Cost Guides · 10 min read · 2025-11-20
A legal basement apartment can generate $1,600–$2,700 per month in the GTA — but only if it meets Ontario Building Code and fire code requirements. Here is what it takes to build one legally, what it costs in 2026, and whether the math works.
With Toronto rents remaining among the highest in Canada, converting a basement into a legal second suite has become one of the most financially compelling renovation projects in the GTA. Bungalows in Scarborough, North York, and Etobicoke — with their separate side entrances and generous basement footprints — are especially well suited to conversion, which is a big part of why they remain in such demand.
But there is a large gap between a finished basement with a kitchenette and a legal, registered second suite. An illegal unit exposes you to fines, insurance problems, and orders to vacate your tenant. This guide covers what Ontario and Toronto actually require, what a legal conversion costs in 2026, and what rental income you can realistically expect.
A legal second suite must comply with the Ontario Building Code, the Ontario Fire Code, and local zoning. Second suites are now permitted as-of-right in most residential zones across Toronto and much of the GTA, but the unit itself must meet specific physical requirements:
A legal conversion starts with permit drawings prepared by a qualified designer (typically $2,500–$6,000), followed by a building permit application. The City reviews for zoning compliance and Building Code conformity, and once construction starts you will have multiple inspections — framing, insulation, plumbing, HVAC, electrical (through the Electrical Safety Authority), and final occupancy.
Expect the full process — design, permits, construction, and final inspections — to take 4 to 8 months. Skipping permits to save time is a false economy: unpermitted units routinely surface during insurance claims, refinancing, or resale, and retrofitting compliance after the fact costs more than doing it right the first time.
For a basement that already has adequate ceiling height and a separate entrance, a legal conversion in the GTA typically costs $65,000–$95,000. That covers fire separation, a full kitchen and bathroom, egress windows, flooring, electrical upgrades, interconnected alarms, and permit fees.
If your basement needs more foundational work, budget $95,000–$130,000 or beyond. Underpinning to gain ceiling height runs $380–$480 per linear foot and can add $55,000–$85,000 on its own. A new separate entrance with excavation, stairs, and waterproofing adds $16,000–$32,000. A separate laundry, upgraded 200-amp electrical service, or a secondary heating system each add several thousand more.
As a rough benchmark, most homeowners in Scarborough, North York, and Mississauga completing a full legal conversion in 2026 land between $80,000 and $125,000 all-in.
A legal one-bedroom basement apartment in the GTA currently rents for $1,600–$2,100 per month, while a well-finished two-bedroom suite in a desirable area like East York, North York, or central Mississauga can fetch $2,100–$2,700. Legal units also rent faster and to stronger tenants, because tenants increasingly ask whether a unit is registered.
The ROI logic is straightforward: a $90,000 conversion generating $2,000 per month produces about $24,000 in gross annual rent — a payback period of roughly four to five years before considering the added resale value. Homes with legal, income-generating suites consistently command a premium in the GTA market, and lenders will often count a portion of the rental income toward your mortgage qualification.
Be honest in your projections: budget for vacancy, maintenance, slightly higher insurance, and income tax on the rent. Even with conservative assumptions, a legal basement suite remains one of the highest-return renovations available to GTA homeowners.
Basement conversions involve more moving parts than almost any other residential project — code compliance, fire separation, egress, plumbing, and inspections all have to line up. SimplifyReno matches you with verified, insured contractors who have completed legal second suites in the GTA and understand what inspectors look for. Start with a free AI-powered cost estimate in the app so you know whether your budget is realistic before committing.
As the project moves forward, milestone tracking shows you exactly which stage your conversion is at — from permits to framing to final inspection — while secure messaging keeps all decisions in writing and the Vault stores your drawings, permits, and inspection records for future refinancing or resale. Download SimplifyReno free on iOS and Android.