What the 2024 Ontario Building Code requires for a basement bedroom window, why the window well is where most plans fail, and what an egress window costs on our quotes.
If your basement has a bedroom, the Ontario Building Code requires that floor to have at least one window you can climb out of, unless a door on the same level leads straight outside. The opening has to be at least 0.35 square metres, about 3.8 square feet, with no side narrower than 380 mm, or 15 inches. It has to open from the inside without tools and stay open on its own. If it opens into a window well, you need at least 550 mm of clear space in front of it. Plenty of original basement windows in GTA houses fail at least one of those tests, which is why the egress window is one of the most common lines we add to a basement quote that includes a bedroom.
The rule is Article 9.9.10.1 of the 2024 Ontario Building Code. It applies to every floor level that contains a bedroom, so one compliant window on the basement level satisfies it even if the basement has two bedrooms. The window needs an individual, unobstructed open portion of 0.35 square metres, measured with the window fully open, not the size of the glass or the frame. A sliding window is measured by its openable half only, which is why a wide slider that looks big enough often is not.
Upstairs, the window sill can be no higher than 1,000 mm above the floor. Basements are exempt from that sill limit, because most basement windows sit high in the foundation wall. The exemption does not mean a window at shoulder height is fine. Someone still has to reach it in the dark. The City of Ottawa's building code services, in its 2025 advisory on the 2024 code, says a high sill can be dealt with using stairs or built-in cabinets, and recommends no more than 1,000 mm from the top of that cabinet to the window. We can build that step into the millwork so it reads as a window seat rather than an afterthought.
A basement window that opens into a well needs 550 mm of clearance in front of it, about 21.7 inches. If the sash swings outward into the well, its swing cannot cut into that clearance in a way that blocks escape. If you cover the well with a grate or a bubble, the cover has to open from below without keys, tools or special knowledge. The Ottawa advisory adds a practical point: where the well is more than 1,000 mm deep, the occupant needs some way to climb out, which usually means steps or a ladder built into the well.
This is the part homeowners tend to skip. A new, larger window dropped into a shallow existing well can pass the window test and still fail the well test. When we enlarge a window, the well gets checked with it and often has to be replaced, and the grading and drainage around it get looked at too, because a deeper well that collects water is a leak waiting for the first big storm. Our waterproofing guide covers what has to happen at the foundation before any of that is finished inside.
You need an egress window when the basement contains a bedroom and there is no door on that level leading directly outside. A walkout or a separate side entrance with its own door can satisfy the requirement on its own, which is one reason homeowners planning a rental often build the separate entrance first.
You do not need one for a rec room, a gym, a theatre or an office, as long as nobody is sleeping there. Be honest with yourself about that word office. A room with a closet that a future buyer or tenant will call a bedroom gets judged as one by inspectors, appraisers and insurers. If there is any chance the room becomes a bedroom, size the window now, while the basement is unfinished and the work is cheapest. Rental suites carry their own requirements on top of this one, set out in our legal basement requirements checklist.
On Desire quotes, an egress window or window enlargement is priced as its own line. Across past projects in Mississauga, Brampton, Caledon and Scarborough, that line has run from about $1,500 to $2,800 per window, depending on the size of the opening and how much concrete has to be cut. Read what the line covers before you compare quotes. On one Scarborough job the window unit itself was priced separately from the enlargement, and the permit for the enlargement was its own item.
Cutting a larger opening in a foundation wall is structural work, so it needs a building permit, and the new opening needs a proper lintel above it. That is why a window enlargement should be drawn on the same permit set as the basement, not added as a favour from the framer halfway through the job. Our GTA permit guide lists what each municipality charges, and our building code guide covers the other 2024 code items that apply below grade.
At the consultation we measure the clear opening of the existing windows, not the frame, and look at the wells. If none of them passes, we pick the window that gives the best room layout, usually the one that lets the bedroom sit away from the furnace and the stairs, and enlarge that one. The 3D design shows the new window, the well and any built-in step before you commit, so you are not discovering a 4-foot sill after the drywall is up. The quote lists the egress window and the permit as their own lines, so you can see exactly what the bedroom is costing.
If you are planning a basement bedroom and are not sure your windows qualify, we will measure them at a free in-home consultation and show the fix in a free 3D design. If the plan is a rental unit, our legal basement apartment service covers egress, fire separation and the rest of the suite requirements in one permit.
Under Article 9.9.10.1 of the 2024 Ontario Building Code, the window must provide an unobstructed open area of at least 0.35 square metres, about 3.8 square feet, with no dimension less than 380 mm, or 15 inches. It must open from the inside without tools and stay open without additional support.
Where the egress window opens into a window well, the code requires at least 550 mm of clearance in front of the window. If a cover is installed over the well, it must open from the inside without keys, tools or special knowledge.
The Ontario rule applies per floor level, so at least one compliant window is required on any floor level containing a bedroom, unless a door on that level leads directly outside. Rental suites carry additional requirements, so confirm the layout with your designer before framing.
The 1,000 mm maximum sill height in the Ontario Building Code does not apply to basement areas. You still need to be able to reach and climb through the window, so a high sill is usually handled with built-in steps or cabinetry beneath it.
On Desire Basements quotes, an egress window or window enlargement has been priced at about $1,500 to $2,800 per window, depending on the opening size and the concrete cutting involved. Check whether the window unit, the well and the permit are included in that line or listed separately.
Kam walks the space, draws it in 3D and sends an itemized estimate within 24 to 48 hours. No allowance lines, no surprises.
Get a Free Estimate
