Ontario Building Code Part 11: Managing Performance Level Reductions and Renovations
Sarah's Expert Insight
OBC Compliance Specialist
"When planning occupancy changes or residential additions in regions like London or Muskoka, understanding Section 11.4 is critical to avoiding unexpected costs related to 'compensating construction.' As a senior consultant at empcontracting.ca Inc. your construction contractor in London, Ontario, I emphasize that any increase in bedroom count or floor area must be balanced against sewage system capacity to remain compliant with the 2024 Ontario Building Code."
Understanding the 2024 Ontario Building Code (OBC) is essential for any major renovation or change of use project. Specifically, Division B – Part 11 outlines the criteria for when a building's 'performance level' is considered reduced, necessitating further action or compensating construction. Whether you are working with a heritage property or modernizing a commercial space, empcontracting.ca Inc. your construction contractor in London, Ontario, ensures your project meets these stringent compliance standards.
Major Occupancy Changes and Construction Types
Combustible Construction and Group C Occupancies
According to Article 11.4.2.3., a building's performance level is deemed reduced if the occupancy of a combustible building is changed to a use that would normally require noncombustible construction. Furthermore, any change to a Group C (residential) major occupancy in a building exceeding three storeys is generally considered a reduction in performance level, unless specific egress and safety requirements are met.
Impact on Plumbing and Sewage Systems
Article 11.4.2.4 and 11.4.2.5 focus on the mechanical integrity of a building. The performance level is reduced if:
- Proposed extensions or material alterations adversely affect the existing plumbing.
- Alterations or increased occupant loads exceed the daily design sanitary sewage flow capacity of the existing system.
- In residential dwelling units, adding bedrooms, increasing the finished area by more than 15%, or adding new plumbing fixtures results in sewage flow exceeding system capacity.
Daily Design Sanitary Sewage Flow
Calculations must be performed in accordance with Article 8.2.1.3. to determine if the existing infrastructure can handle the proposed occupancy change or expansion. If the sewage system is prohibited from handling the new type of waste or volume, the performance level is officially reduced.
Building Extensions and Vertical Growth
For existing buildings of combustible construction, adding a storey that results in the building being more than four storeys high automatically triggers a reduction in performance level under Article 11.4.2.6. This is a critical factor for developers looking to densify urban lots in southwestern Ontario.
Compensating Construction Requirements
Under Article 11.4.3.1., whenever the performance level of an existing building is reduced via the conditions mentioned above, 'compensating construction' must be carried out. This ensures that the overall safety and structural integrity of the modified building meet the intent of the current Building Code.
Disclaimer: This content is generated from the Ontario Building Code for educational purposes. Always consult with a licensed professional engineer or your local building department before starting any construction project in London, Ontario.