What Is a Legal Basement Apartment?
A legal basement apartment (also known as a secondary suite or accessory dwelling unit) is a self-contained residential unit located in the basement of a single-family, semi-detached, or row house that fully complies with:
Ontario Building Code (OBC)
Ontario Fire Code
City of London Zoning By-law
Electrical Safety Authority (ESA)
A legal basement apartment must have its own kitchen, bathroom, sleeping area, safe exits, proper ceiling height, and fire separation from the main dwelling.
Is a Basement Apartment Legal in London, Ontario?
Yes. Basement apartments are legal in London, Ontario, provided the property and renovation meet all municipal and provincial requirements.
Key zoning points:
Most residential zones in London allow one secondary dwelling unit
The home must typically be owner-occupied (varies by zone)
Minimum parking requirements may apply
The unit must be registered with the City after approval
Zoning compliance is the first step before any construction begins.
Permit Requirements Overview
To legalize or build a basement apartment in London, you will need:
Building Permit (City of London)
Plumbing Permit (if altering or adding plumbing)
HVAC approval (if modifying ductwork)
ESA Electrical Permit
Fire inspection approval (as part of final occupancy)
Important: Working without permits can result in fines, stop-work orders, and forced removal of completed work.
Ontario Building Code Requirements
A legal basement apartment must meet strict OBC standards, including:
Ceiling Height
Minimum 6 ft 5 in (1.95 m) over most living areas
Beams and ducts may allow limited reductions
Windows & Natural Light
Proper window size for bedrooms
Minimum glass area relative to room size
Entrances & Exits
Separate entrance or shared entrance with fire-rated separation
At least one egress window or door for bedrooms
Soundproofing
Minimum STC 50 sound separation between units
Often achieved with resilient channel, insulation, and double drywall
Fire & Safety Requirements
Fire safety is one of the most critical components of basement apartment legalization.
Requirements include:
30–45 minute fire-rated separation between units
Interconnected smoke alarms in all required areas
Carbon monoxide detectors near sleeping areas
Self-closing, fire-rated doors where applicable
Proper fire stopping around pipes and duct penetrations
Failure to meet fire code is the #1 reason inspections fail.
Step-by-Step Process
1. Zoning Review
Confirm your property is eligible for a legal basement apartment.
2. Design & Drawings
Architectural or BCIN-qualified designer prepares permit drawings.
3. Permit Application
Submit drawings to the City of London Building Department.
4. Construction Phase
Renovation begins according to approved plans.
5. Required Inspections
Framing
Insulation
Plumbing
Electrical (ESA)
Final building inspection
6. Registration & Occupancy
Once approved, the unit becomes a legal rental apartment.
Cost of a Legal Basement in London
Typical cost range (2026 estimates):
Basic legalization: $50,000 – $70,000
Mid-range renovation: $70,000 – $90,000
High-end finish: $90,000 – $120,000+
Cost factors include:
Lowering basement floor
Adding separate entrance
Fire separation upgrades
Plumbing & electrical changes
Timeline & Inspections
Design & zoning review: 2–4 weeks
Permit approval: 4–8 weeks
Construction: 8–12 weeks
Final inspections: 1–2 weeks
Total timeline: ~4–6 months
Delays often occur due to incomplete drawings or failed inspections.
Common Mistakes to Avoid
Starting construction without permits
Ignoring fire separation requirements
Inadequate ceiling height
Non-compliant bedroom windows
Hiring unlicensed contractors
Fixing these mistakes after the fact can be extremely costly.
Call to Action – Free Consultation
Thinking about building or legalizing a basement apartment in London, Ontario?
👉 Book a FREE consultation today and get:
Zoning eligibility check
Rough cost estimate
Permit guidance
Inspection-ready design strategy
Contact us now to turn your basement into a safe, legal, income-generating apartment.
Call Us: 519-494-3673
Email: info@londonrenovations.ca
Location: Serving London, Ontario and surrounding areas
Book a Free Estimate Online
FAQ – Legal Basement Apartment London Ontario
1 Can I legalize an existing basement apartment?
Yes, but it must be upgraded to meet current building and fire codes.
2 Do I need a separate hydro meter?
No, but it is optional.
3 Is basement lowering always required?
No. Only if ceiling height is insufficient.
4 Can I rent to students?
Yes, as long as zoning and occupancy limits are respected.
Let’s Build Something Great
As your general contractor in London, Ontario, we manage the heavy lifting so you can enjoy the results. Let’s discuss your project — with zero pressure and expert advice from day one.