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 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 below grade 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 rules are straightforward once you know them. But most homeowners – and a surprising number of contractors – trip on the same handful of mistakes, almost always about 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 that every floor level containing a bedroom have at least one outside egress window – unless a door on that same level provides direct access to the exterior. It is written per floor level, not strictly per bedroom, but in practice each below-grade sleeping room needs a compliant escape route. The purpose is binary: if fire blocks the stairs, occupants must have another way out. 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 level needs a compliant egress window.

The exception the code actually gives: if a door on the same floor level provides direct access to the exterior (a walkout, for example), that door can serve as the escape – provided the path to it meets code and doesn’t rely on passing through a room that could be blocked. But for most Ontario basements – windows at or below grade, everything reached from interior stairs – you need egress windows.

OBC 9.9.10.1 Part 9 – Housing & Small Buildings

The exact size requirements

This is where precision matters. The OBC specifies a minimum clear opening – the actual unobstructed space with the window fully open. 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 545 square inches. If your clear opening is 15 inches wide (the minimum), it needs to be about 36 inches tall to hit 545 square inches. But 15 inches by 15 inches is only 225 square inches – well under what’s required. Both the area and the 380 mm minimum-dimension rule must be met at the same time. It is not either/or.

Which window type works best?

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

Awning windows (hinged at the top) are generally not suitable – the opening geometry makes it very hard to climb through, and most officials won’t accept them regardless of area. Hopper windows (hinged at the bottom, opening inward) have the same problem: they may meet the area on paper, but the 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 enforceable code rules. The OBC requires at least 550 mm of clearance in front of the window, so a person can stand in front of the fully open window and climb out. This isn’t a decorative planter box – it’s an emergency exit.

If the sash swings into the well, its operation must not reduce that clearance in a way that would restrict escape. And where the window well is more than 1,000 mm deep, you must provide a means to assist the occupant out – permanent steps or a fixed ladder, not a loose board propped against the wall. If a protective cover is fitted over the well, it must open from the inside without keys, tools, or special knowledge.

The well also needs proper drainage – a gravel base at minimum, and in many cases a drain connected to the weeping system or a sump. A well that fills during spring thaw isn’t just a code problem; it’s a flooded basement waiting to happen.

Timing matters: a window well is a foundation and excavation decision, not a finishing detail. On a new build, the well location belongs in the foundation plans from day one. With ICF foundations, the window bucks are formed right into the wall during construction – far cheaper than cutting concrete later. On a retrofit you’re excavating along the wall, cutting through block or poured concrete, setting the window and header, building the well, and backfilling with drainage material. Budget roughly $3,000 to $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, egress goes 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 – and the 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 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 the Ontario government’s secondary-suite requirements. If you’re planning a new build with a suite from day one, designing the egress and separate entrance into the original plans saves enormous cost versus retrofitting later.

What inspectors actually check (and how)

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

Clear opening: the inspector asks you to open the window fully – crank all the way if it’s a casement – then measures the actual clear opening, height and width, in that fully open position. They’re checking the area meets 0.35 m2 and both dimensions meet 380 mm.

Sill height: measured from the finished floor to the bottom of the clear opening. Above-grade bedrooms have a 1,000 mm max; basements are exempt from that max, but the opening still has to be reachable, and where the sill is high, steps, a built-in cabinet, or a counter can be used to reach it. If your finished floor isn’t installed yet, they may defer this to final – but the math has to work with your planned floor thickness.

Operability: the inspector opens and closes the window themselves. It must work without tools, without removing the sash, and without special knowledge, and it must stay open on its own – if it slides shut under its own weight, that’s a fail.

Window well: if applicable, they measure the clearance (at least 550 mm), check for steps or a ladder where the well is deeper than 1,000 mm, confirm drainage, and check that any cover opens from inside without tools.

Are you ready? Planning checklist

Before you order a window or hire someone to cut your foundation, work through this. Getting these 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 to $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: roughly $500 to $1,500 per window including the well, with minimal disruption because it’s planned from the start.

For retrofits, the scope is bigger: excavation along the foundation, concrete cutting, a structural lintel if needed, window install, well construction, drainage, backfill, and grading. Budget $3,000 to $8,000 per window in most Ontario markets, more if access is difficult or the foundation is reinforced concrete.

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

Ontario-specific considerations

Frost depth and footings: if a window well needs its own footing (common in deeper wells with masonry walls), that footing must extend below the frost line – roughly 1.2 m in southern Ontario, and 1.5 to 1.8 m or more in Simcoe County, Muskoka, and the north. That affects excavation depth and cost, so don’t let a contractor estimate it without knowing your local frost depth.

Energy ratings: Ontario’s energy provisions (SB-12) require windows to meet thermal-performance values, and your egress window is no exception. 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 well without a cover fills with snow and ice, blocking the exit and inviting water at thaw. Clear polycarbonate covers are popular, but confirm the cover opens from inside without tools – the OBC requires exactly that where a protective enclosure is fitted.

Permit requirements: adding or enlarging a window opening in a foundation wall requires a building permit in virtually every Ontario municipality – it ensures the opening is properly supported (lintel/header) and the window meets code. Cutting a foundation without engineering is how basements crack. For recent code updates that affect basement projects, see our OBC changes overview. The current 2024 OBC harmonizes closely with the National Building Code of Canada on egress, so the core specs are consistent, though Ontario’s energy and fire layers add provincial requirements.

A story from the field

A homeowner in Innisfil called me last spring – she’d already bought four sliding windows for her basement bedrooms on a contractor’s recommendation. Nice windows, good brand. But when we checked the clear opening on the spec sheet, each one fell about 40 square inches short of the 0.35 m2 requirement: the sliders only opened halfway, and half of a 24 in by 30 in slider doesn’t get you there. She returned all four and replaced them with casements that were actually smaller in frame size but delivered a larger clear opening. It cost her a restocking fee and two weeks – but saved four failed inspections. The lesson: the spec sheet is your friend; the catalogue photo is not.

Related guides

Egress windows in Ontario: frequently asked questions

Disclaimer: general information only. Building code requirements can vary by municipality and are subject to local amendments. Always confirm requirements with your local building department, the Authority Having Jurisdiction, or a qualified professional before starting construction. This is not legal advice.