Legal duplex conversion rental property
Timeline: 62 daysInvestment property

Legal Duplex Conversion - Rental Property

A strategic renovation that transformed a single-family home into a high-value legal duplex, maximizing rental income and resale potential.

“This duplex turned out better than we imagined. The rental potential and value increase are incredible.” — Client
The transformation

A strategic renovation that transformed a single-family home into a high-value legal duplex, maximizing rental income and resale potential.

This project began with a clear investment goal: convert an outdated single-family property into a fully compliant legal duplex that would significantly increase long-term value, generate strong rental income, and appeal to both investors and homebuyers. Our team handled the entire transformation — from planning and permits to construction and finishing — delivering a modern, functional, and profitable result.

Original project gallery

Before, during, and after.

Every image below is from the original Build Big case study.

Project goals
  • Create a second fully functional, code-compliant unit
  • Maximize rental income and ROI for the client
  • Improve safety, functionality, and marketability
  • Modernize both units with cohesive, contemporary finishes
  • Ensure full legal compliance (fire separation, egress, electrical, plumbing)
What we did

The work behind the transformation.

Full Basement Conversion to a Legal Second Unit

The original basement was outdated and underutilized. We transformed it into a bright, efficient apartment with:

  • A full kitchen
  • Separate laundry
  • New 3-piece bathroom
  • Legal egress window
  • Proper fire separation & soundproofing
  • Individual heating zones

This new unit meets all Ontario Building Code and fire safety requirements.

Structural, Plumbing & Electrical Upgrades

To ensure the home operates as two independent units, we completed:

  • Dedicated electrical panel setup
  • New plumbing runs for the second kitchen and bathroom
  • HVAC upgrades and additional ventilation
  • Reinforced floor structure
  • Smoke/CO detectors interconnected between units

These improvements increased efficiency and allowed the home to pass all inspections smoothly.

Complete Renovation of the Main Unit

The upper unit also received a full makeover:

  • New flooring and trim
  • Fresh paint throughout
  • Modern lighting and fixtures
  • Updated kitchen with new finishes
  • Refreshed bathroom

The result: a bright, stylish home ideal for owners or tenants.

Exterior Enhancements

To support the duplex layout and increase curb appeal, we added:

  • A dedicated entrance for the lower unit
  • Updated steps and exterior lighting
  • Driveway modifications for separate parking
  • Minor landscaping to freshen the exterior
The results

A completed space built for real life.

The property is now a fully legal, two-unit home with exceptional rental potential and strong resale value. Key benefits:

  • Two independent, modern living spaces
  • Low-maintenance finishes ideal for tenants
  • High return on investment for the client
  • A property that meets all legal and safety requirements
  • Significantly improved market appeal

The homeowner was thrilled with the transformation and impressed by how smoothly the project moved through planning, permit approvals, and final inspections.

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