Coffee Break Training: Access and Water Supplies: Fire Flow Formulas: Part 18: 'International Fire Code' Fire Flow Requirements for Buildings [open pdf - 559KB]
"IFC [International Fire Code®] Appendix B, Fire-Flow Requirements for Buildings, provides another method for computing the required fire flow for buildings. The IFC method employs a table that lists the minimum flow based on the 'International Building Code®' construction type and size of the structure, or what is called the 'fire flow calculation area.' The fire flow calculation area is the sum of all floor area between firewalls with no openings or, in fire-resistive construction, the sum of the area of the three largest successive floors."
Coffee Break Training - Fire Protection Series No. FP-2014-1
United States Fire Administration: http://www.usfa.fema.gov/