Fire and Life Safety: Egress, Fire-Resistive Construction, Sprinklers, and Wildfire/WUI
Egress in five steps
CBC Chapter 10 asks: what is the occupant load (Table 1004.5 - 150 gross for business, 60 gross for mercantile, 15 net for unconcentrated assembly, 20 net for classrooms); how many exits (one up to 49 occupants, two up to 500, four beyond); how wide (0.2 in per occupant for stairs and 0.15 in for other components, subject to minimums such as 44 in stairs and 32 in clear at doors); how far (commonly 200 ft unsprinklered and 300 ft sprinklered for Group B, measured along the path of travel); and where the exit discharges (at least half must discharge directly outside).
Passive and active protection
Construction Types I through V set structural fire resistance. Chapter 7 controls fire walls, shafts, opening protectives, and separations. Chapter 9 requires sprinklers per NFPA 13, 13R, or 13D based on occupancy, height, and area. Chapter 4 adds high-rise and atrium rules.
Wildland-urban interface
CBC Chapter 7A applies to new buildings in state responsibility areas and in local very-high fire hazard severity zones. It requires ignition-resistant exterior construction: Class A roofing, ignition-resistant wall coverings, protected eaves and underfloor areas, ember-resistant attic vents, tempered glazing where required, and compliant decking.
Worked example
A 12,000 sf Group B office: 12,000 / 150 = 80 occupants. Two exits are required. Calculated width is 80 x 0.15 = 12 in and 80 x 0.2 = 16 in in stairs - far below the code minimums, so the 32 in clear door and 44 in stair minimums govern.
Traps
Using gross area where net applies; forgetting the 50 percent exit-discharge rule; assuming Chapter 7A applies only in CAL FIRE state responsibility areas.