A legal basement apartment — also called a secondary suite, basement suite, or in-law apartment — is one of the highest-ROI investments a Canadian homeowner can make. In Ontario, a legal basement apartment can generate $1,200–$2,200/month in rental income while adding $80,000–$150,000 to your home's appraised value. But getting it done legally is essential: illegal basement apartments can void your insurance, expose you to huge fines, and create serious liability. Here's everything you need to know.
| Category | Cost Range | Notes |
|---|---|---|
| Separate Entrance Construction | $5,000–$20,000 | Required for most municipalities. Includes excavation, egress door, exterior stairs, and waterproofing. |
| Egress Windows | $2,000–$6,000 | Bedrooms must have proper egress windows (min. 0.35m² opening). Each window: $800–$2,500 installed. |
| Plumbing (Kitchen + Bathroom) | $8,000–$20,000 | Full kitchen and bathroom rough-in. Backwater valve is required by code in most Ontario municipalities. |
| Electrical Panel & Suite Wiring | $5,000–$12,000 | Separate electrical panel for suite, smoke/CO detectors, ESA permit and inspection required. |
| Ceiling Height Modifications | $0–$30,000 | Ontario requires minimum 6'5" (1.95m) ceiling height. Underpinning to lower the floor is the most expensive part of many conversions. |
| Spray Foam Insulation | $3,000–$8,000 | Required for thermal and fire separation. Rim joists and exterior walls must be properly insulated. |
| Fire Separation (Drywall) | $3,000–$8,000 | The ceiling and shared walls must have minimum 30-minute fire separation using Type X drywall. |
| Finishes (Flooring, Kitchen, Bath) | $15,000–$35,000 | LVP flooring, kitchen cabinets and countertop, bathroom vanity and fixtures, paint throughout. |
Check building permit requirements, fees, and timelines for your specific city across 800+ Canadian municipalities.
View Permit Requirements →Ontario's Building Code requires a minimum ceiling height of 1.95m (6'5") in habitable rooms. Many older basements have 6'0"–6'3" ceilings. Underpinning (lowering the floor by digging down) costs $20,000–$50,000 and is the single largest cost driver in basement conversions.
Most Ontario municipalities require a separate entrance for a legal second unit. This typically means a side-door or rear entrance with proper exterior stairs — not just a door at the bottom of your interior stairs. Budget $5,000–$20,000 depending on your home's layout.
Expect 4–12 weeks to get a building permit for a basement apartment in Ontario, depending on the municipality. Toronto can take longer. Start the permit process before finalizing your contractor — your contractor can help prepare the permit drawings.
Most Ontario municipalities now permit secondary suites by right (no rezoning needed) under the More Homes Built Faster Act. However, some municipalities have additional requirements around parking, lot size, and suite size. Check your local municipality's zoning bylaw.
Once you rent the suite, Ontario's Residential Tenancies Act applies. You'll need to register with your municipality's rental licensing program (if applicable), provide a standard lease, and follow Ontario's rent increase guidelines. Budget for a landlord insurance policy ($50–$100/month).
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Find Contractors →A legal basement apartment in Ontario must comply with the Ontario Building Code and your local zoning bylaws. Key requirements: minimum 1.95m ceiling height, proper egress windows in bedrooms, a separate entrance, fire separation between units (30-minute minimum), interconnected smoke and CO detectors, a legal kitchen and bathroom, and a building permit with all inspections passed.
Yes — a building permit is required for any new secondary suite in Ontario. You'll also need an electrical permit (ESA), and potentially a plumbing permit. Working without permits is illegal, can void your home insurance, and makes the unit unlawful to rent. Your contractor should help prepare the permit application and drawings.
Rental rates vary by city and suite quality. In the GTA, a one-bedroom legal basement apartment typically rents for $1,800–$2,400/month. In smaller Ontario cities (Hamilton, London, Kingston), expect $1,200–$1,800/month. A well-finished suite with a separate entrance commands a significant premium over unfinished or semi-legal suites.
From start to finish, expect 4–8 months: 4–12 weeks for permit approval, 8–16 weeks for construction, plus 2–4 weeks for inspections and any deficiency corrections. Factor this into your timeline before committing to a tenant move-in date.
Ontario's Building Code requires a minimum ceiling height of 1.95m (6 feet 5 inches) in all habitable rooms — bedrooms, living rooms, and kitchens. Bathrooms require 2.1m in the shower/tub area. Many older basements don't meet this requirement, making underpinning (lowering the floor) necessary — a costly but often worthwhile investment.
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