Egress Window Requirements Ontario: Sizes, Specs & What Inspectors Actually Measure in 2026

If you’re finishing a basement, adding a bedroom below grade, or building a secondary suite, egress windows are one of the first things your building inspector will check — and one of the most common reasons projects get red-tagged. The concept is simple: if a fire blocks the interior stairs, people sleeping in the basement need a way out that doesn’t involve prayer and improvisation. The Ontario Building Code takes this seriously, and so should you.

The frustrating part? The requirements are straightforward once you know them. But most homeowners (and a surprising number of contractors) get tripped up by the same handful of mistakes — almost always related to the difference between how big a window looks and how big its opening actually is. Let’s clear that up.

📋 When Is an Egress Window Required?

The OBC requires an emergency escape window (or door) in every bedroom located in a basement, and in every basement that doesn’t have direct access to an exterior exit at grade. The purpose is binary: if fire blocks the stairs, occupants must have another way out. No exceptions, no workarounds, no “but it’s just a guest room.”

This applies whether you’re building a brand-new home, finishing an unfinished basement with sleeping rooms, or creating a legal secondary suite under Ontario’s housing framework. If someone is going to sleep in a below-grade room, that room needs a compliant egress window. Period.

The one exception: if your basement has a walkout door that leads directly to grade, that door can serve as the emergency exit — provided the path from the bedroom to that door meets code requirements for travel distance and doesn’t pass through a furnace room or storage area that could be blocked. But for most Ontario basements — the kind where the windows are at or below grade and you access everything from interior stairs — you need egress windows.

Article 9.9.10 Part 9 – Housing and Small Buildings

📐 The Exact Size Requirements

This is where precision matters. The OBC doesn’t just say “install a big window.” It specifies a minimum clear opening — meaning the actual unobstructed space after you fully open the window. Not the glass area. Not the frame size. Not the rough opening in your foundation wall. The space a human being can physically fit through in a panic at 3 a.m.

Here’s the math that trips people up: 0.35 m² is about 540 square inches. If your clear opening is 15 inches wide (the minimum), then it needs to be about 36 inches tall to hit 540 square inches. But if both dimensions are at the minimum 15 inches, you only get 225 square inches — well under the 540 required. Both the area and the minimum dimension requirements must be met simultaneously. This is not an either/or situation.

🔍 Which Window Type Works Best?

Not all window styles deliver the same clear opening for their frame size. This is where your window choice can save you thousands of dollars in foundation work — or cost you a failed inspection and a reorder.

Awning windows (hinged at the top) are generally not suitable for egress. The opening geometry makes it extremely difficult for a person to climb through, and most building officials won’t accept them regardless of the clear opening area.

Hopper windows (hinged at the bottom, opens inward) — same problem. They might technically meet the area spec, but the opening direction makes escape impractical, and inspectors know it.

🕳️ Window Wells: The Part Everyone Forgets Until It’s Expensive

If your egress window is below grade (and in most Ontario basements, it will be), you need a window well — and the well has its own code requirements that are just as enforceable as the window specs.

The window well must be large enough for a person to stand in front of the open window and climb out. Think about that for a moment — this isn’t a decorative planter box. It’s an emergency escape route. If the well depth exceeds 600 mm (about 24 inches) from grade to the bottom, it must have a permanently attached ladder or steps. Not a loose piece of lumber propped against the wall. A permanent, fixed means of climbing out.

The well also needs proper drainage. In Ontario, that means a gravel base at minimum, and in many cases a drain tile connected to the weeping system or a sump. A window well that fills with water during spring thaw or a heavy rain is not just a code problem — it’s a flooded basement waiting to happen.

Here’s where timing matters: window well installation is a foundation and excavation decision, not a finishing detail. If you’re building new, the well location should be designed into the foundation plans from day one. If you’re building with ICF foundations, the window bucks (openings) are formed right into the wall during construction — far easier and cheaper than cutting concrete later. If you’re retrofitting an existing home, you’re looking at excavating along the foundation wall, cutting through concrete block or poured concrete, installing the window and frame, building the well with proper materials, and backfilling with drainage material. Budget $3,000–$8,000 per window well retrofit depending on access and depth.

🏠 Egress for Secondary Suites: Extra Rules Apply

If you’re building a legal basement apartment (secondary suite), egress requirements go beyond individual bedroom windows. The suite itself needs a safe exit path — typically a separate exterior door or a shared interior exit with proper fire separation. The exit route from the suite to the outdoors must not pass through the main dwelling’s living space. Your tenant can’t escape a fire by running through your kitchen.

