Fire Separation Requirements for Commercial Buildings in Ontario

Fire separation is one of the most common code requirements that affects commercial renovation projects in Ontario. If you are building demising walls between tenants, creating a kitchen in a restaurant, or converting a space from one use to another, fire separation rules will almost certainly apply to your project.

What Is a Fire Separation

A fire separation is a construction assembly (wall, floor, or ceiling) that is designed to resist the passage of fire for a specified period of time. In the Ontario Building Code (OBC), fire separations are rated in hours: 30 minutes, 45 minutes, 1 hour, 1.5 hours, or 2 hours.

The rating indicates how long the assembly can withstand fire exposure while maintaining its structural integrity and preventing flame passage.

Common Fire Separation Requirements in Commercial Renovations

Demising Walls Between Tenants

When two commercial tenants share a building, the wall between their spaces is a demising wall and must be a fire separation. For most Group D (business and personal services) occupancies, the OBC requires a minimum 1-hour fire separation between tenants.

This wall must extend from the floor slab to the underside of the structural deck above, not just to the ceiling grid. Stopping a demising wall at the drop ceiling is one of the most common code violations in commercial renovations.

Corridors and Exit Paths

Corridors that serve as exit paths in multi-tenant buildings require fire separations. The typical requirement is 30 minutes to 1 hour depending on the building height and occupancy type.

Kitchen Exhaust and Cooking Areas

Restaurant kitchens with commercial cooking equipment require fire separations between the kitchen and dining areas. The requirement depends on the hood type and whether the space has a sprinkler system.

Electrical and Mechanical Rooms

Electrical rooms, mechanical rooms, and service rooms that penetrate fire separations require fire-rated enclosures and fire-stopped penetrations.

Change of Use

If you are converting a space from one OBC occupancy group to another (for example, Group D office to Group A assembly, or Group D office to Group B clinical), the fire separation requirements of the new occupancy apply. This can trigger significant upgrades to existing walls, ceilings, and penetrations.

What a Fire-Rated Wall Assembly Looks Like

A 1-hour fire-rated wall in a commercial renovation typically consists of:

• Steel studs at 16" or 24" on centre
• One or two layers of 5/8" Type X gypsum board on each side (depending on the tested assembly)
• Mineral wool insulation in the cavity
• Fire caulking at all penetrations (electrical boxes, pipes, ducts)
• Fire dampers at all HVAC duct penetrations
• Fire-rated door assemblies at all openings

The specific assembly must match a tested and listed configuration from a recognized testing authority (ULC in Canada).

Fire Stopping

Every penetration through a fire separation must be fire-stopped. This includes:

• Electrical conduit and cable trays
• Plumbing pipes
• HVAC ducts (require fire dampers)
• Data cabling
• Any sleeve or opening

Fire stopping must be done with tested and listed products applied according to the manufacturer's installation instructions. Stuffing mineral wool into a hole or applying generic caulking does not meet code.

How This Affects Your Renovation Budget

Fire separation work typically adds $8-20 per linear foot of rated wall, depending on the rating requirement and the number of penetrations. A 3,000 sq ft office renovation with 80 linear feet of demising wall at 1-hour rating will add roughly $2,000-4,000 for the wall assembly and fire stopping.

Change-of-use projects can be significantly more expensive because existing walls and penetrations must be upgraded or replaced to meet the new occupancy requirements.

The Inspection Process

Fire separations are inspected by the municipal building department at the framing stage (before drywall is closed) and again at the final inspection. Fire stopping is typically inspected as part of the rough-in inspection. Failed inspections require correction before the project can proceed.

VNG builds fire-rated assemblies to code on every project and coordinates all inspections with the building department. Contact us to discuss your renovation scope and permit requirements.