Ontario replaced its building code. The 2024 Ontario Building Code came into force on January 1, 2025, and after a short transition period, every new permit application in the province has run under it since April 1, 2025. If you are planning a renovation, an addition, or a basement suite, this is the rulebook your project will be inspected against — whether your contractor knows it or not.
This was not a small update. Ontario harmonized its code with the National Building Code of Canada and removed roughly 1,730 Ontario-only variations. Clause numbers moved, requirements changed, and some things that passed inspection for years don't pass anymore.
Here are the five changes that matter most for homeowners.
1. Your renovation pulls the new code in with it
Cosmetic work — paint, flooring, swapping a toilet like for like — usually doesn't trigger the code. But the moment your project touches structure, exits, fire separation, or mechanical systems, the current code applies to that work.
That catches people off guard. Open a wall, move a stair, add a door, finish a basement — and the new rules come with it. A quote that doesn't account for that is a quote that's going to grow.
2. Side walls have a limit on windows and doors
This one decided a real design on a job I am working on right now in Barrie.
The code measures the distance from your wall to the property line — called the limiting distance — and caps how much of that wall can be windows and doors. On a side wall roughly 6'11" from the lot line, the cap is 9% of the wall area. Get closer to the line and the cap gets tighter.
For a new basement side entrance, that meant the door had to be a solid, unglazed door to stay inside the limit. A door with a big window in it — the one most people would pick off the shelf — would have failed. This is the kind of thing that has to be caught at the design stage, not at inspection.
3. Stairs and guards have hard numbers
If your project involves stairs, the 2024 code sets the measurements:
- Rise: maximum 7 7/8 inches per step
- Run: minimum 8 1/4 inches per step
- Headroom: minimum 6'5" over the stair
- Guards: required where the drop beside a landing or deck exceeds 2 feet
Keeping an existing stair? It still gets checked against these numbers when it's part of the permitted work. Plenty of older stairs in Barrie houses were built steeper than this — and "it's always been like that" is not an argument an inspector accepts.
4. New homes need radon rough-ins and real ventilation
Two changes hit new construction and additions hardest:
- Radon: A sub-floor depressurization rough-in is now required in new homes. It's a pipe and a provision so a radon fan can be added later if testing shows it's needed. It costs very little while the foundation is open and a lot afterward.
- Ventilation and energy: The code now ties the building envelope to the mechanical systems. A tighter, better-insulated house has to be ventilated on purpose, which means a heat or energy recovery ventilator (HRV/ERV) is effectively part of every new home build — and the energy choices get locked in at design, not halfway through the build.
5. Basement suites got more flexible — and more specific
The 2024 code updated the rules for secondary suites to support more housing. Ceiling height flexibility that used to apply only to older homes now extends further — suites can go as low as 6'-5" in cases where the old code said no. Carbon monoxide alarm requirements were also adjusted, especially in multi-unit setups.
That doesn't make a legal suite simple. Egress windows, fire separation, and alarms all still have to be right. It just means some basements that couldn't legally become suites under the old code can now.
I wrote a full breakdown of what makes a basement suite legal in Barrie here: https://conceptsconstruction.ca/blog/legal-basement-suites-in-barrie-egress-permits-and-what-makes-a-suite-legal/
6. Additions carry an energy price tag
When you add onto your house, the new part has to meet the current energy requirements — even though the rest of the house stays exactly as it is. Insulation levels, a continuous air barrier, and windows that perform to today's standard, all picked at the design stage under the code's energy rules.
This is where quotes split apart. Two contractors can price the same addition and land thousands of dollars apart because one included the energy package and the other quietly left it out. The one who left it out isn't cheaper. He's just handing you the difference later — or leaving you to argue with the inspector.
Ask any contractor these three questions
- Is this priced to the 2024 code? If the answer is a blank look, you have your answer.
- Who's doing the drawings? Permit drawings come from a qualified designer, and structural work needs an engineer's stamp. "We'll figure it out at the permit office" is not a plan.
- Is the energy package in the number? Insulation, air barrier, windows. If it's not in the quote, it's in the change order.
The bottom line
The building code is not paperwork. It decides what your door can look like, how steep your stairs can be, and whether your basement can legally be a suite. When a contractor prices your job off the old book, you pay for the difference later — in change orders, failed inspections, or work that has to be redone.
Get the design right first, and the permit follows.
Planning a renovation in Barrie or Simcoe County? Get a free estimate: https://conceptsconstruction.ca — or book a time that works for you: https://calendly.com/conceptsinc/construction-estimate-service
Free Estimates. Honest Solutions.
— Mark Johnston, Concepts Construction, (705) 330-2911
