The 2024 Ontario Building Code — What Changed and What It Means for Your Renovation
The 2024 Ontario Building Code has been in full effect since April 1, 2025. It introduced over 2,000 changes from the previous code — most of them technical, but several with direct practical implications for residential renovations, secondary suites, and new construction in the GTA. If your project was designed before April 2025, the drawings may need to be updated before submission.
What Is the 2024 Ontario Building Code?
The Ontario Building Code (OBC) is the provincial regulation that sets minimum standards for the construction, renovation, and demolition of buildings in Ontario. It governs structural safety, fire protection, plumbing, energy efficiency, accessibility, and more. Every building permit application in Ontario must comply with the version of the OBC in effect at the time of submission.
The 2024 OBC adopted the framework of the National Building Code of Canada 2020 with Ontario-specific amendments. The previous version — Ontario Regulation 332/12 — had been in place since 2012 with periodic amendments. The transition to the 2024 code represents the most significant update to Ontario’s building standards in over a decade.
The 2024 OBC came into force on January 1, 2025, with a transition period for applications submitted before that date. As of April 1, 2025, all new permit applications must comply with the 2024 code. There are no exceptions for projects that were “already designed” under the old code — if the application has not been submitted, the drawings must meet the 2024 standard.
What Are the Key Changes That Affect Residential Renovations?
Minimum Ceiling Heights for Secondary Suites — 1.95 Metres Confirmed
The 2024 OBC establishes 1.95 metres as the minimum ceiling height in habitable rooms of secondary suites province-wide. This was previously subject to interpretation and varied in practice across municipalities. The 2024 code resolves the ambiguity — 1.95 metres is the standard, and it applies everywhere in Ontario.
For properties with basement ceiling heights below this threshold, the options are limited to underpinning (lowering the basement floor), benching (lowering portions of the floor), or redesigning the suite layout to exclude areas that do not meet the height requirement. There is no variance process for the OBC minimum ceiling height.
Updated Fire Safety Requirements
The January 2026 amendments to the Ontario Fire Code — which complement the 2024 OBC — introduced several changes relevant to residential construction:
Expanded CO detection requirements. Carbon monoxide alarms are now required adjacent to every sleeping area in a dwelling unit, not just on the floor level containing fuel-burning appliances. For multi-unit buildings including secondary suites, this means CO alarms in both the main unit and the secondary suite, positioned adjacent to sleeping areas in each.
Updated fire alarm standards. New interconnection requirements for smoke alarms in residential buildings with secondary suites. When a smoke alarm activates in one unit, all alarms in the building must sound. This requires hardwired interconnection or wireless interconnection systems that meet the updated standard.
Administrative penalties. The Fire Code amendments introduced a new administrative penalty regime for non-compliance — replacing the previous prosecution-only enforcement model with a more flexible penalty structure that applies even for first-time violations.
Energy Efficiency Requirements
The 2024 OBC adopts more stringent energy efficiency standards for new construction and additions. Changes affect insulation requirements, window performance, air barrier continuity, and mechanical ventilation. For additions and renovations, the requirements apply to the new construction — not necessarily to the existing building — but the line between what triggers upgraded requirements and what does not requires careful review.
Accessibility Provisions
Updates to accessibility requirements affect new construction and significant renovations in certain building classes. For most residential renovations, the accessibility provisions do not impose new requirements on the existing building. However, projects that trigger a “change of occupancy” or a renovation exceeding certain thresholds may be subject to updated accessible path of travel requirements.
What Does This Mean for Your Permit Application?
The practical implication for anyone submitting a permit application today is straightforward: all drawings must comply with the 2024 OBC. This includes projects that were designed, quoted, or partially started before April 2025.
If your drawings were prepared before January 2025, review them with your permit consultant before submission. The changes most likely to require updates are:
- ✓Ceiling height specifications in secondary suite drawings — must confirm 1.95m minimum
- ✓CO alarm placement — must comply with the January 2026 Fire Code update
- ✓Smoke alarm interconnection details in secondary suite applications
- ✓Insulation and vapour barrier specifications in additions — energy efficiency provisions
Municipal building examiners are actively reviewing applications for 2024 OBC compliance. Drawings that reference the old code or specify standards that no longer meet the current minimum will generate examiner comments. Updating drawings before submission is faster and cheaper than responding to comments after the fact.
What Does the 2024 OBC Mean for Basement Apartments Specifically?
Secondary suites are where the 2024 OBC changes have the most concentrated practical impact. The combination of the confirmed 1.95-metre ceiling height, the updated fire separation requirements, the new CO alarm placement rules, and the independent HVAC requirement means that a basement apartment designed to the 2012 code standard may fail on multiple counts under the 2024 code.
The most common issue is ceiling height. Many older GTA homes have basement ceiling heights of 1.8 to 1.85 metres — below the 2024 OBC minimum. Under the 2012 code, some municipalities accepted these heights with modifications or applied older local standards. Under the 2024 code, the 1.95-metre standard is province-wide and non-negotiable.
The second most common issue is independent HVAC. The 2024 OBC requires secondary suites to have independent ventilation systems separate from the primary dwelling unit. A finished basement that shares a furnace with the main house does not comply and will require a separate heating and ventilation solution as part of the permit scope.
How GTA Permits Handles the Transition
All drawings produced by GTA Permits are prepared to the current 2024 OBC. We track code updates as they occur and update our drawing templates and specifications accordingly. If a client brings us drawings prepared by another firm under the old code, we review them against the 2024 standard as part of our intake process and flag any updates required before submission.
For a full breakdown of what a compliant permit drawing package includes under the 2024 OBC, see our building permit drawings service page. For residential permit questions including secondary suites, see our residential permit services page. Common questions about the 2024 code are addressed in our FAQ.
Are Your Drawings 2024 OBC Compliant?
If your drawings were prepared before 2025, they may need to be updated. We review and update existing drawings or produce a new compliant package — whichever is faster for your timeline.
