Firewalls & Number of Exits Required for Each Fire Area

There has been an interpretation by some authorities having jurisdiction that when a building is divided into multiple smaller building areas/fire areas, each "separate building" bounded by firewalls requires at least one exit stair. The reasoning behind this interpretation is that every building requires a minimum of two exits and to avoid having two exit stair enclosures per building area, one of the "required" two exits may be a horizontal exit (the firewall which will have a 2-hour or 3-hour fire-resistance-rating based on the building construction type) and the second exit is required to be an exit stair enclosure since only 50% of exits are permitted to be horizontal exits.

This interpretation creates several unnecessary design challenges and over-design costs resulting from:

• more exit stairs than needed to satisfy travel distance, number of exits and exit capacity

• modifications/alternate approaches to share a single exit stair at the firewall boundary condition between two adjacent buildings

• loss of leasable or sellable floor area taken by the extra exit stair(s)

On July 29, 2014, the California State Fire Marshal (CSFM) issued a formal Code Interpretation that clarified that firewalls are primarily used to create "separate buildings" for the purpose of allowable area/construction type classification and not for meeting the egress requirements of the Code. Provided the firewalls are used in a building operated and functioning in all other respects as a single building (e.g., joint building services), the firewalls may be used for egress purposes. The CSFM clarifies that as long as the “separate buildings” constructed by fire walls are not being used as a horizontal exit and exit access travel distances are met, then the egress requirements are not be required to be independent of the rest of the “separate buildings.”

Should you run into a mis-interpretation of firewalls and egress requirements by a California approving agency, show them the CSFM Code Interpretation 14-00