Ontario Fire Code Basics
for Home Renovations

In a house with one secondary suite, Ontario's 2024 Building Code does not require a rated fire separation between the two units if the walls and floor-ceiling framing are covered by a continuous smoke-tight barrier of 15.9 mm (5/8 inch) Type X gypsum board (Division B, Article 9.10.9.16).

That exception has applied since 2025-01-01 and covers exactly two units. Add a third, and the Code's general rules for separating dwelling units, described below, apply.

The first inspection that fails most Ottawa basement renovations is not framing or plumbing. It is the fire inspection. The reason is almost always the same: a contractor wrapped the project in regular drywall and called it done, and the inspector pulled out the code book.

The Ontario Building Code Section 9.10 is the part of the code that deals with fire protection in houses and small buildings. It is dense, but the parts you actually run into during a residential renovation are knowable. After 20 years on Ottawa job sites, here is what you need to understand before the framers show up.

This is not legal advice. It is what your inspector will be checking, and what your BCIN designer has to specify on the drawings before the City stamps the permit.

What "Fire Separation" Actually Means

OBC Section 9.10.9 defines a fire separation as a construction assembly that resists the spread of fire from one space to another for a defined period of time, measured in minutes or hours.

The most common rating in residential work is the 45-minute fire separation. A typical assembly that achieves this is one layer of 12.7 mm Type X drywall on each side of standard wood-stud framing, with mineral wool or fibreglass insulation in the cavity, and all joints taped and mudded. Sounds simple. It is not, because the rating only counts if every penetration is also rated.

For higher-risk situations, the code calls for a 1-hour fire-rated assembly. That is two layers of Type X drywall on at least one face, or a single layer over resilient channels with a code-listed assembly behind it. This is the rating you hit between dwelling units in a duplex or between a legal basement suite and the upstairs.

Fire Separation Between Dwelling Units

OBC 9.10.9.14 requires a fire separation between every dwelling unit and the rest of the building. In Ottawa, this matters most when you are creating a secondary dwelling unit, a basement apartment, or any kind of duplex conversion.

The rule is straightforward in concept:

• Walls and floors separating dwelling units must be a 45-minute fire separation, minimum.
• If you do not have a sprinkler system, the rating goes up to 1-hour in many cases.
• The fire separation has to be continuous. No gaps, no breaks, no shortcuts at the perimeter.

The continuous part is what trips most projects. A wall that ends at a dropped ceiling, or stops short of the joist above, is not a fire separation. It is just a wall. The drywall has to run tight to the structural deck, and any service penetration through that line has to be sealed with code-listed firestop products.

The 2024 Code's Exception for a House With a Secondary Suite

The Ministry of Municipal Affairs and Housing set out the change in its August 2024 briefing on Part 9. The exception rests on the Code's new definition of a secondary suite (Division A, Article 1.4.1.2), explained in our guide to secondary dwelling units in Ottawa, and Ontario put no size limit on the suite.

The national model code accepts a thinner 12.7 mm barrier but caps the suite's size; Ontario left the size open and asked for 15.9 mm Type X.

For a basement apartment in an Ottawa house, the floor-ceiling framing between the units is the basement ceiling, so the barrier runs across it in one continuous layer and down any walls the units share. The barrier has to be continuous, so a gap around a drain stack or an unsealed pot light breaks it, and every penetration gets sealed.

The same briefing lists two more fire changes for a two-unit house:

• Exterior walls that meet at an external angle of 135 degrees or less can be finished inside with 15.9 mm Type X when the walls between the units are not built as fire separations (Article 9.10.12.3).
• Smoke alarms in the two units can be interconnected wirelessly (Sentence 9.10.19.5.(2)), useful when each unit has its own electrical service.

Source: Ontario Ministry of Municipal Affairs and Housing, 2024 Edition of Ontario's Building Code, Part 9 housing and small buildings, read 2026-10-05.

Smoke Alarms and Interconnection: OBC 9.10.19

This is the section that catches the most homeowners off guard, because the rules changed and a 1990s house almost never meets the current standard.

What the current Ontario Building Code requires for smoke alarms in a renovated house:

• Hardwired to the electrical system, with a battery backup
• One on every storey, including the basement
• One inside every bedroom
• One in the hallway outside the bedrooms
• All smoke alarms interconnected, so when any one goes off, every alarm in the house goes off

The interconnection requirement is the part that surprises people. It can be hardwired (a third conductor running between alarms) or it can be wireless (radio-frequency models that talk to each other). Either is allowed, but they have to all be the same brand and model family, because manufacturers do not cross-talk.

