Short answer: there is no single price per square foot for a Toronto multiplex, and anyone who gives you one without seeing the lot is guessing. What we can give you is the structure of the budget: hard construction costs, soft costs, City charges, and the rebates and financing that can change the math dramatically. Two of those (the HST rental rebate and CMHC’s MLI Select) only apply above certain unit counts, which is why a fourplex and a triplex on the same lot can have very different numbers.
All figures below are sourced from the City of Toronto, the Canada Revenue Agency, CMHC, Statistics Canada and the Altus Group 2026 Canadian Cost Guide. They are market benchmarks and program rules, not a quote. For the zoning side, see our companion guide to Toronto multiplex rules.
Why there is no single price per square foot
A multiplex budget is driven by a handful of decisions that vary from lot to lot:
- Conversion or new build. A conversion keeps the existing structure but inherits its problems: low basements, old wiring, failing drains, stairs that do not meet code for multi-unit use. A new build starts clean but pays for demolition, foundations and a full new structure.
- The lower level. Lowering a basement, underpinning or building a raised lower unit is often the single most expensive line in a conversion.
- Unit count. The jump from two units to three brings full fire and sound separations between units. The jump from three to four can unlock the HST rebate. The jump to five or more can unlock MLI Select financing.
- Servicing. A fourplex is expected to need a 400 A underground electrical service, and larger projects may need a transformer on the property. New water and sewer connections are common.
- Site conditions. Protected trees, tight side yards, shoring next to a neighbour’s foundation, and access for equipment on a narrow lot all add cost.
- Finish level and unit mix. Two-bedroom units rent better but cost more to build per unit than one-bedrooms.
Hard costs: what the benchmarks say
The most widely used independent benchmark is the Altus Group Canadian Cost Guide. For 2026, it puts wood-frame residential construction of up to six storeys in the Greater Toronto Area at $210 to $330 per square foot in hard costs, excluding land, soft costs and HST.
Treat that as a floor rather than a target. The guide’s benchmarks are built from larger developments that enjoy economies of scale. A three-storey multiplex on a 25-foot lot has the same fixed costs (excavation, foundations, a roof, a stair core, an electrical service, a sanitary connection) spread over far fewer square feet, and small infill sites are slower and more awkward to build on. Conversions vary even more, because the cost depends almost entirely on the condition of the existing house.
For scale, the City’s monitoring of the first 18 months of multiplex permits found an average unit size of about 106 m² (roughly 1,140 sq ft), with 65% of units having two or more bedrooms.
Soft costs: design, permits, surveys and engineering
Soft costs are everything that is not physical construction. On a multiplex they typically include:
- Design. Architectural drawings for a custom design, or the site-specific work needed to use the City’s free pre-approved fourplex and sixplex plans. Even with pre-approved plans, a qualified design professional must provide sealed letters covering the site: soil bearing, shoring, neighbouring footings, heating and cooling loads and sanitary connections.
- Surveys and engineering. A topographic survey, lot grading plan, structural engineering and, for conversions, an assessment of the existing structure.
- Building permit fees. Toronto’s 2026 fee schedule includes a residential unit fee of $56.33 per unit, on top of area-based fees for the work itself.
- Arborist reports and tree permits where protected trees (30 cm or more in diameter) are affected.
- Utility connections. Toronto Hydro service upgrades and new water and sewer connections.
- Committee of Adjustment application and professional fees, if your design needs a minor variance. Most multiplexes do not: only about 10% of the permits in the City’s detailed review did.
Development charges: mostly waived, with a cut pending
Development charges are one-time fees the City levies on new housing to pay for infrastructure. They used to be one of the biggest obstacles to multiplexes. Today:
- Units two through six are exempt in a residential development of up to six units, effective July 24, 2025. Before that, only units two to four were exempt.
- The first unit is not exempt, but if you are replacing a demolished house, a demolition credit usually offsets it. For reference, the City’s non-rental charge for a single or semi-detached house has been $137,846 since June 26, 2025. Confirm your project’s figure with the City.
- A reduction is coming, but is not in effect yet. Canada, Ontario and Toronto announced a program to cut residential development charges, and Council has amended the by-law. The City says more details will follow once the transfer payment agreement with the Province is received. Do not count on it until it is confirmed.
HST: the purpose-built rental rebate
This is the rule that most often decides between a triplex and a fourplex. The federal Purpose-Built Rental Housing rebate refunds the full 5% GST, or the federal part of the HST, on qualifying new rental buildings, and Ontario offers a matching rebate of its 8% portion. To qualify, according to the Canada Revenue Agency:
- the building must have at least four units, each with a private kitchen, bath and living area (or ten or more units);
- at least 90% of the units must be held for long-term residential rental;
- construction must have started after September 13, 2023 and before 2031, and be substantially completed before 2036.
Three exclusions matter for homeowners:
- Duplexes and triplexes do not qualify.
- Substantial renovations of existing buildings do not qualify. The rebate is for new construction, so most conversions are out.
- Living in one unit can disqualify a fourplex. The CRA’s own example: an owner who lives in one unit of a new fourplex and rents three has only 75% rented, below the 90% test, so the building is ineligible.
So the rebate generally fits a new-build fourplex or sixplex that is fully rented. If you plan to live in one unit, or you are converting an existing house, budget without it. Get tax advice before relying on it either way.
