Building · Cost Guide
How Much Does Basement Second Unit Cost in Ontario?
Basement Second Unit costs in Ontario range from $80,000 – $175,000 per project. Prices vary by scope, city, and site conditions.
$80,000+
Starting price
4-8 months
Timeline
20%
Recommended contingency
Basement Second Unit Cost Breakdown
| Scope | Low | High | Unit | Labour | Material |
|---|---|---|---|---|---|
| Legal basement apartment (complete) | $80,000 | $175,000 | per project | 55% | 45% |
| Budget basement conversion (no lowering) | $50,000 | $80,000 | per project | 55% | 45% |
| Premium basement unit (high-end finishes) | $150,000 | $250,000 | per project | 50% | 50% |
| Underpinning + conversion (combined) | $125,000 | $225,000 | per project | 58% | 42% |
Price Ranges at a Glance
Legal basement apartment (complete)
Budget basement conversion (no lowering)
Premium basement unit (high-end finishes)
Underpinning + conversion (combined)
What's Included vs Not Included
Typically Included
- Building permit and ESA/TSSA inspections
- Separate entrance construction
- Fire separation (1-hour rated walls and ceiling)
- Separate electrical panel and circuits
- Kitchen rough-in and finishes
- Bathroom (full) with plumbing
- Egress windows meeting OBC requirements
- HVAC (separate zone or independent system)
- Smoke and CO detectors (hard-wired, interconnected)
- Insulation and drywall
- Flooring, trim, and paint
Not Included (Extra Cost)
- Underpinning (if ceiling height insufficient)
- Waterproofing (if moisture issues exist)
- Appliances (stove, fridge, dishwasher)
- Laundry hookup and washer/dryer
- Landscaping for separate entrance
- Municipal development charges (some cities)
- Zoning compliance review ($500-$2,000)
Basement Second Unit Cost by City
Prices adjusted for local labour rates and material costs across 15 GTA cities.
| City | Low | High | vs Toronto | Details |
|---|---|---|---|---|
Toronto City of Toronto | $80,000 | $175,000 | 0% | View |
Mississauga Peel Region | $76,200 | $166,688 | -5% | View |
Brampton Peel Region | $74,160 | $162,225 | -8% | View |
Vaughan York Region | $77,880 | $170,363 | -3% | View |
Markham York Region | $77,440 | $169,400 | -3% | View |
Richmond Hill York Region | $77,080 | $168,613 | -4% | View |
Aurora York Region | $75,400 | $164,938 | -6% | View |
Oakville Halton Region | $81,320 | $177,888 | +2% | View |
Burlington Halton Region | $76,720 | $167,825 | -4% | View |
Milton Halton Region | $74,160 | $162,225 | -8% | View |
Ajax Durham Region | $72,920 | $159,513 | -9% | View |
Pickering Durham Region | $74,160 | $162,225 | -8% | View |
Oshawa Durham Region | $71,240 | $155,838 | -12% | View |
Whitby Durham Region | $72,480 | $158,550 | -10% | View |
Hamilton City of Hamilton | $72,120 | $157,763 | -10% | View |
Permit & Engineering Costs
Building Permit (Second Unit Conversion)
Municipal building department
Fee based on project value. Includes plan review and 4-5 inspections (framing, insulation, final, re-inspections if needed).
$800-$2,000
Electrical Safety Authority (ESA) Permit
ESA
Required for new sub-panel and circuits. Contractor pulls permit. Includes rough-in and final inspection.
$150-$300
Plumbing Inspection
Municipal or private inspector (depends on jurisdiction)
Verifies drain slope, vent sizing, fixture installation, backwater valve if required.
$100-$200
Gas Permit (if applicable)
TSSA
Required if adding gas appliances (furnace, stove, water heater). Includes pressure test and appliance inspection.
$80-$150
HVAC Permit (if new system)
TSSA or municipal
Required for new furnace or significant ductwork modifications.
$75-$150
Money-Saving Tips
Stack rebates: federal MHRTC ($7,500) + provincial ($40,000 forgivable loan) + CMHC refinancing.
Check ceiling height before committing — 1.95m (6'5") minimum. Below that means underpinning.
Separate entrance is required by code — plan the location early as it affects exterior costs.
Fire separation is non-negotiable — 1-hour rated assembly between unit and main house.
Rent revenue of $1,500-$2,500/month means payback in 3-7 years depending on build cost.
Related Cost Guides
Basement Second Unit Cost FAQs
Does Bill 23 mean I don't need a building permit for a second unit?
No. Bill 23 (More Homes Built Faster Act, 2022) prohibits municipalities from restricting second units in most residential zones and removes parking requirements near transit — but you still need a building permit. Fire separation, egress, plumbing, electrical, and structural work all require permits and inspections. Bill 23 removes zoning barriers; it doesn't remove building code requirements.
Can I convert my basement without underpinning if the ceiling is only 6'8"?
No. OBC requires 1.95m (6'5") finished ceiling height for habitable rooms (bedrooms, living rooms, kitchens). With drywall, flooring, and framing, you need 7'2" rough minimum. A 6'8" basement can only be finished as storage, mechanical, or laundry space — not as living space. Attempting to permit a 6'5" finished height will fail plan review. Some contractors will build it without permits — you're left with an illegal unit that can't be rented legally, won't pass a home inspection if you sell, and poses liability if there's a fire.
Is a 1-hour fire rating really necessary? My cousin finished his basement with regular drywall.
Yes, it's necessary — and your cousin's basement is a life-safety hazard. Fire ratings are based on testing: a 1-hour assembly contains fire and limits temperature rise on the unexposed side for 60 minutes. This gives occupants time to escape and firefighters time to respond. Regular 1/2" drywall fails in 15-20 minutes. If a fire starts in the upper unit, basement occupants are trapped. Ontario Fire Marshal statistics show basement fires kill because people can't get out — fire separation buys time.
Can I use the existing furnace and electrical panel for both units?
Electrical: maybe, if the panel has capacity. Calculate the load: existing house draws + new unit draws. If total load exceeds 80% of panel rating, you need a service upgrade or sub-panel. Most 100A panels can't handle two full units — upgrade to 200A ($3K-$5K). HVAC: technically yes, but extending existing forced air often overloads the furnace and creates comfort issues (one thermostat controlling two units = constant arguments). Mini-split heat pumps ($4K-$7K) provide independent control and are more efficient. Some municipalities require separate heating systems for fire safety — check local bylaws.
Do I need a separate entrance, or can tenants use the main entrance?
OBC does not require a separate entrance — but most tenants (and landlords) prefer one for privacy and autonomy. A shared entrance complicates access, noise, and security. Walk-out basements can add an exterior door easily ($3K-$5K). Basements fully below grade need excavation, stairs, and possibly cutting through foundation ($8K-$15K). Some municipalities require separate entrances for rental licensing — Toronto does not, but encourages it.
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