Short answer: every bedroom in a basement suite needs a way out that does not depend on the stairs — either a door to the outside or a basement egress window. The Building Code requires the window to open from inside without keys or tools, to stay open on its own, and to give an unobstructed opening of at least 0.35 m² (about 3.8 sq ft) with no dimension under 380 mm (15 in). If the window sits in a well, the well needs about 550 mm (22 in) of clear space in front of the glass. Most original basement windows in GTA houses do not meet that, so the job is usually cutting the foundation to enlarge the opening, setting a steel lintel, installing a full-opening window and building a drained well. There is no flat price for it — it is quoted on site — and in a legal suite it is bundled into the Suite + Entrance package. Below: the numbers, how to check your own window, the options, the process and what drives the cost.
Egress window requirements at a glance
| Requirement | Metric | Imperial | Notes |
|---|---|---|---|
| Unobstructed opening area | ≥ 0.35 m² | ≈ 3.8 sq ft | Measured on the clear opening with the sash open, not the frame size |
| Minimum dimension | ≥ 380 mm | ≥ 15 in | Applies to both height and width of the clear opening |
| Operation | Opens from inside without keys, tools or special knowledge; stays open without being held | Rules out most sliders with screens that fall out and any window with a lock-only latch | |
| Window well clearance | ≈ 550 mm | ≈ 22 in | Clear space between the glass and the well wall so a person can climb out |
| Where required | Every bedroom without a door directly to the outside; the suite as a whole also needs its exit path | ||
These figures come from the Building Code’s second-unit provisions for existing houses; your designer confirms the exact sill height, well dimensions and any bars-or-grilles rules for your house as part of the permit drawings. The complete set of second-unit rules — fire separation, alarms, ceiling heights — is in our guide to legal basement apartment requirements in Ontario.
Does your current window pass?
Open the window as far as it goes and measure the hole a person would climb through — the clear opening — not the frame or the glass. A window with a 24 in × 24 in frame can have a clear opening well under half that once the sash, track and screen are counted. Then check the two numbers: is the smaller dimension at least 15 in, and does width × height come to at least 3.8 sq ft? Both have to pass. Finally, check that it opens without a key, that a screen does not have to be removed with tools, and that it stays open by itself.
The typical basement window in a 1960s–1990s GTA house is a short hopper or slider set high on the wall, and it fails on the height dimension, on the clear area, or on both. That is not a defect — it was never meant to be an exit — but it means a bedroom cannot go behind it until the opening is changed.
Four ways to get a compliant exit
- Enlarge the existing opening downward. The most common route. The foundation below the current window is cut to make the opening taller, a lintel is set if the width changes, and a larger window goes in. It keeps the window where the framing and the exterior already expect it.
- Cut a new opening. When the bedroom is in a part of the basement with no window, or the existing one is under a deck or porch where a well cannot go. Location is chosen around the joists, services and what is outside.
- Replace the window unit only. If the opening is already large enough but the window is a slider that gives up half its area to the fixed pane, a casement that swings fully open can pass in the same hole. This is the cheapest fix and it is worth checking before anyone cuts concrete.
- A walkout or egress door. An exterior door to grade, or a walkout stair, satisfies the requirement for the bedroom it serves and gives the suite its own entrance in the same stroke. It is the largest scope of the four and is the basis of the legal basement apartment Suite + Entrance package.
How an egress window is installed
- Layout. The opening is marked inside and out from the permit drawings, and utilities behind the wall are located.
- Excavation. The soil outside is dug to below the new sill, deep enough for the well and its drainage.
- Cutting. The foundation — poured concrete or block — is saw-cut with water suppression and the section removed. This is loud, wet work for a few hours.
- Lintel. A steel lintel is set above the opening where the width has grown, so the wall above carries its load properly.
- Window. A buck frame is anchored into the opening, the window unit set level, sealed and insulated.
- Well. A galvanized or composite well is fastened to the foundation and backfilled with gravel to a drain; a cover goes on top.
- Inside finish. The jamb is framed, insulated and drywalled, then trimmed like any window.
- Inspection. The municipality inspects the opening and the well as part of the second-unit permit, along with the rest of the suite.
What drives the cost
There is no per-window price on our site because the same window can be a modest job or a major one depending on the house. What sets the number:
- Foundation type. Block is faster to cut than poured concrete; poured concrete with reinforcing is the slowest.
- Depth. How far below grade the sill ends up decides the excavation, the well height and whether the well needs a ladder.
- Access. A window on the driveway side is a different job from one in a narrow side yard behind a fence with an air-conditioner in the way.
- Drainage. Whether the well can drain to a weeping tile or needs its own dry well.
- Interior finish. Framing and drywall around the new jamb, and any patching where the old window was.
Cutting the foundation, the steel lintel, the window unit, the well and the drainage are the cost drivers, and they are quoted on site after we see the wall and the yard. In a legal suite, enlarged windows and window wells are part of the Suite + Entrance package at $150–190 per square foot — the price and the other two packages are broken down in our guide to legal basement apartment cost in the GTA. A single egress window for a bedroom in a regular basement renovation is quoted as its own line on that project. One honest limit: if the wall around the window is cracked, leaking or bowed, that is foundation repair or waterproofing, and it goes to a foundation contractor before we cut anything.
Window wells: size, drainage and covers
A well is not just a hole to let light in; it is the space a person stands in while climbing out, which is where the 550 mm clearance comes from. Practical details that make a well work year after year: a bed of gravel at the bottom connected to a drain so rain and snowmelt do not sit against the window, a well that sits a little above finished grade so surface water runs away from it, and a clear cover that keeps out leaves, snow and small children while still opening from inside without tools. A cover that has to be unbolted defeats the purpose of the window.
Mississauga, Brampton and Toronto
Egress is checked as part of the second-unit permit in every GTA municipality, and the inspector looks at the clear opening and the well with a tape measure. What differs is the house. Mississauga and Brampton lots usually have the side-yard room for a well and a driveway to work from — see legal basement apartments in Mississauga and legal basement apartments in Brampton. Toronto semis and narrow detached lots often have no side yard to speak of, so the window goes to the rear, or the exit becomes a walkout; details on legal basement apartments in Toronto.
IntraBuild designs, permits and builds second units across the GTA, egress windows included: one insured crew, drawings and inspections handled, a written price, no travel fee. Get a legal basement apartment quote or call (647) 558-8723.
Frequently asked questions
What size does a basement egress window have to be in Ontario?
An unobstructed opening of at least 0.35 m² (about 3.8 sq ft) with no dimension under 380 mm (15 in), measured on the clear opening with the window open. It must open from inside without keys or tools and stay open on its own. Your designer confirms sill height and well details for your house.
Does every basement bedroom need one?
Every bedroom needs either an egress window or a door directly to the outside. A bedroom with neither cannot be counted as a bedroom on the permit, no matter how it is finished.
Can I use a walkout door instead?
Yes. An exterior door from the bedroom, or a walkout that serves the suite, satisfies the exit requirement and doubles as the suite’s separate entrance. It is more work than a window but solves two problems at once.
How much does an egress window cost?
It is quoted on site. Cutting the foundation, the steel lintel, the window unit, the well and the drainage set the price, and they vary a lot house to house. In a legal suite, enlarged windows and wells are included in the Suite + Entrance package at $150–190 per square foot, before HST.
Do window wells need drains?
In practice, yes. A well without a drain fills with rain and snowmelt and the water ends up against the window and the foundation. A gravel base tied to the weeping tile or a dry well, plus a cover, is what keeps the window dry and the basement with it.
