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Real Estate Investors - ADU Builders
Garden suites, laneway homes, basement and secondary suites built for real estate investors across the 30 municipalities of the Greater Toronto Area - zoning review, permit drawings and construction handled by one team.
Why Real Estate Investors Chooses GTA ADU Builders
Key Takeaways
- Key features: Adding a third unit to an existing legal duplex, Feasibility review across a portfolio of GTA lots, Laneway build underwritten against projected rent
Investors adding a income-generating unit to an existing rental property. We start with a feasibility and lot review that states what the zoning allows, what the build costs and what the unit rents for before you commit capital.
Common Use Cases
- Adding a third unit to an existing legal duplex
- Feasibility review across a portfolio of GTA lots
- Laneway build underwritten against projected rent
- Value-add ADU completed before refinancing
Key takeaways
- Investors adding an income unit to an existing rental: on an investment file the wrong answer is not an ugly building, it is a negative spread discovered after the foundation is poured.
- The underwriting inputs are known and quoted the same way every time - $200,000-$350,000 for a detached 500-600 sq ft suite, internal suites far lower, the whole category spanning $40K to $450K.
- Use eight to fourteen months end to end in a carry-cost model, not the four-to-eight-month construction duration alone.
- As-of-right is not unconstrained: servicing capacity, lot coverage and permit fee bands vary by municipality, a common rule caps the additional unit at 40% of the main building footprint, and a ravine lot can add a season.
Investors adding an income-generating unit to an existing rental property. We start with a feasibility and lot review that states what the zoning allows, what the build costs and what the unit rents for before you commit capital - because on an investment file the wrong answer is not an ugly building, it is a negative spread discovered after the foundation is poured.
The underwriting inputs are known and we quote them the same way every time. A detached suite of 500 to 600 sq ft runs roughly $200,000 to $350,000 across the Greater Toronto and Hamilton Area, the figure Resimate CEO Sarah Cipkar gave CBC News in July 2025, or $300 to $600 per square foot depending on site access and finish. Internal secondary suites sit far lower; the whole category spans $40K to $450K. Permit review is four to eight weeks, construction four to eight months, and eight to fourteen months end to end - which is the number that belongs in a carry-cost model, not the construction duration alone.
Use cases
- Adding a third unit to an existing legal duplex
- Feasibility review across a portfolio of GTA lots
- Laneway build underwritten against projected rent
- Value-add ADU completed before refinancing
Bill 23, the More Homes Built Faster Act (2022), is what made the third unit underwritable. Ontario municipalities must permit up to three residential units as-of-right on most serviced lots holding a detached, semi-detached or townhouse dwelling, so the standard investor play - existing duplex plus one detached unit - no longer depends on a rezoning application that used to run six to twelve months and could be refused outright. O. Reg. 299/19 as amended in November 2024 governs additional residential units, and O. Reg. 462/24 harmonises municipal by-laws against province-wide garden-suite criteria.
As-of-right is not the same as unconstrained, and the constraints are where portfolio feasibility earns its fee. Servicing capacity, lot coverage, setbacks and permit fee bands vary municipality to municipality across the GTA. A common size rule caps the additional unit below the primary dwelling, frequently at 40% of the main building footprint. Since 1 April 2024 the amended Conservation Authorities Act requires TRCA or Credit Valley Conservation sign-off inside regulated areas - a ravine or Oak Ridges Moraine lot can add a season to the schedule and should be priced as a risk, not discovered as a surprise.
There is policy evidence behind the demand side. CMHC's Spring 2026 Housing Supply Report records Canadian housing starts rising 6% in 2025 with ground-oriented starts up while condo starts weakened, and credits local policy changes allowing laneway homes and secondary suites for ground-oriented growth in at least one CMA. We carry WSIB registration and $2M general liability, and issue a clearance certificate on request - under the Construction Act and the WSIA an owner is liable for an unregistered contractor's unpaid premiums, and the certificate must be re-verified every 90 days.
