What is the minimum unobstructed opening area required for a basement bedroom window?

• A. 0.25 square metres (2.69 square feet)
• B. 0.35 square metres (3.77 square feet)
• C. 0.50 square metres (5.38 square feet)
• D. 0.75 square metres (8.07 square feet)

Answer: (B)

The key idea is life-safety egress from a basement bedroom. When a bedroom is in a basement, the window used for escape must provide a sufficient opening so a person can exit safely in an emergency. The required minimum is 0.35 square metres of net clear opening. Net clear opening means the part of the window that can actually be opened and passed through, measured without including the frame or any hardware that reduces usable area. If the opening is smaller than this, it wouldn’t meet the escape requirements, which is why 0.35 m² is the standard minimum. Larger openings, like 0.50 or 0.75 m², would of course also work, but they aren’t required—the minimum is the important threshold.