Approved Document B is the cornerstone of fire safety in UK building design. This comprehensive guide breaks down every section and explains practical compliance.. What Is Approved Document B? Approved Document B (ADB) provides statutory guidance on meeting the fire safety requirements of the Building Regulations 2010 (England). It covers: B1 : Means of warning and escape B2 : Internal fire spread (linings) B3 : Internal fire spread (structure) B4 : External fire spread B5 : Access and facilities for the fire service Volume 1: Dwelling Houses Applies to individual houses (not flats). Key requirements: Smoke alarms: at least one per storey on escape route Escape windows: opening area ≥0.33m² at min 450mm dimension Inner rooms: only permitted in certain configurations Loft conversions: protected stairway required for 3 storey houses Volume 2: Buildings Other Than Dwelling Houses Applies to all other buildings including flats. Key sections: Purpose groups — classify building by use (residential, office, shop, assembly, industrial, storage) Travel distances — maximum distances to nearest exit based on purpose group and risk profile Exit widths — calculated from occupancy using Table 4 flow rates Compartmentation — maximum compartment sizes and fire resistance periods External walls — combustibility requirements based on height and boundary distance Key Tables and Diagrams Reference Content Table A1 Specific provisions of test for fire resistance Table A2 Minimum fire resistance periods Table 4 Minimum exit widths Table 8 Maximum travel distances Diagram 9.1 Compartment walls and fire walls Table B4 Fire resistance of elements of structure When ADB Is Not Enough ADB provides minimum standards. Fire engineering to BS 7974 may be needed when: Building exceeds ADB scope (e.g., complex mixed use, very tall buildings) Client wants to deviate from prescriptive requirements Innovative design requires performance based justification Building is too complex for simple prescriptive compliance 2024 Amendments Recent updates include: Clarification of requirements for buildings 11 18m Enhanced guidance on external wall construction Updated references to British Standards Additional guidance on evacuation strategies for residential buildings For ADB compliance guidance, contact Magnus Opifex. 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 the United Kingdom and internationally. With over 20 years of combined experience and a UK portfolio spanning healthcare, residential and infrastructure, we bring truly engineered solutions with a personal touch. © 2026 Magnus Opifex SEVEN LTD. All rights reserved.