Duplex vs Triplex vs Fourplex: Which Multiplex Should You Build in Toronto?

Thanks to Ontario's Bill 23 and Toronto's updated zoning bylaws, most residential lots in the city can now support up to four units as-of-right — no rezoning required. That means if you own a suitable lot, you have a choice: build a duplex, a triplex, or a fourplex. Each option comes with different costs, different income potential, and different design considerations. Understanding these differences is essential before you commit to a project.

Let us start with the numbers. A duplex in Toronto — two self-contained units, typically stacked — ranges from $700,000 to $1.2 million in total construction cost, not including land. A triplex runs $1 million to $1.8 million. A fourplex, the maximum allowed under current as-of-right provisions, typically costs $1.3 million to $2.5 million. These ranges reflect mid-range to high-quality finishes and full compliance with the Ontario Building Code for multi-unit residential construction.

Rental income scales accordingly but not linearly. A well-located duplex in Toronto can generate $4,000 to $6,500 per month in combined rental income from its two units. A triplex generates $6,000 to $9,500. A fourplex can bring in $8,000 to $13,000 or more, depending on unit sizes, finishes, and neighborhood. The incremental cost of adding a third or fourth unit is lower than the first two — you are already paying for the foundation, the roof, and the core building systems — so the return per dollar invested generally improves as you add units.

From a design perspective, duplexes offer the most flexibility. With only two units, you have room for generous floor plans — two- or three-bedroom units with full-sized kitchens, in-unit laundry, and private outdoor space. Duplexes also integrate most naturally into existing streetscapes, which matters in neighborhoods where context-sensitive design is valued. Many of our duplex projects are designed to read as single-family homes from the street, preserving the character of the block while doubling the housing.

Triplexes introduce more complexity. Three units need to share vertical circulation, which usually means a common stairwell and corridor on each floor. Unit sizes are typically smaller — one-bedroom and two-bedroom layouts are most common — and the building code requirements for fire separation, sound transmission, and means of egress become more demanding. That said, the economics of triplexes are compelling: you get 50 percent more rental income than a duplex for roughly 30 to 40 percent more construction cost.

Fourplexes maximize the revenue potential of a lot but require the most careful design. Four units on a standard Toronto lot (typically 25 to 40 feet of frontage) means smaller individual units, more complex mechanical systems, and the most rigorous code requirements. Parking can be a challenge — Toronto requires parking for multiplex units in most zones, though some areas now have reduced minimums. At Metrohomes, we have found that successful fourplex design comes down to efficient floor plans and creative use of vertical space. The projects that work best are on lots with 30 feet or more of frontage and good laneway or rear access for parking.

The zoning requirements differ by configuration. All three types are now permitted as-of-right on most residential lots in Toronto, but the building must still comply with height limits, setback requirements, and lot coverage maximums. A duplex fits comfortably on most lots. A triplex may require variance relief on narrower lots for side yard setbacks. A fourplex on a tight lot might push up against height limits or lot coverage — a feasibility study early in the process identifies these constraints before you invest in full architectural drawings.

Financing also varies by project size. Lenders evaluate multiplex projects based on projected rental income and completed value. Larger projects with more units generally qualify for better loan-to-value ratios because the income stream is more diversified. A fourplex with four tenants is a more stable income source than a duplex with two — if one unit is vacant, you still have three paying tenants covering the mortgage. Most of our clients finance multiplex construction through a combination of existing equity and construction loans, and we work closely with their lenders to provide the documentation needed for approvals.

Timeline is another consideration. A duplex from initial design to occupancy typically takes 12 to 16 months. A triplex runs 14 to 18 months. A fourplex can take 16 to 22 months, depending on site conditions and permitting timelines. The design and permitting phase is similar across all three — roughly three to four months — but construction duration increases with building size and complexity.

So which should you build? The answer depends on three things: your lot, your budget, and your goals. If you have a standard 25-foot lot and want to keep the project manageable, a duplex is often the best fit. If you have a wider lot and want to maximize income, a triplex or fourplex will deliver better returns. If you are looking at this as a long-term investment — hold the property, collect rent, build equity — a fourplex offers the strongest cash flow and the most favorable financing terms.

Our Property Assessment can help you evaluate your specific property. It analyzes your lot dimensions, zoning, and neighborhood to give you a preliminary assessment of what is buildable — whether that is a duplex, triplex, fourplex, or even a garden suite as a starting point.

At Metrohomes, we have designed and built multiplexes of every configuration across Toronto since the zoning changes took effect. Our investment consulting service includes detailed pro forma analysis so you can compare the financial performance of each option on your specific lot before committing. The right choice is the one where the numbers work and the design fits the neighborhood — and we help you find that intersection.