets the footprint.

2. Setbacks. Side yards (typically 0.9 m), front yard matching the street, rear yard — all still apply. On narrow lots, the side setbacks decide your building width, and whether a garden-suite fire path fits beside the house.

3. Site-specific exceptions. Thousands of Toronto lots carry a bracketed exception number in their zoning — an (x-something) — holding rules written for that street decades ago: bigger setbacks, floor-area caps, servicing quirks. Some help you, some hurt, and whether the multiplex by-law overrides a given exception is a genuine question for a zoning examiner. This is the single most common source of surprises — and why we pull the exception text on every site read before promising anyone anything.

Beyond four: the sixplex wards

In 2025 the city went further in nine wards — 4, 9, 10 through 14, 19 and 23 — where detached buildings can hold five or six units as-of-right, with a raised-basement height allowance of 10.5 m. Outside those wards, four in the building plus a garden suite is the ceiling; inside them, six plus a suite. Ward boundaries don't care what your house looks like — they're the first thing to check about any address.

What still kills projects

As-of-right zoning doesn't repeal physics or paperwork: protected trees (anything ≥30 cm across needs an arborist and permits), ravine and floodplain overlays, rail-corridor adjacency, servicing capacity, and tenants in place (whose rights under Ontario law must be handled properly and humanely) can each reshape or sink a scheme. The by-law opened the door; the site read tells you what's actually behind it.

Zoning summary current to September 2026; by-laws and their interpretation are determined by the City of Toronto. Not legal advice — every lot needs its own zoning review.