Ontario Building Code 2024: What Changed and What It Means for Your Permit

The Code Changed — and Your Drawings Have to Match

Since April 1, 2025, the 2024 Ontario Building Code has been the in-force edition for all new permit applications. The transition window closed on March 31, 2025, which means drawing sets prepared under the previous edition are no longer accepted on their own.

This matters more than a typical code update because several of the changes land directly on the drawings a municipality reviews — not on construction practice, but on the document set. A permit set that doesn't reflect the current requirements gets a deficiency notice, and the review clock restarts.

The Changes That Show Up on Permit Drawings

These are the 2024 OBC changes we see affecting residential and small commercial permit submissions most often:

Part 9 vs Part 3 — Still the First Question

The 2024 edition did not change the fundamental split between Part 9 (houses and small buildings) and Part 3 (larger and more complex buildings), but it's the first thing that determines which requirements apply to you — and misclassifying it is one of the most common reasons a submission stalls.

Broadly: a detached house, a small addition, and a modest commercial fit-out generally fall under Part 9. Larger commercial, industrial, multi-residential, and assembly occupancies fall under Part 3, which brings a substantially deeper set of requirements — including fire separations, exiting, and often the involvement of additional consultants.

Submitting a Part 9-style drawing set for what is actually a Part 3 project is a guaranteed deficiency. It's worth confirming the classification before the drawings are started, not after.

What This Means If You Have Older Drawings

If you have a drawing set from 2024 or earlier and you're planning to submit it now, it won't clear review as-is. The specifics that usually need updating:

• The energy compliance form — regenerate it against the current SB-12 requirements with your actual assembly values.
• Radon provisions — add the sub-floor depressurization rough-in to the foundation and floor plans if it isn't shown.
• CO alarm locations — update the life-safety notes to the expanded trigger.
• Suite separation details — if the project includes a secondary suite, confirm the smoke-tight barrier is detailed, not just noted.
• The code reference block — the title block and general notes should cite the 2024 edition.

In many cases updating an existing set is far cheaper than redrawing from scratch — but it does need to be done deliberately, requirement by requirement. Our post on common permit drawing mistakes covers where these typically get missed.

Timing: Why Fall Submissions Still Make Sense

The code change doesn't alter the seasonal pattern of permit review. Municipal building departments process applications continuously, but intake volume peaks in late winter and early spring when everyone wants to break ground for summer. Submissions in October and November generally move through review faster.

That's an argument for starting the code-compliance update on your drawings now rather than in March — see our breakdown of Ontario permit timelines for the project-by-project ranges.

Code Compliance Across the GTA

While the Building Code is provincial, municipal review practice and local requirements vary. Find your city:

May Engineering Inc: Drawings That Meet the 2024 Code

May Engineering Inc prepares permit drawing sets to current Ontario Building Code requirements — architectural, structural, energy compliance, and life safety coordinated in one submission. We work to the 2024 edition as a matter of course, including radon provisions, expanded CO alarm requirements, and suite separation detailing where applicable.

Working from an older drawing set, or starting fresh? Send us what you have and we'll tell you what needs updating before it goes to the municipality.