Massachusetts building code is based on the International Residential Code. The core numbers are:

  • Opening area: at least 5.7 square feet of clear opening, measured with the window open. Openings at or below grade can be 5.0 square feet.
  • Height and width: at least 24 inches of clear height and 20 inches of clear width.
  • Sill height: no more than 44 inches above the floor.
  • Window well: at least 9 square feet of floor area and 36 inches out from the wall. A well deeper than 44 inches needs a ladder or steps.

Your local building department has the final word on what applies to your house.

Egress window benefits

A legal bedroom

A basement room without an egress opening cannot be listed as a bedroom. With one, it can.

Safety

It is the second way out of the basement when the stairs are blocked.

Daylight

An egress window is much bigger than a standard basement window, and a properly built well lets real light into the room.

How to choose an egress window

Most existing basement windows do not pass. A typical basement slider of 32 by 16 inches has well under half the opening the code asks for. So an egress job usually means cutting the foundation opening larger, not just swapping the window.

Casement windows give the most clear opening for their size, because the whole sash swings out of the way. Sliders work too, but they need a wider opening to reach the same area. Before you choose, measure the clear opening the window gives when it is fully open, not the size of the frame.

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