Basement Permit Ontario — Legal Suite Conversion Guide (2025)

Converting your basement into a legal secondary suite is one of the best investments Ontario homeowners can make. A legal suite adds significant value, generates rental income, and brings the unit up to safety standards — but it requires a proper building permit and often structural engineering drawings.

Do I Need a Building Permit for a Basement Suite in Ontario?

Yes. Creating a legal basement suite in Ontario requires a building permit in virtually all municipalities. The permit process ensures the unit meets Ontario Building Code requirements for fire separation, egress windows, ceiling height, mechanical systems, and structural integrity.

When Is a Structural Engineer Required for a Basement Suite?

A structural engineer is required for a basement suite conversion when the project involves:

• Adding or enlarging a separate entrance through the foundation wall
• Lowering the basement floor (underpinning) to achieve minimum ceiling height
• Removing or modifying any load-bearing walls
• Adding a new window opening in the foundation wall for egress
• Any other modification to the structural elements of the home

What Is the Minimum Ceiling Height for a Legal Basement Suite in Ontario?

Ontario Building Code requires a minimum clear ceiling height of 1.95 metres (approximately 6'5") for habitable rooms in a basement suite. Many older Ontario homes have basement ceiling heights of only 5'6" to 6' — making underpinning necessary to create a legal suite. AMGH Engineering designs complete underpinning packages including permit drawings and rebar details.

AMGH Engineering's Track Record with Basement Permits

AMGH Engineering has completed over 200 basement permit applications — all approved on the first submission. We know what Ontario building examiners require and prepare our packages accordingly. Contact us to discuss your basement suite project.