Renovation of Historic Office Building with Mixed-Use Conversion

Case Study 2: Renovation of Historic Office Building with Mixed-Use Conversion

Scenario A 1928 12-story unreinforced masonry office building in downtown Boston is being adaptively reused as a mixed-use structure: ground-floor retail (restaurant/bar), floors 2–5 as boutique hotel, floors 6–10 as Class-A office space, and rooftop mechanical penthouse. Structural constraints prohibit major pipe routing through existing load-bearing walls, and historic preservation guidelines limit exterior modifications (e.g., no new fire department connections or large above-ground tanks). The project must comply with MA State Building Code 780 CMR and NFPA 13R (for hotel portions) and NFPA 13 (for office/retail), requiring careful hazard zoning.

Given Data

• Occupancy and Hazard Classification: Ordinary Hazard Group 2 (driven by restaurant kitchen hood system, grease ducts, and office server rooms — governing hazard per IBC Section 903.3.1.1)
• Area of the Most Demanding Zone: 4,850 ft² (combined open-plan office/server room on Floor 8, identified via hydraulic modeling as having longest pipe run and highest head loss)

Calculation Using the Fire Flow Rate Calculator’s empirical method aligned with NFPA 1142 Annex A and IBC Table 906.2 guidance:

• Ordinary Hazard Group 2 corresponds to a hazard factor of 0.10 gpm/ft² for total required fire flow estimation.
• Required Fire Flow Rate = 0.10 gpm/ft² × 4,850 ft² = 485 gpm
• Tool output: 485 gpm (no rounding needed; integer result)

Result and Decision The required fire flow rate of 485 gpm was used to size the retrofit fire pump (1,000 gpm @ 125 psi, selected for redundancy and future tenant flexibility) and verify adequacy of the existing 8-in. city main (verified field flow test yielded 720 gpm @ 52 psi static — sufficient after pressure loss analysis). Because vertical riser space was constrained, engineers installed a compact, UL-listed variable-speed fire pump controller to maintain precise pressure across all zones without oversized piping. Coordination with Boston Fire Department confirmed acceptance of the 485 gpm design basis, contingent on quarterly pump testing logs submitted electronically.

Lesson In renovation projects, the ‘most demanding zone’ may not align with the largest floor area—it’s defined by hydraulic performance, not just square footage; always validate zone selection with detailed pressure-loss modeling across the full system.