Basement Underpinning & Structural Alterations – Toronto
This project involved structural engineering services for a residential basement underpinning and interior alteration within an existing low-rise house in Toronto.
Parsways was retained to provide permit-ready structural design and detailing to support staged excavation, foundation stabilization, and temporary access requirements in accordance with OBC 2024.
Location: Toronto, Ontario
Completion: 2025
Sector: Residential – Interior Alteration & Foundation Works
1. The Challenge
The project presented several technical and construction-related constraints typical of older residential structures:
Existing Foundation Conditions:
The house was supported on a rubble stone foundation with limited original documentation.
Global Stability:
Underpinning needed to be performed in stages while maintaining stability of the existing and party walls.
Temporary Access:
A temporary foundation opening was required during construction, necessitating careful lintel and load transfer design without compromising the existing structure.
2. The Engineering Solution
Parsways developed a tailored, OBC-compliant structural solution focused on safety, constructability, and long-term performance.
a. Staged Basement Underpinning
A reinforced concrete underpinning system was designed with controlled pin lengths, curing cycles, and excavation sequencing to limit settlement and preserve the integrity of the existing rubble foundation.
b. Temporary Access Opening & Lintel Design
Independent lintel and temporary support details were engineered to safely redistribute loads during construction, allowing access without overstressing the existing foundation or framing.
3. The Outcome
The project resulted in a fully stamped, permit-ready structural package accepted by the local authority. The design minimized construction risk during excavation, provided clear sequencing for site execution, and ensured long-term structural stability in full compliance with OBC 2024 and applicable CSA standards.