What Can You Build on Your Toronto Lot? A Guide to Multiplexes

Toronto has changed the rules on what many homeowners can build. Lots that were once limited to a single detached house can now, in many cases, accommodate several homes under one roof. If you own a property in Toronto or elsewhere in the GTA, understanding the basics of multiplex development is a good first step before you talk to designers, lenders or builders.

This guide explains what a multiplex is, what has changed, what typically determines whether a project is feasible, and how a project usually moves from idea to construction. It is general information only. Zoning, building code and municipal requirements change and are site-specific, so every property needs its own review.

What is a multiplex?

A multiplex is a residential building that contains more than one self-contained dwelling unit. Common forms include:

• Duplex – two units, often stacked one above the other or side by side.
• Triplex – three units.
• Fourplex – four units, frequently arranged over three storeys with a lower level.
• Larger multiplexes – five or six units, which may be possible in certain areas where local zoning allows them.

A multiplex can be a new building that replaces an existing house, or an existing house that is converted and expanded to add units. Each approach has different cost, design and approval implications.

What has changed in Toronto?

In 2023, Toronto City Council amended the zoning by-law to permit multiplexes of up to four units in residential neighbourhoods across the city, subject to the zoning standards that apply to each lot. The City has continued to review its housing permissions since then, including permissions for larger multiplexes in parts of the city. At the provincial level, Ontario legislation passed in 2022 generally allows up to three residential units on many serviced residential lots.

These changes create opportunities, but they do not mean every lot can accommodate a multiplex. Built-form rules such as height, setbacks, building depth, lot coverage and landscaping still apply, along with the Ontario Building Code, fire safety and servicing requirements. Always confirm the current rules with the City of Toronto or your municipality, or with a qualified planning professional, before making decisions.

Rules differ between Toronto and other GTA municipalities, and they continue to evolve. Treat any general guide — including this one — as a starting point, not a final answer for your property.

What determines whether your lot can support a multiplex?

A feasibility review looks at the property as a whole. Typical considerations include:

• Zoning and permitted building envelope – the height, depth, setbacks and floor area the by-law allows on your specific lot.
• Lot size and shape – frontage, depth and any irregularities influence layout and unit count.
• Servicing capacity – water, sanitary and storm connections may need to be assessed and upgraded for additional units.
• Building code and fire separation – multi-unit buildings require fire separations, exits, sound control and other life-safety measures.
• Trees – protected trees on or near the property can affect where and how you can build.
• Parking and access – requirements vary, and access for emergency services must be considered.
• Existing structure – for conversions, the condition of the foundation, framing and systems matters a great deal.
• Budget and financing – construction costs, consultant fees, permits, municipal charges and financing terms all shape what makes sense.

New build or conversion?

Converting an existing house can sometimes reuse part of the structure, but older homes may need significant upgrades to meet current code for fire separation, egress, insulation and mechanical systems. A new build offers more design freedom and can be planned around today’s requirements from the start, but involves demolition and a larger overall scope. The right choice depends on the property, your goals and your budget, which is why it is worth comparing both early.

How a multiplex project typically unfolds

1. Initial consultation – discuss the property, goals, budget and timeline.
2. Feasibility review – zoning, servicing, site constraints and a high-level look at what may be possible.
3. Design – an architect or designer develops plans, often with structural, mechanical and energy consultants.
4. Permits and approvals – building permit applications and, where needed, other approvals such as a minor variance.
5. Budgeting and scheduling – detailed pricing, procurement and construction planning.
6. Construction – site work, foundations, framing, services, finishes and inspections.
7. Completion – final inspections, occupancy and handover.

Timelines vary widely depending on the property, design complexity, approval requirements and market conditions, so it is wise to plan conservatively.

Questions to ask before you start

• What are my goals – rental income, multigenerational living, sale, or a combination?
• Am I prepared for the cost and time of design and approvals before construction begins?
• How will I finance the project, and have I spoken with a lender who understands multi-unit construction?
• Who will coordinate the architect, engineers, permits and trades?

Next steps

If you are wondering what might be possible on your Toronto or GTA property, a conversation about your lot, goals and budget is a practical place to begin. BRK Developments can help you think through the options and coordinate the professionals your project needs. Any assessment depends on the specific property and on current municipal requirements.

This article is general information only and is not legal, financial, tax or planning advice. Rules and programs change and vary by municipality — confirm current requirements with the City, CMHC, your lender or qualified advisers.