Escape routes from basements that include a bedroom.

Often in the design of a basement, there is a need to include a bedroom in the design.  Basement bedroom create a for the occupant in the event of a fire blocking the exit stairs.  As a result, the Ontario Building Code requires a second means of exit, or egress, from the basement.  There are a few ways to accomplish this, but the most common method is an egress window.  The window is usually larger than most standard basement windows and therefore has minimum requirements for the opening design.

Clear opening in a window of the slider type.

The Ontario Building Code requires that the second exit have the following attributes:

1)  There must be no dimension smaller than 380mm (15″) and

2) the area of the opening must be no less than 0.35 sq. m.

For practical purposes, the window opening, clear of any obstruction, such as trim, stops or weather stripping must have a clear opening area of at least 0.35 sq. m. or 534 sq. in.

A simple formula for determining a compliant design is (window opening length) x (window opening height) must be equal to or greater than 0.35 sq. m.  and no opening dimension may be less than 380mm.

Once the window design is compliant, the space outside of the window must also be considered in the design of the exit path.  Included below is a clip from the appendix to the Ontario Building Code that illustrates acceptable exit spaces outside the egress window if the window looks out into a window well.

Egress window well minimum dimensions