Can a Toronto row house add a basement unit?

Yes, Toronto row houses can absolutely add a basement unit — this is one of the most popular ways homeowners in the city add rental income or multigenerational living space.

Toronto's zoning rules have become significantly more permissive in recent years. Under the City of Toronto's "as-of-right" zoning permissions, most residential properties — including row houses (also called townhouses or semi-detached homes) — are permitted to add a second unit without requiring a rezoning or Committee of Adjustment approval. This applies across most residential zones in the city, meaning if your row house sits in an R, RD, RS, or similar zone, you're likely already permitted to proceed.

What the Rules Require

The basement unit must comply with the Ontario Building Code (OBC) and Toronto Municipal Code Chapter 150, which sets out minimum standards for secondary suites. Key requirements include a minimum ceiling height of 1.95 metres (roughly 6'5"), though 2.1 metres is strongly preferred for livability and easier approval. Each unit must have its own separate entrance, proper egress windows in sleeping areas (minimum 0.35 m² opening), and dedicated smoke and carbon monoxide detectors on every level.

Mechanical separation is also required — meaning the basement unit needs its own heating source (a separate furnace, electric baseboard, or ductless mini-split), and ideally its own electrical panel or at minimum a sub-panel. All electrical work must be permitted through the ESA (Electrical Safety Authority), and any gas work requires a TSSA-licensed technician.

Toronto-Specific Considerations for Row Houses

Row houses present a few unique challenges compared to detached homes. The shared party walls mean you'll need to ensure proper fire separation (typically a 1-hour fire-rated assembly) between your unit and your neighbour's structure. Depending on the age of your home — many Toronto row houses in neighbourhoods like Cabbagetown, Leslieville, Riverdale, and The Junction date back to the late 1800s — you may also encounter low ceiling heights, rubble stone foundations, or knob-and-tube wiring that needs upgrading before a unit can be legally occupied.

Parking is often raised as a concern, but Toronto removed mandatory parking requirements for secondary suites in most areas, so you typically don't need to add a parking space.

Typical costs for a basement conversion in a Toronto row house run $80,000–$150,000+ depending on the scope. A basic conversion with existing height and good bones might come in at the lower end, while a full underpinning project (to gain ceiling height) can push well past $150,000 on its own.

Your Next Steps

Start by pulling your property's zoning information at toronto.ca/zoning to confirm your designation, then contact Toronto Building (416-397-5330) to discuss permit requirements. You'll need a building permit — no exceptions — which protects you legally, ensures proper inspections, and is essential if you ever sell or make an insurance claim.

From there, get a structural assessment if your foundation is older, and consult with a contractor experienced in Toronto secondary suites. You can find licensed professionals through the Toronto Construction Network directory who specialize in exactly this type of project.