Basement Apartment Conversion in Toronto & the GTA
Turn your basement into a legal rental apartment — from underpinning to occupancy permit.
Converting a basement into a legal secondary suite is one of the smartest investments a GTA homeowner can make. With rental demand at historic highs across Toronto and surrounding cities, a legal basement apartment can generate $1,500–$2,500+ per month in rental income while significantly increasing your property value. Ontario's updated Building Code and municipal zoning reforms have made basement apartments more accessible than ever, but the requirements are stringent: minimum ceiling heights (typically 6'5" to 7'0" depending on municipality), separate entrance, fire separation between units, egress windows, independent HVAC, and multiple inspections. Most older GTA basements don't meet these requirements without underpinning for ceiling height and significant renovation for code compliance. Buildoreno provides turnkey basement apartment conversion — from the initial underpinning to increase ceiling height, through plumbing, electrical, HVAC, fire separation, finishing, and final occupancy permit. We handle engineering, permits, inspections, and all trades coordination so you get a fully legal, rent-ready apartment.
What you get, done right
What basement apartment conversion costs across the GTA
Median project pricing in each of our busiest markets. Your exact number depends on scope, access, and site conditions — every Buildoreno quote is free, written, and itemized.
| City | Price range | Full guide |
|---|---|---|
| Toronto | $65,000–$90,000 | View → |
| Mississauga | $65,000–$92,000 | View → |
| Brampton | $60,000–$85,000 | View → |
| Vaughan | $53,000–$76,000 | View → |
| Oakville | $68,000–$96,000 | View → |
| Markham | $52,000–$74,000 | View → |
Median project pricing. See each city guide for the full small / medium / large breakdown.
Our process, step by step
- 1Feasibility & Planning
We assess your basement's current ceiling height, egress potential, plumbing access, and electrical capacity. We verify zoning compliance with your municipality and develop a complete scope of work with engineering requirements.
- 2Underpinning (if needed)
If ceiling height is below code minimum, we underpin the foundation to achieve the required height. This is the most significant phase — typically 4–8 weeks — and must be completed before interior work begins.
- 3Rough-In Construction
Framing, fire-rated assemblies between units, plumbing rough-in (kitchen, bathroom, laundry), electrical panel and circuits, HVAC ductwork or split system installation, and egress window cutting if needed.
- 4Finishing & Inspection
Drywall, flooring, kitchen installation, bathroom finishing, painting, and trim. Multiple inspections occur throughout: framing, plumbing, electrical, HVAC, insulation, fire separation, and final occupancy.
- 5Occupancy Permit
We coordinate the final inspection and obtain the occupancy permit that makes your basement apartment legal. You receive all documentation needed for insurance and rental purposes.
What it costs
Every Buildoreno estimate is a free, itemized written quote — no hidden line items. Your exact price depends on site conditions, materials, and scope.
See the full underpinning cost guide →Last updated: March 2026
Basement Apartment Conversion questions, answered
Most GTA municipalities now permit secondary suites in some form, though rules vary. Toronto, Mississauga, Brampton, and many others have updated zoning to allow basement apartments. Restrictions may apply to lot size, parking, and building type. We verify compliance for your specific property before starting.
Ontario Building Code requires minimum 6'5" (1.95m) clear height for habitable rooms in secondary suites, though many municipalities require 7'0" (2.13m). If your basement doesn't meet this, underpinning is required before conversion. We measure and advise during the feasibility assessment.
With underpinning: 4–6 months total (underpinning: 6–8 weeks, construction: 8–12 weeks, inspections and permits: 2–4 weeks). Without underpinning: 3–4 months. Timeline depends on municipal permit processing speed and inspection scheduling.
At current GTA rental rates of $1,500–$2,500/month, a $120,000 investment generates $18,000–$30,000/year in gross rental income. The conversion typically pays for itself within 4–7 years while increasing your property value by $50,000–$150,000 — making it one of the highest-ROI home improvements available.
Yes. Ontario Building Code requires a separate entrance for secondary suites. This can be an exterior entrance (side or rear of house) or through a shared interior vestibule with fire-rated separation. Exterior entrances are preferred for tenant privacy and are required in some municipalities.
Ready to unlock
your basement?
Book a free basement assessment. We'll measure your existing ceiling height, explain whether you even need to underpin, and walk you through the engineered, permitted process.
Call (647) 254-0877