When Approved Document B's prescriptive guidance doesn't fit, fire engineering provides innovative, evidence-based solutions. We explore the approach.. Beyond Prescriptive Compliance For buildings over 18m, complex geometries, or innovative designs, prescriptive guidance in Approved Document B often cannot be directly applied. Fire engineering provides a rational, evidence based alternative. When Fire Engineering Is Needed Extended travel distances — open plan offices, large retail spaces Atria and open volumes — shopping centres, airports, cultural buildings Reduced staircase provision — where operational requirements limit options Novel building designs — curved facades, bridges between towers Mixed use buildings — combining residential, commercial, and leisure The Fire Engineering Process 1. Qualitative Design Review (QDR) — stakeholder workshop to define fire scenarios 2. Fire scenario analysis — deterministic and probabilistic approaches 3. CFD modelling — FDS simulation of smoke and heat 4. Evacuation modelling — Pathfinder, STEPS, or Exodus 5. Structural fire analysis — Eurocode fire calculations 6. Comparative analysis — demonstrating equivalent or superior safety 7. Third party peer review — independent verification of analysis Case Study: 22 Bishopsgate London's tallest office tower required extensive fire engineering: Performance based approach to escape stairway sizing CFD modelling of sky lobbies and atrium spaces Phased evacuation strategy for 12,000+ occupants Innovative refuge areas with structural fire protection Full scale evacuation drill protocol For fire engineering consultancy, contact Magnus Opifex.