Structural Design & Foundation Engineering for Additional Unit with Walkout – Richmond Hill
Parsways Inc. provided full structural design services for the construction of an additional residential basement unit with an independent exterior walkout at 57 Bloomfield Trail. The scope included foundation detailing, wall assemblies, fire separations, and structural modifications in accordance with OBC 2024.
The project required coordinated structural drawings and detailing to support permit approval and safe integration with the existing dwelling structure.
Location: Richmond Hill, Ontario
Completion: 2025
Sector: Residential
1. The Challenge
The project involved introducing a new basement residential unit with a dedicated exterior walkout within an existing home.
Walkout and Foundation Modifications:
Creating the exterior stair opening required new reinforced concrete foundation walls, lintel framing, and careful detailing around existing footings and structural elements.
Fire Separation and Code Compliance:
The new unit required compliant fire-rated floor and wall assemblies, including 30-min and 45-min fire-resistance-rated assemblies and STC-rated separations.
Site Drainage and Waterproofing:
The walkout configuration required sloped exterior grading, new weeping tile connections, waterproofing membranes, and insulation continuity to manage moisture and thermal performance.
2. The Engineering Solution
A coordinated structural and foundation design package was developed to address the new unit layout and walkout construction.
a) Structural & Foundation Design:
Reinforced concrete walls, new stair slabs, insulation, vapour barriers, and granular bases were detailed per OBC 2024 requirements.
b) Fire-Resistance & Acoustic Assemblies:
Floor and wall assemblies were specified to achieve required FRR and STC ratings with Type X gypsum, resilient channels, and sound insulation.
c) Drainage & Envelope Detailing:
Waterproofing included liquid bitumen membrane, dimpled membrane protection, horizontal insulation extensions, and new weeping tile tied into existing systems.
3. The Outcome
The project resulted in a fully coordinated, permit-ready structural design package for the additional residential unit. The reinforced foundation walls, compliant fire separations, and detailed walkout configuration enabled safe construction while maintaining structural integrity of the existing dwelling. The final design supported drainage, insulation continuity, and code-compliant life safety provisions under OBC 2024, allowing the project to proceed without structural revisions.