Every basement bedroom in Ontario needs an escape route, and for most homes that means an egress window: a 0.35 m² (3.8 sq ft) unobstructed opening with no dimension under 380 mm (15 inches), openable from inside without tools. Cutting one into a foundation costs $3,500–$6,000 in 2026. Here are the exact code numbers, the cost breakdown, and how the process works.
Ontario Egress Window Requirements at a Glance
The requirements come from the Ontario Building Code's bedroom-window provisions (OBC 9.9.10 and related sections). Here's what your window has to do:
| Requirement | Minimum | What It Means in Practice |
|---|---|---|
| Unobstructed open area | 0.35 m² (3.8 sq ft) | The clear opening when fully open — not the glass size |
| Minimum dimension | 380 mm (15 in) | No side of the opening may be narrower than 15 inches |
| Operation | No tools, keys, or special knowledge | Openable by a child in the dark; security bars must release from inside |
| Window well clearance | 760 mm (30 in) | If the window opens into a well, 30 inches clear in front of it |
| Casement into wells | Full-swing clearance | A crank casement must open fully within the well |
Common failure: a slider that meets the glass-area math but whose openable half falls under 0.35 m². Inspectors measure the actual clear opening with the window fully open — always run the math on the opening, not the unit size.
What an Egress Window Costs in 2026
A full egress installation — cutting the foundation, structural lintel, window, well, and finishing — runs $3,500–$6,000 in Waterloo Region. The breakdown:
- Concrete cutting and excavation: $1,500–$2,500 — sawing the foundation, digging the well area, disposal.
- Window unit: $650–$1,400 for a code-sized casement or slider, installed and flashed.
- Window well, drainage and gravel: $600–$1,200 including tying into weeping tile or a drainage pit.
- Structural lintel and engineering (where required): $400–$900.
- Permit: $200–$500 depending on municipality.
Already have a basement window that's just too small? Enlarging an existing opening runs $1,200–$2,500 — significantly cheaper than a fresh cut because the lintel zone and drainage path usually exist.
What Affects Your Quote
- Foundation type: poured concrete saws predictably; stone and block foundations need more careful structural work.
- Grade depth: the deeper the window sits below grade, the bigger the well and drainage requirement.
- Drainage situation: wells must drain — connecting to functioning weeping tile is cheap, but homes without it need a drainage pit or sump tie-in ($400–$1,000 extra).
- Interior finishing: jamb extensions, insulation, and drywall returns on the inside add $300–$700; plan it with the rest of your basement finish.
- Obstacles: gas meters, AC pads, decks, and property-line setbacks can force the window to a more expensive wall.
Window Wells, Drainage, and the Details That Fail Inspection
The well is where good installs go bad. Code requires 760 mm (30 inches) of clearance in front of the window, the well must sit below the window sill and drain freely, and any cover must be liftable from inside without tools. Corrugated steel wells are the budget standard; composite and stone-look wells add $200–$600 and look considerably better from inside the bedroom.
Drainage is non-negotiable: a well that holds rainwater becomes a window that leaks under hydrostatic pressure every spring. Gravel to the footing plus a tie-in to weeping tile is the standard detail — we deal with the fallout of skipped drainage constantly in our waterproofing-before-finishing work.
Permits and Process
Cutting a structural opening in your foundation requires a building permit everywhere in Ontario — this is not a grey area. The process in Kitchener, Waterloo, Cambridge, and Guelph: drawings showing the opening and lintel (your contractor or an engineer produces these), permit application ($200–$500), the cut and install, then inspection of the structural work before it's covered.
Door-to-door, a straightforward egress install is 2–4 days on site and 2–4 weeks including permit turnaround. If the window is part of a bedroom or second-suite project, bundle it into the main permit — see our basement permit guide and the full legal bedroom requirements checklist.
DIY vs Pro: Don't Cut Your Own Foundation
We're pro-DIY on plenty of basement scope, but this isn't the place. Foundation cutting involves structural loads (the wall above the opening needs a properly sized lintel), utility locates, shoring, and a saw that will hurt you. The failure modes — cracked foundations, sagging sills, chronic leaks — cost five figures to unwind.
Legitimate DIY adjacents: interior finishing around the new window, and prep like relocating storage and clearing exterior access, which can shave a few hundred dollars off the quote. For the cut itself, hire a crew that does egress windows weekly and pulls the permit as a matter of course. If you're planning the window as part of a bigger project, our basement egress planning guide covers sizing and placement strategy.
Frequently Asked Questions
What are the egress window requirements in Ontario?
A bedroom window must provide an unobstructed open area of at least 0.35 m² (3.8 sq ft) with no dimension less than 380 mm (15 inches), and must open from inside without tools, keys, or special knowledge. Windows opening into wells need 760 mm (30 inches) of clearance in front of the sash.
How much does an egress window cost in Ontario in 2026?
A complete new installation — concrete cutting, lintel, window, well, and drainage — runs $3,500–$6,000. Enlarging an existing undersized opening costs $1,200–$2,500. Permits add $200–$500 depending on the municipality.
Do I need a permit to install an egress window?
Yes. Cutting or enlarging a structural opening in a foundation requires a building permit in every Ontario municipality, with inspection of the lintel and structural work. If the window is part of a basement bedroom or second-suite project, it's bundled into that permit.
Does every basement bedroom in Ontario need an egress window?
Every basement bedroom needs a code-compliant escape opening. In practice that means an egress window unless the bedroom has a door directly to the exterior. A window elsewhere in the basement doesn't count — the opening must serve the bedroom itself.
How long does an egress window installation take?
2–4 days on site: day one for cutting and excavation, day two for lintel and window installation, then well, drainage, and finishing. Including permit turnaround, plan 2–4 weeks door-to-door. Spring and summer scheduling is tighter, so book ahead for fall projects.
Key Takeaways
- Ontario egress: 0.35 m² clear opening, no dimension under 380 mm, tool-free operation.
- New foundation-cut installs run $3,500–$6,000 in 2026; enlarging an existing opening $1,200–$2,500.
- Window wells need 760 mm clearance and real drainage — standing water means leaks.
- A building permit and structural inspection are mandatory everywhere in Ontario.
- Measure the actual clear opening, not the window size — sliders fail this constantly.
- Bundle the egress cut with your basement finish permit and project for the best pricing.
Devon has personally overseen 500+ interior renovations across Kitchener, Waterloo, Cambridge, and Guelph since 2018. Read full bio →
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