Carbon monoxide alarms are also required if the home has any fuel-burning appliance or an attached garage, per OBC 9.32.3.9. They go in any room where someone sleeps and adjacent to fuel-burning equipment.

Sprinklers in Legal Suites

Most Ottawa homeowners hear "sprinkler" and assume it does not apply to a house. In a single-family detached, that is right. The minute you add a second dwelling unit, the rules change.

OBC 9.10.19.4 and the related sections allow a tradeoff: if you sprinkler the suite to residential standards, you can drop the wall and floor separations from 1-hour back to 45 minutes, you can use simpler egress, and you sometimes get relief on stair widths and ceiling heights.

For a typical Ottawa basement legalization, the homeowner has two paths:

1. Build to 1-hour separation, no sprinkler. Cheaper materials, but the assembly is fussier and the headroom takes a hit because you are adding drywall layers.
2. Build to 45-minute separation, with residential sprinklers. Higher upfront for the sprinkler install, but the construction and inspection are easier, and resale appeal is real.

Which path is right is a project-by-project call. We sit down with the basement layout and run both numbers before recommending one.

"The fire code is not there to make life difficult. It is there because in 1980 a basement apartment fire in Toronto killed seven people, and the code rewrote itself afterward."

Fire-Stopping at Penetrations

Every wire, pipe, duct, and stack that passes through a fire separation creates a hole. Each hole has to be filled with a listed firestop assembly, and the assembly has to match what is going through it.

What that means in practice:

• Plumbing stacks (cast iron or ABS): intumescent collars rated to the assembly's hours
• Electrical wiring: red firestop putty pads or sealant around boxes and cable openings
• Ductwork: fire dampers in any duct crossing a separation, listed and labelled
• Recessed pot lights: rated as IC-AT or covered with a fire-rated tent above; standard pot lights are not allowed in a fire-rated ceiling
• Existing penetrations: if your renovation touches the assembly, the inspector can require you to fix non-compliant existing penetrations as part of the permit

Every product must be a tested assembly with a ULC listing number. Spray foam from a can is not a firestop. Caulking is not a firestop. Drywall mud is not a firestop. The inspector knows the listed products and looks for them by part number.

Egress: The Other Half of Fire Code

Section 9.9 of the code covers means of egress and pairs with the fire-separation rules. Every habitable room, especially bedrooms, must have a way out that does not depend on going through another bedroom.

For Ottawa basement bedrooms, that means an egress window:

• Minimum opening of 0.35 m² (3.77 sq ft)
• No dimension less than 380 mm (15 inches)
• Sill height max 1.5 m (59 inches) above the floor
• Window well outside, with at least 760 mm clear in front of the opening

If your existing basement has 24 x 24 inch hopper windows, none of them qualify. You will be cutting concrete and installing a new larger window plus a properly drained window well. Plan a per-window line item for this in Ottawa; concrete cutting, the larger unit, and the drained well are the cost drivers.

Inspection Stages You Should Plan For

The City of Ottawa inspectors will visit at multiple stages. The fire-related stops are usually:

1. Framing inspection. Walls are up, before insulation. The inspector verifies stud spacing, fire-block locations, and any structural items.
2. Insulation inspection. Insulation in, vapour barrier in, before drywall. This is also when fire-stopping at top and bottom plates is checked.
3. Drywall inspection. First layer of drywall up, joints visible, before tape and mud. The inspector confirms the right type and thickness, and that fasteners hit the schedule.
4. Final inspection. Smoke alarms tested, interconnection confirmed, fire dampers labelled and operational.

Skipping the drywall inspection because "it slows the project down" is the single most expensive mistake homeowners let their contractor make. If the inspector finds an issue at final, the drywall is coming down.

Why This Matters Beyond the Permit

Two reasons every Ottawa homeowner should care about Section 9.10 even if their contractor is handling it.

First, your insurance company will deny a fire claim on illegal or non-compliant work. We have seen claims rejected on legal suites that were built without permit, and on basement renos where the smoke alarms were never interconnected.

Second, when you sell, the buyer's lawyer will ask for permits and final inspection certificates. Open or non-existent permits get flagged in the closing documents, and the deal either gets re-priced or falls apart.

Building to OBC 9.10 is not just a regulatory hurdle. It is the documentation that protects the value of your home for the next 30 years. If you have questions about a specific project, call 613-862-4555 for a free 48-hour feasibility review on your lot, or learn more about the full Ottawa permit process.

Frequently asked questions

Official references

• Do I need a building permit?, City of Ottawa