Bench Footing vs. Underpinning: Which is Better for London Basements?
Last reviewed: April 17, 2026 | Editorial team: London Legal Basements Research Desk | Primary sources: City of London, Ontario Building Code, LTB.
If your basement ceiling is under 1.95m (6'5"), your secondary suite fails the Ontario Building Code (OBC). To legally rent the unit, you must lower the concrete floor. In London, this leaves property investors with two structural choices: Bench Footing or Underpinning.
What is Underpinning?
Underpinning involves excavating below the existing foundation wall (typically 1.2m deep) and pouring new concrete directly beneath it in sequenced sections.
- The Pros: It maintains maximum livable square footage and results in seamless, flat walls.
- The Cons: It carries the highest cost, the longest timeline, and the maximum structural risk to the property.
What is a Bench Footing?
A bench footing leaves the original foundation intact and builds a reinforced concrete "bench" inward along the perimeter. This bench is typically 0.5m wide and 1.0m high.
- The Pros: It is significantly cheaper and faster than underpinning, and carries a lower structural risk.
- The Cons: It permanently eats into your livable floor space by creating a concrete ledge around the walls.
Deep Dive: Lowering your floor is just one part of meeting the OBC. You must also account for egress windows and fire separations. Read our complete Guide to Meeting the 1.95m OBC Rule, review the OBC Fire Separation Guide, or check your window dimensions using our Free Egress Calculator.
Related Compliance Guides
- 1.95m OBC requirements and inspection standards
- Fire separation rules that apply after structural work
- What happens if structural work was done unpermitted
- How heritage-area basements handle structural upgrades
Download the OBC Planning PDF
Review the exact architectural diagrams for underpinning and egress. Enter your email to download the official OBC Basement Planning Guide PDF.