Question 1

How big a hole can a plumber drill through my Ottawa joists?

Accepted Answer

Plumbing is out of scope here, but the carpentry rule on holes in joists is worth knowing because it is the same rule a carpenter or designer uses when any trade drills through framing. The 2024 Ontario Building Code (9.23.5.1.) says a hole in a floor, roof or ceiling framing member must be no more than one quarter of the member's depth, and the edge of the hole must be at least 50 mm from the top or bottom edge of the member. Both limits apply at the same time.

Question 2

Making a joist deeper to allow a bigger hole, is that allowed in Ontario?

Accepted Answer

The Ontario Building Code does allow increasing a joist's depth to compensate for a hole or notch, but the permission is tied to specific conditions, and the work still has to meet the Code's framing rules. For solid wood floor, roof and ceiling joists, the Code sets a hole limit of not more than one quarter of the joist's depth, placed at least 50 mm from the top and bottom edges (9.23.5.1.).

Question 3

Where along a joist is notching allowed in Ontario?

Accepted Answer

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.

Question 4

Cutting through a top plate for a duct in Ontario homes?

Accepted Answer

The Ontario Building Code (2024, O. Reg. 163/24) sets a clear limit for top plates: after notching or drilling, at least 50 mm of the plate's width must stay undamaged (clause 9.23.5.4.). That is the rule that governs what a carpenter can do when a duct has to pass through a plate. A top plate is part of the wall's load path, so how much can be removed matters.

Question 5

My HVAC installer cut a joist in my Kanata house, is that OK?

Accepted Answer

A cut joist is a structural concern that needs a carpenter or designer to look at in person before anything else happens. The Ontario Building Code (2024, O. Reg. 163/24) sets out what is and is not permitted when framing members are notched or drilled, and a joist that has been cut outside those limits needs to be assessed and likely repaired. For solid wood floor joists, clause 9.23.5.1.

Notching & Drilling

How big a hole can a plumber drill through my Ottawa joists?

Making a joist deeper to allow a bigger hole, is that allowed in Ontario?

Where along a joist is notching allowed in Ontario?

Cutting through a top plate for a duct in Ontario homes?

My HVAC installer cut a joist in my Kanata house, is that OK?