Bedroom egress is governed by Section 9.9.10 of the Ontario Building Code. Article 9.9.10.1 is worth reading closely, because several details are commonly misquoted online. A compliant egress window must:
The Code sets a maximum sill height of 1,000 mm above the floor but exempts basement areas from that limit, so a basement bedroom sill can sit higher. However, the opening still has to be genuinely usable in an emergency, and plans examiners will look at how an occupant reaches it. Where a sill is high, permanent steps, a built-in cabinet or a counter below the window are common solutions. Many designers keep basement sills at or below 1,000 mm anyway, because it is the easiest position to defend at inspection.
The OBC requires every floor level containing a bedroom in a suite to have at least one compliant outside window. This differs from the National Building Code, which requires egress for each bedroom. There is also an important exemption: where a door on the same floor level provides direct access to the exterior, the egress window is not required. A basement suite with its own side entrance or walkout may already meet the requirement through that door.
| Confirm before you cut: Municipal interpretation varies across the GTA, and the Ontario Fire Code sets separate requirements for rental units. Confirm the number and location of required egress openings with your designer and local building department before drawings are finalized. That confirmation is free. Cutting a second opening you did not need is not. |
Pre-1960 homes. Original basement windows are typically narrow hopper or casement units set at or just below grade, sized for ventilation rather than escape. Clear openings of 0.1 to 0.2 m² are common, with widths of 300 to 400 mm and heights of 200 to 300 mm. These fall well short of the 0.35 m² minimum and usually the 380 mm minimum dimension too.
Post-war and 1970s homes. Frames are often larger, but they fail on a different point: only the openable portion counts. A horizontal slider opens roughly half its width, so a 1,200 x 600 mm slider may deliver barely half the clear opening a homeowner assumes. The 380 mm minimum applies to the openable portion, not the frame.
Before assuming a cut-out is needed, have the existing windows measured properly. What matters is the clear opening with the window fully open, measured between sashes, jambs, sill and hardware. Manufacturer spec sheets list clear opening dimensions, and those figures, not frame sizes, are what an inspector checks.
A masonry cut-out modifies the foundation wall of the house, so it requires a building permit and, in most cases, engineering input.
Virtually every residential foundation wall in the GTA is load-bearing, so a lintel must be installed above the enlarged opening. Lintel size, bearing length and installation sequence are confirmed by a structural engineer or the OBC prescriptive lintel tables before any cutting begins, along with temporary shoring requirements.
Drywall, insulation and framing next to the opening are removed to expose the foundation wall and give access for interior trim once the window is in.
The exterior grade is prepared, including removing or protecting any existing window well, landscaping or hardscaping. Utility locates are essential, since gas lines, water services and buried electrical often run close to foundation walls on older GTA lots.
The wall is cut with a diamond saw or core drill to the size of the new opening plus clearance for the frame. Precision matters both ways: an oversized cut creates structural and waterproofing problems, and an undersized cut has to be redone. Poured concrete walls are saw cut. Concrete block walls sometimes allow individual blocks to be removed, though irregular courses often still need saw cutting for a clean opening.
The lintel is set above the opening and bears on intact masonry at both sides before it takes load. Temporary shoring stays in place until the lintel is fully installed as specified.
The new window is installed, flashed, insulated and sealed. Waterproofing at the head and jambs is critical below grade, because the new opening interrupts the existing foundation damp-proofing.
Where the window sits below grade, a window well holds back soil and admits light. For egress, it must provide at least 550 mm of clearance in front of the window so an occupant can get out and stand up, and any sash swinging into the well must not block escape.
Inside, the opening is framed, insulated, drywalled and trimmed. Outside, the grade is repaired, the well backfilled and the exterior trimmed or caulked, with final grading sloped away from the well.
Typical GTA pricing for an egress window cut-out, including cutting, lintel, window supply and installation, window well, and interior and exterior finishing:
| Scope | Typical Range |
| Single cut-out, poured concrete foundation | $1,800 to $3,500 |
| Single cut-out, concrete block foundation | $1,500 to $2,800 |
| Each additional cut-out, same project | $1,200 to $2,500 |
Additional openings cost less because mobilization, shoring equipment and disposal are already on site. These ranges assume a straightforward cut in an accessible section of wall. Costs rise with:
Not included: structural engineering fees, the building permit, and any interior layout changes triggered by moving a bedroom to a wall that can accept a cut-out.
The most expensive version of this job is the one discovered after framing has started. When a basement layout places bedrooms against the wall with the most workable window position, the number of cut-outs can drop from two to one, or to none where a direct exterior door already serves the level. At Maple Leaf Quality Renos, we measure every existing basement window during the initial site assessment, confirm which ones meet the clear opening requirements, and set the cut-out scope before layout drawings are finalized. You know the full project cost before construction begins, and the permit closes without a late structural surprise.
Contact us for a free site assessment.
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