Building and Safety Division - Window Retrofit

Planning Department approval, Building Permit and Inspections Required

2001 California Building Code, Volume 1

310.4 Access and Means of Egress Facilities and Emergency

Basements in dwelling units and every sleeping room below the fourth story shall have at least one operable window or door approved for emergency escape or rescue that shall open directly into a public street, public alley, yard or exit court.  The emergency door or window shall be operable from the inside to provide a full, clear opening without the use of separate tools.
Escape or rescue windows shall have a minimum net clear openable area of 5.7 square feet (0.53 m2).  The minimum net clear openable height dimension shall be 24 inches (610 mm).  The minimum net clear openable width dimension shall be 20 inches (508 mm).  When windows are provided as a means of escape or rescue, they shall have a finished sill height not more than 44 inches (1118 mm) above the floor.

For complete code requirements please read the C.B.C. 2001.

Do the math

At first glance, you might assume that a 20-in. by 24-in. window (A) would be acceptable for egress. Those dimensions would yield a net clear opening of only 3.3 sq. ft.
 

To achieve the required net clear opening of 5.7 sq. ft., a 20-in. wide window (B) would have to be 42 in. high.
 

Likewise, a 24-in. high window (C) would have to be 35 in. wide.