Secondary suites also trigger additional requirements for fire separation, smoke and CO alarms, ceiling height, and independent heating — all of which interact with your egress plan. For the full picture, see our inspection sequence breakdown or check the Ontario government’s secondary suite requirements.

If you’re planning a new build with a suite included from day one, designing the egress and separate entrance into the original plans saves enormous cost compared to retrofitting later. The foundation cuts, window wells, drainage, and exterior grading are all dramatically simpler when they’re part of the initial design.

🔎 What Inspectors Actually Check (and How They Check It)

Understanding what happens during the inspection removes most of the anxiety. Here’s the process, based on watching hundreds of these inspections across Simcoe County, the GTA, and Georgian Bay:

Clear opening measurement: The inspector asks you to open the window fully. Then they measure the actual clear opening — height and width — with the window in its fully open position. If the window has a crank, they want it cranked all the way. They’re calculating whether the area meets 0.35 m² and whether both dimensions meet the 380 mm minimum. Some inspectors carry a test device; others use a tape measure and a calculator.

Sill height: Measured vertically from the finished floor to the bottom of the clear opening. Must be 1,500 mm or less. If you haven’t installed your finished floor yet, they may defer this measurement to final inspection — but you need to know the math works with your planned floor thickness.

Operability: The inspector will open and close the window themselves. It must operate without tools, without removing the sash, and without special knowledge. If your window requires a specific technique that isn’t obvious, it may be flagged. The window must also stay open on its own — if it slides shut under its own weight, that’s a fail.

Window well: If applicable, they measure the well dimensions, check for a ladder or steps if the depth exceeds 600 mm, and confirm drainage provisions. They may also check that the well cover (if present) is removable from inside without tools.

🎯 Are You Ready? Planning Checklist

Before you order a window or hire someone to cut your foundation, work through this self-qualification checklist. Getting these answers wrong costs real money.

💰 What Egress Windows Cost in Ontario

The window itself is rarely the expensive part. A quality casement egress window runs $400–$1,200 depending on size, material (vinyl, fibreglass, wood), and energy rating. The real cost is everything around it.

For new construction, egress windows are part of the foundation plan — the openings are formed during the pour (or built into the ICF wall assembly), and the wells are built during backfill. Incremental cost over a standard basement window: $500–$1,500 per window including the well. Minimal disruption because it’s planned from the start.

For retrofits (adding egress to an existing basement), the scope is bigger: excavation along the foundation, concrete cutting, structural lintels if needed, window installation, well construction, drainage, backfill, and grading. Budget $3,000–$8,000 per window in most Ontario markets, more if access is difficult or if the foundation is reinforced concrete.

If you’re building new and debating whether to include a bedroom in the basement, factor in the egress cost early. Use our ICF home cost calculator to get a broader picture of your foundation and below-grade costs — egress windows are a relatively small line item when they’re designed in from the start.

🔧 Ontario-Specific Considerations

A few details that apply specifically to building in Ontario:

Frost depth and footings: If your window well requires its own footing (common in deeper wells with masonry walls), that footing must extend below the frost line. In southern Ontario, that’s about 1.2 metres. In Simcoe County, Muskoka, and northern Ontario, it’s 1.5–1.8+ metres. This affects excavation depth and cost — don’t let a contractor estimate this without knowing your local frost depth.

Energy ratings: Ontario’s energy code (SB-12) requires windows to meet specific thermal performance values. Your egress window is no exception. In climate zones 1–3 (most of southern and central Ontario), you’ll need a window with an appropriate U-value and Energy Rating. This isn’t just a code box to check — a cheap, poorly insulated basement window in a Barrie or Orillia winter will condensate, frost, and eventually cause moisture problems in the wall below it.

Window well covers: Ontario winters dump snow. A window well without a cover will fill with snow and ice — blocking your emergency exit and potentially causing water intrusion during thaw. Clear polycarbonate covers are popular, but confirm with your building department that the cover can be opened from inside without tools. Some jurisdictions are stricter about this than others.

Permit requirements: Adding or enlarging a window opening in a foundation wall requires a building permit in virtually every Ontario municipality. The permit ensures the structural opening is properly supported (lintel/header) and the window meets code. Don’t skip this — cutting a foundation wall without engineering is how basements crack. For a summary of recent code updates that affect basement projects, see our 2024 OBC changes overview.

The harmonized 2024 OBC aligns closely with the National Building Code of Canada on egress requirements, so the fundamental specs are consistent — but Ontario’s energy and fire requirements add provincial layers you need to account for.