How do I cut a window well into an Ottawa concrete foundation?

Cutting an egress window well into a concrete foundation is a complex, high-stakes project that requires careful planning, the right equipment, and in most cases, a building permit from the City of Ottawa.

Cutting through a poured concrete or concrete block foundation isn't a typical DIY job — it involves diamond-blade core saws or wall saws, structural considerations, and proper lintel installation to redistribute the load above the opening. That said, understanding the full process helps you ask the right questions and make informed decisions.

The basic process starts well before the saw touches concrete. You'll need to identify exactly where your utilities run (hydro, gas, water, drainage) both inside and outside the foundation wall. Call Ontario One Call (1-800-400-2255) to have underground utilities located — this is free and legally required before any digging in Ontario. Once you've confirmed the location is clear, you'll mark your opening, typically a minimum of 900mm wide × 1000mm tall for a proper egress window in Ontario.

The cutting itself requires professional-grade equipment. Most contractors use a hydraulic wall saw or a track-mounted diamond saw to make precise cuts. After the opening is cut, a steel or precast concrete lintel must be installed immediately above the opening to carry the load of the foundation wall and structure above. Skipping or undersizing the lintel is one of the most dangerous mistakes in this type of work — it can lead to wall cracking or, in worst cases, structural failure.

Ottawa-Specific Permit Requirements

The City of Ottawa requires a building permit for any new window opening cut into a foundation wall. This applies even if you're simply enlarging an existing window. Permits are processed through ottawa.ca/building or by calling 613-580-2424, and typically take 10–20 business days for straightforward residential applications. The permit process ensures your lintel sizing and window installation meet the Ontario Building Code (OBC), which specifies minimum egress dimensions, well depth, and drainage requirements.

For egress windows specifically, the OBC requires the window well to be at least 550mm deep from the exterior grade, with a gravel drainage bed at the bottom to prevent water pooling. Ottawa's frost line sits at 4 feet deep, so proper drainage is critical to avoid freeze-thaw damage to the well and surrounding foundation.

Should You DIY This?

Honestly, this is one of the more challenging basement projects to DIY. The cutting itself can be rented out (diamond wall saws are available at Ottawa equipment rental shops), but lintel installation and structural assessment really should involve a professional. If your home is older (pre-1980s), your foundation may be rubble stone or older block construction, which changes the structural approach significantly.

Typical costs in the Ottawa market for a professionally installed egress window including the cut, lintel, window well, and window unit run roughly $3,500–$5,500 depending on foundation type, depth, and accessibility. DIY savings on the labour are real, but the permit, lintel, and window materials alone will still run $1,200–$2,000.

If you're adding an egress window as part of a basement finishing project or secondary suite conversion, Ottawa Basements handles the full scope — permits, cutting, structural work, and installation. Reach out for a free estimate and we can assess your specific foundation type and location before any work begins.