Where along a joist is notching allowed in Ontario?

The 2024 Ontario Building Code (O. Reg. 163/24, clause 9.23.5.2.) permits notches on the top of a joist only, and only within half the joist's depth of a bearing point. The notch cannot be deeper than one third of the joist's depth, unless the member's depth is increased to compensate.

A few related rules from the same section are worth knowing alongside that one:

• Holes drilled through a joist cannot exceed one quarter of the joist's depth, and must sit at least 50 mm from any edge (9.23.5.1.).
• A load-bearing stud keeps at least two thirds of its depth after notching or drilling; a non-load-bearing stud keeps at least 40 mm, unless the stud is reinforced (9.23.5.3.).
• A top plate keeps at least 50 mm of its width undamaged after notching or drilling (9.23.5.4.).
• A truss member is not cut or notched at all unless the truss design expressly allows it (9.23.5.5.).

One important exception: we found no notching or drilling limit in clause 9.23.5. for engineered I-joists or LVL members. Ask your designer before anything is cut into an engineered member.

"Structural repairs or alterations" appear on the City of Ottawa's permit list at ottawa.ca, so if a notch has already been cut and you are repairing the framing, confirm with the City whether a permit is needed before work begins.

The request form on this page goes directly to Ottawa carpenters listed in the Ottawa Construction Network directory, if you want someone to look at the framing in person.