What is a fire rated door?
A fire rated door is part of a tested assembly designed to slow the spread of fire and smoke through a wall opening. The rating (20, 45, 60, 90, or 180 minutes) describes how long the assembly is expected to perform under standard test conditions.
It is not just the door slab. A compliant assembly typically includes the frame, hinges, latch, closer, seals, and correct clearances – all tested and installed together.
Are fire rated jambs mandatory in Ontario?
Usually yes – when the Ontario Building Code (OBC) requires a fire rated door, the frame and jambs must be part of a compliant closure assembly. You cannot install a rated door slab in a standard interior frame and assume it passes inspection.
The OBC treats a closure as the full opening protectives system: door, frame, hardware, closing devices, and anchors – not the slab alone.
Exception (Part 9, 20-minute only): For certain low-rating residential situations, OBC Articles 9.10.13.2 and 9.10.13.3 allow a 45 mm solid-core wood door (CAN/ULC-S113) in an unrated wood frame that is at least 38 mm thick. This does not apply to 45-minute or higher ratings.
When does Ontario require a fire rated door?
Requirements depend on building type, occupancy, and the fire separation. Common examples include:
- Door between an attached garage and the house
- Stairwell and exit corridor openings
- Certain utility and mechanical rooms
- Multi-unit residential fire separations
Your local building department (Authority Having Jurisdiction) determines what applies to your project.
Does the frame rating have to match the door?
Yes. The door and frame must be part of the same listed, tested assembly unless a specific OBC exception applies (such as the 20-minute Part 9 wood door path above).
Steel frames in fire separations must conform to CAN/ULC-S105. Full assemblies are tested to CAN/ULC-S104 and installed per NFPA 80.
What are the most common inspection failures?
- Gaps out of tolerance – typically 2-4 mm at head and jambs; threshold gaps only within what the listing allows
- Door does not self-close and latch – missing, broken, or weak closers; doors propped open
- Missing or damaged seals – intumescent strips cut short, painted over, or absent
- Wrong hardware – non-listed hinges, closers, or latches substituted in the field
- Missing or illegible labels – no way to verify the assembly rating
- Unauthorized modifications – trimming the door, extra viewers, or field changes not approved by the manufacturer
A door that cannot self-latch is effectively not a fire door, regardless of its label.
What gap clearances should I expect?
| Location | Typical tolerance |
|---|---|
| Head and side jambs | 2-4 mm (often 3 mm nominal) |
| Threshold / floor | Up to 8 mm with correct seal (varies by listing) |
| OBC 20-min wood door path | Max 3 mm sides/top, 6 mm bottom |
Always follow the manufacturer listing and test evidence for your specific door assembly. Generic rules are a starting point, not a substitute for the label.
Can I replace just the door and keep the old frame?
Only if the existing frame is part of the same listed assembly and remains in compliant condition. In practice, slab-only swaps often fail inspection because the frame, hardware, and seals do not match the new door’s certification.
For rated openings, treat door + frame + hardware as one system. Replace as a matched assembly when in doubt.
Quick reference: Ontario frame requirements
| Situation | Fire rated frame/jambs required? |
|---|---|
| 20-min Part 9 wood door (9.10.13.2 / 9.10.13.3) | Unrated 38 mm wood frame permitted |
| 45-min or higher rating | Yes – listed assembly required |
| Stairwell / exit / commercial Part 3 | Yes – full CAN/ULC-S104 assembly |
| Steel frame in fire separation | Must meet CAN/ULC-S105 |
Who has the final say?
Your local building department (AHJ) interprets and enforces the OBC for your specific project. This FAQ is general guidance, not legal or engineering advice. Confirm ratings, locations, and assembly requirements with your inspector or a qualified fire door professional before ordering or installing.
