High-rise residential fire engineering has transformed since Grenfell. This masterclass covers second staircases, sprinkler mandates, evacuation strategies, and BSR requirements for towers over 18 metres.. The New Era of High Rise Fire Safety Since the Grenfell Tower tragedy in 2017, fire engineering for high rise residential buildings in the UK has undergone a complete transformation. The Building Safety Act 2022, combined with regulatory reform and industry culture change, has created a new paradigm for designing, constructing, and managing tall residential buildings. Regulatory Framework for HRBs Building Safety Act 2022 Higher Risk Buildings (HRBs) : residential buildings 18m+ or 7+ storeys Gateway process : three stage approval by the Building Safety Regulator Safety case : mandatory safety case report for all occupied HRBs Golden thread : comprehensive digital building information record Mandatory occurrence reporting : structural failures, fire events, safety system faults Approved Document B (2024 amendments) Second staircases : mandatory for residential buildings over 30m Sprinklers : mandatory for residential buildings over 11m Combustibility ban : non combustible materials for external walls above 18m Evacuation alert systems : BS 8629 compliant systems in all HRBs Second Staircase Design The requirement for a second staircase in buildings over 30m fundamentally changes floor plate design: Design Considerations Minimum stair width : 1,100mm clear width for each staircase Separation : maximum 180° apart in plan (ideally at opposite ends) Independence : fire rated separation between staircases throughout Ventilation : each staircase independently ventilated Firefighting access : one staircase designated as firefighting stair Signage : clear directional signage to both staircases Floor Plate Impact Building Height Stair Requirement Floor Plate Impact <18m Single stair Standard 18 30m Single stair (enhanced) +5% core 30 50m Two stairs +12 18% core 50m+ Two stairs (firefighting) +15 22% core Evacuation Strategy Stay Put The default strategy for UK residential high rise: Principle : fire contained within compartment of origin Reliance : on compartmentation, detection, and suppression Override : to simultaneous evacuation if compartmentation fails Communication : BS 8629 evacuation alert system for partial/full evacuation Simultaneous Evacuation Required when stay put cannot be sustained: Trigger : smoke in common areas, multiple flat fires, structural concerns Challenge : staircase capacity for full building evacuation Management : phased approach — fire floor first, then adjacent floors Timing : total evacuation time target < 60 minutes for tallest HRBs Sprinkler Systems BS 9251 Domestic Sprinklers Coverage : all habitable rooms and common areas Temperature rating : 68°C standard, 57°C in bedrooms Water supply : dedicated tank and pump or mains fed (pressure dependent) Flow rate : minimum 42 litres/min per head, 2 heads operating Maintenance : annual service by BAFSA accredited contractor Benefits Quantified 80% reduction in fire deaths 70% reduction in property damage 60% reduction in fire spread beyond room of origin 99.5% operational reliability when properly maintained Cost : £1,500 3,000 per apartment (new build) Facade and External Wall Combustibility Requirements (Regulation 7) Above 18m : all materials must achieve Class A1 or A2 s1, d0 Below 18m : risk based approach using BS 9414 assessment Assessment : full scale fire test to BS 8414 with BR 135 classification Cavity barriers : at every floor level and maximum 20m² cavities Common Facade Risks 1. Combustible insulation — replacing with mineral wool or PIR alternatives 2. Cavity bypass — fire spreading behind cladding through cavities 3. Balcony fires — BBQ ignition spreading to facade 4. Window spandrel — insufficient fire resistance between floor levels BSR Gateway Process Gateway 2 — What You Need Complete fire strategy report (BS 9999 or BS 9991) Structural fire engineering report CFD modelling results (if performance based approach) Product certification for all fire safety products Construction control plan Competence declarations for all duty holders Fire and emergency file Average review time : 16 20 weeks (statutory target: 12 weeks) Rejection rate : approximately 25% of first submissions Common rejection reasons : inadequate fire strategy detail, missing product certification, incomplete golden thread documentation Magnus Opifex SEVEN LTD — UK's Leading Fire Safety & Fire Engineering Consultancy 🌐 magnus opifex.co.uk 📞 +44 7486 691724 ✉️ office@magnus opifex.co.uk Founders: Nicoleta Vasile, Baroness of Brattleby — CEO, Lawyer and Barrister, Legal & Administrative Director Alina — Technical Director & Expert Fire Engineer (BEng) Head Office: Ealing Cross, 85 Uxbridge Road, London W5 5BW Magnus Opifex SEVEN LTD delivers engineering led fire engineering, fire risk assessments, CFD modelling, and building safety consultancy across th