OBC 2024 Guide: Minimum Footing Sizes and Adjustments for Ontario Residential Construction
Sarah's Expert Insight
OBC Compliance Specialist
"In regions like London and the lake-heavy Muskoka area, the soil's bearing capacity and water table levels are critical variables that empcontracting.ca Inc. meticulously evaluates. Failing to account for the mandatory 100mm to 150mm footing increases for masonry or ICF construction can lead to significant structural settlement, making these OBC adjustments a top priority during our site planning phase."
When preparing the foundation for a new build, understanding the 2024 Ontario Building Code (OBC) requirements for footing widths is essential for structural integrity. As empcontracting.ca Inc. your construction contractor in London, Ontario, we ensure every project adheres to these rigorous standards to prevent foundation settlement and failure.
Minimum Footing Sizes (Table 9.15.3.4.)
The base width of a strip footing is determined by the number of floors it supports. Under standard conditions, the following minimums apply:
- 1 Storey: 250 mm (Exterior), 200 mm (Interior)
- 2 Storeys: 350 mm (Exterior), 350 mm (Interior)
- 3 Storeys: 450 mm (Exterior), 500 mm (Interior)
High Water Table Adjustments
Per OBC 9.15.3.4.(3), if your foundation rests on gravel, sand, or silt where the water table is near the bearing surface, the footing width must be doubled. This is a critical factor for waterfront properties in areas like Muskoka or low-lying zones in London.
OBC 9.15.3.5: Adjustments for Exterior Wall Loads
Standard widths must be increased based on the type of construction being supported:
- Masonry Veneer: Increase width by 65 mm per storey.
- Full Masonry: Increase width by 130 mm per storey.
- ICF (Insulated Concrete Form): Increase width by 150 mm per storey.
OBC 9.15.3.6: Interior Wall Adjustments
Loadbearing Interior Walls
For interior loadbearing masonry walls, the strip footing width must be increased by 100 mm for every storey of masonry construction supported.
Non-Loadbearing Interior Walls
For non-loadbearing masonry, the minimum width is 200 mm for walls up to 5.5 m high. An additional 100 mm of width is required for every extra 2.7 m of height to ensure the slab or footing can distribute the dead load safely.
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.