Real Estate Investors - Permits and Approvals by Municipality
Approval costs and lot conditions in the GTA municipalities where we build most often for this use.
| Municipality | Typical approval fees | Lot typology |
|---|---|---|
| Toronto | $8,000-$14,000 in permit, development and plan-review fees | Narrow downtown lots with rear public laneways - Toronto has over 300 km of them, more laneway frontage than any other Canadian city. |
| Brampton | $5,500-$10,000 including Brampton registration and Peel charges | Deep newer-subdivision lots, many with an existing unregistered basement apartment that must be brought to Ontario Building Code fire-separation standard. |
| Mississauga | $6,500-$11,000 in City of Mississauga and Region of Peel charges | Large 1970s-90s subdivision lots with attached garages; garage conversions and rear coach houses are both common outcomes. |
| York | $8,000-$14,000 under the City of Toronto fee schedule | Older narrow semi-detached lots on a laneway grid, with frequent shared-driveway conditions that must be resolved before permit. |
| Etobicoke | $8,000-$14,000 under the City of Toronto fee schedule | Split personality - laneway-served lakeshore grid in Mimico and New Toronto, versus large treed lots in The Kingsway where garden suites dominate. |
| Ajax | $7,000-$12,000 including Durham Region charges | Compact 1990s-2000s subdivision lots where the required 1.2 m side-yard construction access sets the maximum module width we can crane in. |
| King | $9,000-$16,500 including York Region and septic charges | Estate and agricultural parcels, many over an acre, on private well and septic with moraine core-area restrictions. |
| North York | $8,000-$14,000 under the City of Toronto fee schedule | Deep post-war bungalow lots, commonly 50 ft × 120 ft, with rear yards large enough for a detached garden suite plus the required 1.5 m separation. |
Fee bands are indicative, drawn from project experience - confirm current tariffs with the municipality before budgeting.
Recommended Unit Types
Frequently Asked Questions
Everything you need to know about our services.
Investors adding a income-generating unit to an existing rental property. We start with a feasibility and lot review that states what the zoning allows, what the build costs and what the unit rents for before you commit capital. The situations we see most often: adding a third unit to an existing legal duplex; feasibility review across a portfolio of gta lots; laneway build underwritten against projected rent; value-add adu completed before refinancing.
Related service: Accessory Dwelling Units
Our estimate band on a 700 sq ft reference unit runs $268,000-$359,500 in Brock to $281,500-$377,000 in East York, about $383-$402 per square foot. This scope involves a new foundation, new servicing and a full building envelope. Municipal approvals are quoted on top and separately, between $5,500-$10,000 including Brampton registration and Peel charges and $9,000-$16,000 including Peel Region and septic permit charges depending on the municipality.
Related service: Our ADU services
On most serviced GTA lots, yes. Bill 23 and O. Reg. 299/19 permit up to three residential units as-of-right on a lot already holding a detached, semi-detached or townhouse dwelling.
What actually decides it is the local by-law's rear-yard coverage, setback and height limits, plus conservation-authority screening (TRCA, Credit Valley, LSRCA) where the lot is in a regulated area. We check all of that before design starts, not after.
Related service: Our ADU services
It depends on the lot rather than on the preference. A rear yard with clear access supports a detached garden suite or laneway house; an existing garage on a sound slab makes a conversion the cheapest legal route; a full-height basement with a walk-out is the fastest path to a permitted interior suite. We give the answer at the feasibility review, with the by-law citation behind it.
Related service: Laneway Homes
Eight to fourteen months end to end - design, four to eight weeks of plan review, then construction - across all 30 GTA municipalities we serve. Excavation is scheduled inside the local building season; interior work continues through winter.
Related service: Our ADU services
Ready to Get Started?
Building for real estate investors? As adu builders across the GTA we scope the ADU that fits your lot - zoning check, permit drawings and construction.