Basement finishing

Permitted basement finishing with proper moisture control, insulation, egress and alarms.

Finishing a basement in Ottawa needs a building permit. The City charges the permit on the finished floor area, and the plans show the walls, insulation, windows, any bathroom, and the smoke and CO alarms.

Moisture comes first. Leda clay holds water, and many Ottawa basements see some dampness in spring. Before framing, we check the grading and downspouts outside, look for cracks and efflorescence on the walls, and confirm the sump and backwater valve work. Wet walls get fixed before they get covered.

Walls are insulated to the Ontario Building Code with a moisture-tolerant layer against the concrete. The permit drawings list the insulation values the City expects to see at inspection.

A basement bedroom needs an egress window or door. The City of Ottawa's advisory sets the window opening at 0.35 m² or more, with no dimension under 380 mm, and 550 mm of clear space in front of it in the window well. Most older basement windows are too small, so the opening is cut larger and a new well is installed.

Since January 1, 2026, the Ontario Fire Code requires a CO alarm on every storey and next to each sleeping area in homes with a fuel-burning appliance, fireplace or attached garage. A new basement bedroom needs both smoke and CO alarms nearby.