Legal Basement Bedroom Windows
If someone sleeps in the basement, the window is not a detail. It is the way out. Ontario code puts numbers on that: an opening big enough to climb through, with room outside to escape. Send us photos of the window and we will tell you what it takes: written, itemized, and guaranteed to pass inspection.
What Ontario Code Requires
The Ontario Building Code sets four conditions for an egress window in a basement bedroom, the window meant as your way out in an emergency. The size is measured on the clear opening, the space you can climb through with the window fully open, not on the glass.
- An opening of at least 0.35 square metresAbout 3.8 square feet of clear, unobstructed opening, with no dimension smaller than 380 mm.
- Openable from inside without toolsNo keys, tools, or special knowledge. If it is painted shut or a bar has to come off first, it fails.
- Stays open on its ownOnce it is open, it has to hold itself open with nothing propping it, so the way out stays clear.
- 550 mm of clearance in the window wellAbout 22 inches of room outside the window to escape. A cover has to open from inside without tools, and a sash that swings into the well cannot cut into the clearance.
The Ontario Building Code requires at least one egress window on each floor level that contains a bedroom, unless a door on that same level leads straight outside. A basement apartment counts on its own. We size to the strictest reading, which is why our installs are guaranteed to pass inspection.
What Is the Legal Window Size for a Basement Bedroom in Ontario?
Big enough for an adult to climb out of with the window fully open. It is measured on the space that opens, not the glass. In a basement there is no limit on how high the sill, the bottom edge of the window opening, can sit, but the well outside needs room to crawl out too.
The minimum egress window size in Ontario is 0.35 square metres of clear opening, about 3.8 square feet, with no dimension smaller than 380 mm, about 15 inches. Both rules apply at once: a long, thin opening fails on the short side even when the area passes. Those numbers, plus the well clearance below, are the basement bedroom window requirements in Ontario that an inspector actually measures.
- 0.35 m² minimum clear openingAbout 3.8 square feet, measured with the window fully open. The glass size on the sticker is not the number that counts.
- No dimension under 380 mmAbout 15 inches. At the 380 mm minimum on one side, the other side must run at least 921 mm, about 36 inches, to reach 0.35 m².
- No maximum sill height in a basementAbove grade, the sill can be no higher than 1,000 mm, about 39 inches, off the floor. Basement bedrooms are exempt, so a high sill alone does not fail a basement window.
- 550 mm of clearance in the wellAbout 22 inches, measured out from the window face. A sash that swings outward eats into this dimension, which is why we install tilt and turn windows that open inward.
This is where most oversized quotes come from. A window company that only carries double sliders will often tell you the opening has to grow to 48 by 36 inches. That is what their window needs, not what the code asks for. A slider only opens on one side, so a 48 inch frame can never give more than 24 inches of clear width.
The tilt and turn windows we install open inward like a fridge door, and nearly the whole frame counts. Frame for frame, that is about twice the clear opening of a slider, which is how a window a full foot narrower passes the same code. We size from the clear opening, not the glass. If your window falls short, the fix is a bigger opening in the foundation, and usually a smaller one than a slider would need. That job is covered on replacing a basement window with an egress.
Why Most Basement Windows Fail
Most basements were not built for sleeping. The windows are the proof.
- The glass is bigger than the openingA slider or hopper only opens half its frame. Measured on the clear opening, most fall short of 0.35 square metres.
- The well is too tightMany older steel wells sit closer than 550 mm, about 22 inches, to the window. The window can pass while the well fails.
- Bars and covers that do not releaseFixed security bars and screwed-down covers fail the no-tools rule. A quick release from inside keeps them legal.
- Painted shut, swollen shut, storm windowsIf it does not open without a fight, it does not count as a way out.
What It Takes to Fix
Making a window legal usually means making the opening bigger, and that is concrete work, not window work. We cut the foundation, dig by hand beside gas lines, patios and gardens, set the window, build the well with the full clearance Ontario code asks for, and run drainage down to the weeping tile, tested with a running hose before we backfill.
One detail that matters in a well: a sash that swings outward can eat the clearance the code requires. The European tilt and turn we install opens inward, so the well stays clear.
Complete installation starts at $3,999.99, one team, no subcontractors. The cost page shows exactly what that covers, including the well and the drainage.
Guaranteed to Pass Inspection
1000+ egress installs across Southern Ontario since 2021. Three year water free warranty, five years on parts and the window. The same crew cuts, digs, builds and cleans up.
“Steve and crew did a great job installing two large egress windows on a older home in St Catharines. Due to the size, one window required a custom concrete wall well with stone capping that looked awesome and is highly recommended.”
Asked on Almost Every Job
- Does every bedroom need its own egress window?Not under Ontario code. The Ontario Building Code asks for at least one egress window on each floor level that has a bedroom, unless a door on that same level leads straight outside. A basement apartment counts on its own. If bedrooms will be locked, as in shared living, we recommend one in each. Send photos of your layout and we will tell you what it needs.
- Can my existing window count?Sometimes. Open it fully and measure the clear opening. Under 0.35 square metres, a side under 380 mm, or a well tighter than 550 mm means it does not count.
- Do security bars fail inspection?Fixed bars fail. Bars with a quick release that opens from inside without tools can pass.
- Is the window enough to make the bedroom legal?It is the biggest piece, but ceiling height, smoke alarms and ventilation matter too, and basement apartments carry more. The window and everything outside it is the part we do.
Get a Free Estimate From Photos
Send photos of your basement wall, inside and out. You get a written estimate without booking a site visit. If the bedroom you are planning needs a bigger opening, you will know the number before anyone digs.