OBC 9.9.10 Egress Window Requirements Toronto Explained

# OBC 9.9.10 Egress Window Requirements Toronto Explained

Ontario Building Code Section 9.9.10 is the spine of every legal basement bedroom and apartment in the province. The rules are short — fewer than two pages of code — but the consequences are large. A basement room without a 9.9.10-compliant window is not a bedroom. A basement apartment without 9.9.10 windows in every sleeping room cannot be registered with the City of Toronto. An insurance claim for a fire injury in a non-compliant basement bedroom will be denied or reduced. Every Toronto homeowner planning a finished basement, a legal apartment, or a multiplex conversion needs to understand 9.9.10 before construction starts, not after.

This article walks through the four dimensional rules, the operability rules, the window well rules, and the practical interpretations Toronto building inspectors apply in 2026. For the full project framework including cost and permit pathway, see our [Egress Window Installation Toronto: Complete 2026 Guide](/blog/egress-window-installation-toronto-2026-complete-guide). For the legal-bedroom-specific angle, see [Egress Window for Basement Bedroom Legal](/blog/egress-window-for-basement-bedroom-legal). For the fire-code logic that drives the whole specification, see [Egress Window Fire Code Explained Toronto](/blog/egress-window-fire-code-explained-toronto).

What 9.9.10 Actually Says

OBC 9.9.10 covers "egress windows or doors for bedrooms." Every bedroom in a single dwelling unit, every bedroom in a secondary suite, and every sleeping room in a registered basement apartment must have at least one outside window or exterior door that meets the section's requirements. The window or door is the second means of egress (the first being the bedroom door to the interior corridor); both must remain functional simultaneously, which is why a bedroom with a single window and a door that locks from outside fails the test.

The rules apply identically regardless of whether the bedroom is above grade, at grade, or below grade. The only thing below-grade bedrooms add is the window well requirement, which exists because the window itself cannot be the egress if the window opens into a pit too small to climb out of.

Rule 1: Minimum Unobstructed Openable Area — 0.35 sq m

The opening through the window, measured when the operable sash is fully open, must be at least 0.35 square metres (3.77 square feet, or 543 square inches). "Unobstructed" means the dimension is measured through the actual clear opening, not the rough opening or the frame size. Hinges, sash hardware, and any operating mechanism reduce the clear opening; the measurement is what's left.

A casement window with a 36-inch wide frame and a 48-inch tall sash that opens to 90 degrees produces a clear opening roughly 30 inches wide by 44 inches tall — about 0.85 square metres. Comfortably above the minimum. A slider with the same frame dimensions opens only on one half — clear opening is roughly 17 inches by 44 inches, or 0.48 square metres. Still above the minimum on a 36 × 48 frame, but very tight if the frame is smaller. A small basement-original window with a 24-inch wide by 16-inch tall sash produces a clear opening of about 0.25 square metres at best — below the minimum, fails the test.

The 0.35 sq m rule is the size test most homeowners hear about first. It is not the only rule and it is not even the most commonly failed rule in Toronto inspections — that distinction belongs to the sill-height rule below.

Rule 2: Minimum Dimension in Any Direction — 380 mm

The opening must be at least 380 millimetres (15 inches) in both height and width through the open sash. This rule prevents a tall narrow opening from satisfying the area rule on paper while being un-traversable in practice. A 200 mm × 1750 mm opening is 0.35 square metres but no firefighter in SCBA gear gets through 200 mm, so the rule fails.

In Toronto inspections we see this rule most often as a check on slider windows. A slider with a tall narrow openable half can hit 0.35 sq m of area while the openable width is only 350 mm. Inspector fails the install. Casements rarely fail this rule because casement geometry naturally produces wider openings.

Rule 3: Maximum Sill Height — 1.0 m Above Finished Floor

The sill of the openable portion must be no more than 1.0 metre (39.4 inches) above the finished floor inside the bedroom. This is the rule most often failed in Toronto basement retrofits. Reason: when basements are lowered through underpinning or bench footing, the new finished floor sits 12 to 24 inches below the old floor, but the original window sill stays where it was. A window that used to sit 90 cm above the old floor now sits 110 to 130 cm above the new lower floor — non-compliant.

The fix has two paths. Path one: cut the foundation lower so the new sill drops to within 1.0 m of the new finished floor. Path two: build a permanent step or platform inside the bedroom so the effective floor at the window is raised — but this only works if the platform is built to permanent-construction standards (not removable steps) and the inspector accepts it. In our experience the inspector rarely accepts the platform approach for a sleeping room. Cutting the foundation is the reliable fix.

Rule 4: Operability Without Tools

The window must open from the inside without keys, tools, or special knowledge. A standard casement crank, a slider thumb-latch, or a lift-out sash all qualify. Disqualifying mechanisms include:

• Security bars without an interior quick-release.
• Window air conditioners that block the openable area.
• Storm windows that require disassembly to clear the opening.
• Painted-shut sashes that require a knife to free.
• Hardware that has failed and no longer holds the sash open against gravity.