Financing: CMHC Refinance vs. MLI Select
Two CMHC programs matter, and which one applies depends on unit count.
| CMHC Refinance for secondary suites | CMHC MLI Select | |
|---|---|---|
| Units | Up to 4 | 5 or more |
| How much | Up to 90% of the as-improved value, which must be under $2 million | Up to 95% of cost for new construction, depending on points earned |
| Amortization | Up to 30 years | 40, 45 or 50 years at 50, 70 or 100 points |
| Key conditions | One unit owner-occupied (or occupied rent-free by family); no rentals under 90 days; approval before construction starts | At least 50 points from affordability, energy efficiency and accessibility commitments; minimum debt coverage ratio of 1.10 |
That five-unit threshold is why you will hear about the “4 + 1” strategy: a fourplex plus a garden or laneway suite on the same lot, which Toronto now permits together. Five units can open the door to MLI Select’s longer amortization, which can make the carrying costs work where a four-unit mortgage would not. It is not automatic. The points system involves real commitments, including affordable rents if you earn points that way, so model it with a mortgage professional who works with CMHC multi-unit insurance.
One more correction worth repeating: the $80,000 Canada Secondary Suite Loan announced in 2024 was cancelled in the 2025 federal budget and never launched. We covered the details in our guide to financing a basement suite in 2026.
Property tax
A building with up to six units stays in the residential property tax class, so you do not jump to the multi-residential rate. Expect your assessment to rise to reflect the added units, as it would with any major improvement.
What the rents support
Two credible reference points for Toronto rents in 2026:
- The City’s multiplex monitoring found an average multiplex rent of $2.93 per square foot per month. At the average unit size of about 1,140 sq ft, that is roughly $3,340 a month.
- Statistics Canada reported an average asking rent of $2,660 for a two-bedroom in Toronto in Q1 2026, down 1.1% from a year earlier.
Rents have softened from their peak, so build your numbers on today’s figures, not 2023’s. A simple illustration, using the Statistics Canada figure: a fourplex with four two-bedroom units at $2,660 would bring in about $10,640 a month, or $127,680 a year, before vacancy, maintenance, insurance and property tax. If you live in one unit, take one unit off that number and remember the HST rebate is likely off the table.
Also notice the gap the City found between multiplex and condo values: multiplex units resold for an average of about $562 per square foot, versus $969 for condos. Multiplexes in Toronto are mostly held as long-term rental buildings, not built to sell off unit by unit; registering one as a condominium is rare and expensive (the City cites costs of over $80,000). Plan around holding and renting, not selling units.
Duplex vs. fourplex vs. fourplex + garden suite
| Duplex | Triplex | Fourplex (new, all rental) | Fourplex + garden suite | |
|---|---|---|---|---|
| Building Code | Two-unit relaxations apply | Full multi-unit rules | Full multi-unit rules | Full multi-unit rules plus suite fire access |
| Development charges | Second unit exempt | Units 2-3 exempt | Units 2-4 exempt | Units 2-5 exempt |
| HST rental rebate | No | No | Possible | Possible |
| CMHC program | Refinance | Refinance | Refinance (if owner-occupied) | MLI Select |
| Best for | Owner-occupiers wanting one rental unit with the least complexity | Conversions where a fourth unit will not fit | Long-term rental investors building new | Deeper lots where longer amortization makes the numbers work |
The City’s own feasibility work found many multiplex financial models come out negative unless the land is already owned, or the project uses a 4 + 1 configuration. That is the honest starting point: multiplexes work best for people who already own the lot and plan to hold the building for the long term.
How to get a real number for your property
- Start with the lot. Zoning envelope, trees, side yards, electrical service and drainage decide what can be built before anyone talks about finishes.
- Decide conversion vs. new build with an honest assessment of the existing house.
- Choose the unit count with the rebates and financing in mind, not just the rent.
- Get an itemized estimate that separates hard costs, soft costs, City charges and contingency, so your lender and accountant can work with it.
- Talk to a mortgage professional and a tax advisor before you commit, especially if you plan to rely on the HST rebate or MLI Select.
Planning a multiplex in Toronto?
We design and build Toronto multiplexes from custom plans or the City’s pre-approved designs, and every project starts with a lot assessment and an itemized estimate. Book a free consultation to find out what your property can support. You may also find our guides to renovation value and ROI and renovation timelines useful.
Multiplex cost FAQs
How much does it cost to build a fourplex in Toronto?
It depends on whether you convert or build new, the lower level, servicing and site conditions. As a benchmark, Altus Group’s 2026 guide puts GTA wood-frame residential hard costs at $210 to $330 per square foot before land, soft costs and HST, and small infill projects tend to sit at the higher end or above. An itemized estimate for your lot is the only reliable number.
Do multiplexes pay development charges in Toronto?
Units two through six are exempt in developments of up to six units. The first unit is not, although a demolition credit often offsets it.
Can I get the HST rebate on a triplex?
No. The purpose-built rental rebate requires at least four units with private kitchens, baths and living areas (or ten or more units), and duplexes and triplexes are specifically excluded.
Can I live in one unit of my fourplex and still get the HST rebate?
Generally not. At least 90% of units must be held for long-term rental, and the CRA’s own example shows an owner-occupied fourplex failing that test. Get tax advice for your situation.
Does MLI Select work for a fourplex?
Not on its own. MLI Select starts at five units. A fourplex plus a garden or laneway suite can reach that threshold.
How much can I borrow with the CMHC refinance?
Up to 90% of the property’s value after the work is done, for up to four units, with the as-improved value under $2 million, a maximum 30-year amortization and one unit occupied by you or a family member.
Is a conversion cheaper than a new build?
Often, but not always. A conversion avoids demolition and new foundations, but it can be expensive if the basement needs lowering or the structure, wiring and plumbing all need replacing. It also usually rules out the HST rental rebate.