What are the changes in the 2024 Ontario Building Code? Highlights 

Ontario announced a new 2024 Ontario Building Code (OBC). The changes prioritize public safety, housing affordability, sustainability, and climate resilience while streamlining processes for builders and municipalities. The new Building Code aligns with the National Building Code (NBC) while retaining provisions specific to Ontario’s needs, ensuring consistency across the province. The 2024 OBC has been effective since January 1, 2025.

Building Permit applications must be submitted using the 2024 Ontario Building Code.

2024 Ontario Building Code Change Highlights

The list below includes highlights and new requirements that may be applicable to your projects compared to the 2012 OBC version. Please note that this list is not a complete list of code changes. The Province of Ontario’s website provides the latest version of the 2024 Ontario Building Code

1) Changes for Houses

• New requirements for guards around windows

• Adjustments to nosing size in stairs

• New requirements for open stair risers

• Increased restrictions on opening sizes for stair guards

• Expanded requirements for carbon monoxide alarms

• New minimum separation distance requirements for exhaust outlets

• Minimum sump pit sizes

• General Review by a Professional Engineer required for all underpinning

2) Changes for Two-Unit Houses / Secondary Suites

• Smoke-tight barriers replace traditional fire separations

• Mandatory installation of interconnected smoke alarms

• Increased requirements for carbon monoxide alarms

• Lower ceiling heights and shared egress options

• Prohibited sharing of return air on purpose-built two-unit buildings

  • (Conversions of existing buildings can still share a furnace for up to four units under Part 11 of the Building Code)

• General Review by a Professional Engineer required for all underpinning

3) Changes About Carbon Monoxide Alarms

• Requirements expanded to more residential occupancies

• Added requirements for care occupancies and some commercial establishments

• Decibel level of audible signaling device added for smoke alarms

4) Changes About Radon Mitigation

• Harmonized with the NBC

• Mandatory rough-in for subfloor depressurization in all new homes

• SB-9 revised with prescriptive requirements for rough-ins

5) Changes to Wood Frame Construction

• New connections to preservative-treated wood

• Updated fastening and anchorage requirements

• Increased seismic and high-wind area considerations

• New provisions for:

  • Rafters

  • Ceiling joists

  • Braced wall panels

• Updated rafter-to-joist nailing chart with new spacings and increased nailing requirements

6) Changes to ICF Foundation Systems

• Insulated Concrete Form (ICF) foundation walls now permitted for buildings up to:

  • Two storeys

  • Maximum floor-to-floor height of 3000 mm (10 ft.)

7) Changes to Cladding

• New requirements for attaching siding to ICF forms and sheathing

• Insulated vinyl siding now permitted

• Polypropylene siding now permitted

• New subsection added for polypropylene siding

8) Changes About Structural Design (Part 4)

Harmonized with the National Building Code in the following areas:

• Importance categories — revised descriptions

• Solar panels — new provisions to calculate wind and snow loads

• Canopies and parapets — new wind load calculations for:

  • Attached canopies

  • Roof parapets

  • Balcony guards at top of buildings

• Earthquake design updates

• General Review by a Professional Engineer required for all underpinning

9) Changes About Heating & Ventilation (Part 6)

• Each dwelling unit must have its own thermostat for independent control

• Subsection 6.2.4 (Air Ducts for Low Capacity Systems in OBC 2012) moved to Section 9.33 Heating and Air-Conditioning

• Section 9.32 Ventilation harmonized with NBC

  • Removal of ventilation Types I to IV

• Ventilation of storage and repair garages harmonized

  • (except carbon monoxide requirements in repair garages)

10) Changes About Plumbing (Part 7)

• Greater flexibility and more material choices

• Improved health and safety requirements

  • Maximum temperature reduced from 49°C to 43°C in healthcare and senior facilities

• Clarification of technical requirements for:

  • Shower heads

  • Domestic water tanks

  • Grease interceptors

• Standardization of non-potable water systems:

  • Rainwater harvesting

  • Greywater reuse

11) Changes for Septic Systems (Ontario-Only Changes) (Part 8)

• Increased safety requirements for:

  • Septic tanks

  • Treatment units

  • Holding tanks

• New standards for prefabricated septic and sewage holding tanks

  • Includes safety screen below cleanout covers

• Revised spacing requirements for pipes and chambers

  • Ensures even effluent distribution in filter beds

• Clarified materials for the Type A Dispersal Bed mantle

Note: Additional articles will be released to provide detailed explanations of major changes and new requirements in the 2024 OBC.