The operability test is performed in real time during inspection. The inspector will open and close the window. A sticky casement that requires shoulder pressure passes if it does eventually open; a crank with a stripped gear that won't operate at all fails.

Window Well Rules

When the window is below grade, the window well becomes part of the egress system. OBC and Toronto best-practice rules:

• Horizontal projection: the well must extend at least 550 mm (22 inches) outward from the foundation face. We typically install 750 mm to give a more usable space.
• Width: the well must be at least the window width plus modest clearance on each side; standard well sizes from manufacturers like Boman Kemp accommodate the typical 36 to 60 inch egress window widths.
• Depth and ladder requirement: if the depth from grade to the bottom of the well exceeds 1.0 metre, a permanent ladder or steps are required. The ladder must be permanently affixed and rated to support an adult.
• Drainage: the bottom of the well must drain. A well full of standing water is not an egress.
• Cover: if the well has a cover, the cover must be openable from inside the well. Screwed-down decking is not compliant.

For a full window well design walkthrough, see [Window Well Drainage Toronto Design](/blog/window-well-drainage-toronto-design).

Bars, Grilles, and Security

Many Toronto basement windows have security bars installed by previous owners. These are permitted by OBC only if the bars include an interior quick-release that does not require keys, tools, or special knowledge, and the released bars allow the full required opening. In practice, almost all retrofitted security bars on Toronto basement windows fail this test. They are bolted from the outside, have no interior release, or have a release that uses a wing nut (which counts as a tool in some inspectors' interpretation).

The fix on a bedroom window is to remove the bars entirely. Security in a basement bedroom is provided by the window itself — modern egress windows come with multi-point locking hardware that resists forced entry while still being releasable from inside without tools.

How Toronto Inspectors Apply 9.9.10

Toronto Building inspectors apply 9.9.10 in 2026 with a few practical tendencies:

• They measure. Tape measures come out for height, width, sill, and well dimensions. Don't assume "close enough" passes.
• They test the operation. They open the window themselves, fully, and observe whether the hardware holds it open.
• They check the well. Cover lift, ladder presence if depth requires, drainage condition.
• They check the smoke alarm. A bedroom requires a smoke alarm wired and inspected — not strictly part of 9.9.10 but inspected at the same visit on basement-apartment legalizations.
• They check the secondary exit overall. On a basement apartment, the second exit (separate door to grade or shared stair) is checked alongside the bedroom egress. Both must be functional.

Inspectors are not adversarial. They want the install to pass. The most common reason a Toronto egress install fails first inspection in our experience is a cosmetic issue (trim not finished, drywall not complete) or a missing smoke alarm — not a 9.9.10 dimensional issue, because we measure during install and we know the rules. Homeowner-managed installs without permits frequently fail dimensional rules on first inspection.

What 9.9.10 Does Not Cover

Worth noting what is outside 9.9.10's scope:

• Energy code (SB-12): The window itself must meet Ontario energy efficiency requirements separately. Most modern egress windows do.
• Fire separation: Between the basement apartment and the upstairs unit, fire separation is OBC 9.10, not 9.9.10. Different rules.
• Smoke and CO alarms: OBC 9.10 and Ontario Fire Code, not 9.9.10.
• Ventilation: OBC 9.32. The egress window can satisfy ventilation requirements as a side benefit, but that is a separate rule.

A complete legal basement bedroom or apartment satisfies all of these in addition to 9.9.10.

Common Misconceptions

A few myths we hear from Toronto homeowners:

• "My basement window is original, so it's grandfathered." Not for habitable bedroom use. Grandfathering applies to non-habitable use; the moment you call the room a bedroom, current code applies.
• "The window is huge so it's compliant." Maybe. Check the openable area, not the frame size. A picture window with a small operable transom can fail.
• "I don't need a permit if I just replace the window with a bigger one." Yes you do — enlarging the foundation opening triggers a structural permit.
• "Window wells are optional." Not below grade. They are part of the egress.
• "My inspector won't actually measure." They will.

For the full project framework around 9.9.10, see our [Egress Window Installation Toronto: Complete 2026 Guide](/blog/egress-window-installation-toronto-2026-complete-guide). For the cost framework, see [Egress Window Cost Toronto Installation](/blog/egress-window-cost-toronto-installation). For the foundation cutting that brings most below-grade installs into compliance, see [Egress Window Foundation Cutting Toronto](/blog/egress-window-foundation-cutting-toronto).

Ready for an OBC-Compliant Install

If you are unsure whether your existing basement windows meet 9.9.10, the right starting point is a site visit. We will measure each window, the sill heights, the well dimensions if any, and the operability of the existing hardware, and we will tell you in writing which windows are compliant and which need work.

[Book an egress window consultation](/services/home-renovation/egress-window-installation) to start the conversation.