Yes, a casement window can be an egress window — and in many cases it is the easiest window type to make code-compliant. Because the entire sash swings outward on a side hinge, a casement provides a wide, unobstructed clear opening. As long as the window meets the Ontario Building Code (OBC) minimums for opening area, height, width, and sill height, it qualifies as an egress window.
This matters most in finished basements and sleeping rooms where at least one window must allow occupants to escape in a fire and give firefighters a way in.
What Is an Egress Window, Exactly?
An egress window is any window that can be used as an emergency exit. Ontario’s Building Code (Part 9, Section 9.7.2) sets out specific requirements for windows in rooms used for sleeping, and in basement spaces that are finished as living areas.
The window does not need a special label or product designation — it simply has to meet the dimensional minimums when fully open. That is why the style of the window matters: a fixed pane or a window that only opens partway will not qualify, no matter how large the glass area looks from inside.
Ontario Building Code Egress Requirements
The OBC sets out four measurements you must satisfy. All four must be met at the same time — there is no picking and choosing.
| Requirement | Minimum |
| Clear opening area | 0.35 m² (3.77 sq ft) |
| Clear opening height | 380 mm (15 in) |
| Clear opening width | 450 mm (17.7 in) |
| Sill height above finished floor | No more than 1,000 mm (39.4 in) |
“Clear opening” means the usable space after the frame, screens, hardware, and any fixed mullions are subtracted. The sill height rule exists so that an adult can actually reach and climb through the window without a step or ladder.
Note: Some municipalities in the GTA may interpret or enforce additional local requirements. Always confirm with your local building department before ordering.
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Why Casement Windows Work Well for Egress
A casement sash rotates on a vertical hinge and opens fully to one side. This means nearly the entire rough opening becomes clear opening space. Compare that to a double-hung window, where you can only open the lower half, or a sliding window, where roughly half the frame is always fixed.
For this reason, casement window replacement is a popular choice when homeowners are converting a basement bedroom or updating an older sleeping room to meet current code.
Other reasons casement windows suit egress applications:
- No raised sash to climb over — the opening is flush with the frame
- Side-hinged operation is easy to push open from inside, even under stress
- Mechanical crank hardware opens the window quickly with one hand
- Multipoint locking seals tightly when closed, limiting air and water infiltration
- Available in a wide range of sizes to hit the 0.35 m² minimum with room to spare
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Comparing Window Types for Egress Suitability
Not every window style can reach the 0.35 m² clear opening threshold, even at a standard residential rough opening size. Here is a quick comparison:
| Window Style | Can It Be Egress? | Notes |
| Casement | Yes — easily | Full sash opens; high clear-opening ratio |
| Awning | Sometimes | Opens outward at the top; width limits can be an issue in narrow openings |
| Double-hung | Sometimes | Only half the sash opens; larger rough opening needed |
| Slider (horizontal) | Sometimes | Half the frame is fixed; requires a wide rough opening |
| Fixed / picture | No | Does not open; never qualifies as egress |
| Hopper (inward swing) | Rarely | Low clear height; depth of swing can obstruct the opening |
If you are replacing fixed replacement windows in a basement bedroom, you will need to switch to an operable style — a casement is the most straightforward swap in a standard-width opening.
Basement Egress: A Special Case
Basement sleeping rooms are where most egress questions come up. The OBC requires at least one egress window in any basement room intended for sleeping. The 1,000 mm sill-height rule is harder to satisfy in basements because the floor sits lower than grade — a standard basement window well may not be deep enough, and the window itself may sit near the top of the wall.
In practice, this often means:
- Cutting a larger rough opening to fit a taller sash
- Installing or enlarging a window well to allow climbing clearance at grade
- Choosing a casement or awning style to maximise clear opening area in the available rough opening
If you are finishing a basement, an egress window replacement is typically required before the permit can close.
Size Chart: Common Casement Sizes vs. Egress Threshold
| Casement Sash Size (W × H) | Approximate Clear Opening | Meets 0.35 m²? |
| 400 mm × 800 mm | ~0.28 m² | No |
| 500 mm × 800 mm | ~0.36 m² | Yes |
| 600 mm × 700 mm | ~0.38 m² | Yes |
| 700 mm × 600 mm | ~0.38 m² | Yes |
| 600 mm × 900 mm | ~0.49 m² | Yes |
Clear opening dimensions deduct frame width and hardware overlap. Actual figures vary by manufacturer — always confirm with the window supplier before ordering.
What Professionals Say
“Casement windows are genuinely the easiest route to egress compliance in a tight rough opening. The full-sash swing means you get almost all of your frame area as usable exit space, which is something you simply cannot get from a half-sliding or half-open double-hung. When I’m inspecting a basement bedroom permit, casements almost never fail the opening area test — it’s the sill height that catches people off guard.”
— David Kowalczyk, Certified Building Inspector, Peel Region, Ontario (20+ years of residential inspections)
“What homeowners miss is that egress is a minimum — not a target. I always recommend going at least 15–20% above the 0.35 m² threshold so that there is tolerance for hardware overlap and frame variation between manufacturers. A 600 × 900 mm casement gives you a comfortable buffer and still looks proportional in a basement wall. Ordering right at the legal minimum is a gamble I would not take with a permit on the line.”
— Sandra Pieterse, Registered Building Designer (AIBC), Burlington, Ontario
ENERGY STAR™ and Egress Windows
Choosing an egress window is also a chance to improve the thermal performance of a basement or sleeping room. ENERGY STAR™ certified windows are rated for specific Canadian climate zones, and many high-performance casements qualify. TotalSeal manufactures ENERGY STAR™ certified vinyl casements with Low-E coatings, argon gas fills, and warm-edge spacers — meaning the window that meets your safety code can also cut heating costs in a GTA winter.
If you are shopping for casement window types and comparing performance specs, check the U-factor and ER (Energy Rating) values against the ENERGY STAR™ zone requirements for Ontario (Zone 2).
Tips Before You Order
- Measure the rough opening, not the existing window frame — old frames can be smaller than the rough opening behind them.
- Confirm the sill height with a tape measure from the finished floor, not the subfloor.
- Ask your window supplier for the certified clear opening dimensions, not the nominal sash size.
- If you are adding an awning window replacement to a narrow opening, double-check the 450 mm minimum width — awning styles can be tight on width.
- A building permit is required for most egress window installations that involve changing the rough opening size.
If you are unsure whether your planned window qualifies, the team at TotalSeal can review your rough opening measurements and confirm which sizes will pass inspection. Contact us for a free consultation.
FAQ
Does a casement window automatically qualify as an egress window?
No. A casement style opens in a way that is well-suited to egress, but it must still meet the OBC minimums: 0.35 m² clear area, 380 mm clear height, 450 mm clear width, and a sill no higher than 1,000 mm above the finished floor.
Can a casement window with a screen count toward the egress area?
No. Screens are counted as obstructions. The clear opening is measured with the screen removed or opened. A removable insect screen is acceptable as long as it can be taken out quickly from inside.
Do I need a permit to install an egress window in Ontario?
Yes, in most cases. Any work that changes the size of a rough opening or adds a new window opening requires a building permit. Replacing an existing window with the same rough opening size is generally exempt, but always check with your local municipality.
What is the maximum sill height for an egress window in a basement bedroom?
The Ontario Building Code requires the sill to be no more than 1,000 mm (about 39 inches) above the finished floor. If the existing window sits higher than this, the rough opening may need to be lowered.
Can a double casement (two sashes side by side) count as one egress window?
Only if the operable sash alone meets the minimum clear opening requirements. If each individual sash is too small on its own, having two of them side by side does not combine their areas for egress purposes.
