Choosing the route before you start
The single most consequential decision in a fire strategy is which document you are designing to, and it has to be made at the start. Changing route halfway produces a strategy that satisfies neither, and that is exactly what a reviewer picks up.
In England there are broadly four routes:
- Approved Document B. Prescriptive, well understood, deemed to satisfy. The default for buildings that fit the guidance.
- BS 9991 (residential) or BS 9999 (non-residential). Alternative published routes with more design freedom, particularly BS 9999's risk-profile method.
- BS 7974 and the PD 7974 series. Performance-based fire safety engineering, for buildings the prescriptive guidance cannot serve.
- A hybrid. Prescriptive throughout with specific, individually justified departures analysed to PD 7974. In practice this is the most common route on complex buildings.
Our which standard applies tool takes the building parameters and gives you a reasoned recommendation, and the guide explains the reasoning behind it.
Do not mix routes within a single system. Taking BS 9999's extended travel distances while relying on ADB's smaller exit widths is not a hybrid design, it is an incoherent one. Each document's provisions are calibrated against the rest of that document. Mix at the system boundary, never inside it.
The documents
| Document | Applies to | What it does |
|---|---|---|
| Approved Document B 2019 edition incorporating the 2020, 2022 and 2025 amendments, collated with the 2026 and 2029 amendments |
Volume 1 dwellings, Volume 2 buildings other than dwellings | The default prescriptive route in England. Meeting it is deemed to satisfy Requirement B of the Building Regulations. Guidance, not law. The requirement is B1 to B5; the Approved Document is one way of meeting them. The 2026 amendments take effect 30 September 2026 and the 2029 amendments on 2 September 2029; transitional provisions keep the previous edition in play for applications made before each date, so check which edition your scheme falls under rather than assuming the latest. |
| BS 9991 2024, with amendment 2025 |
Residential buildings | Fire safety in the design, management and use of residential buildings. The 2024 revision brought in the second staircase provisions and substantially expanded evacuation guidance. An alternative to ADB Volume 1, not a supplement to it. Choose one route and apply it consistently. |
| BS 9999 2017 |
Non-residential buildings | A risk-based approach using risk profiles built from occupancy characteristic and fire growth rate, allowing extended travel distances and reduced widths where the risk profile justifies it. More design freedom than ADB Volume 2, and more analysis to produce and to defend. |
| BS 7974 2019 |
Any building | The framework for applying fire safety engineering principles: the performance-based route, used where prescriptive guidance cannot deliver the design. The framework only. The calculation methods sit in the PD 7974 series beneath it. |
| PD 7974 series Parts 1 to 7 |
Sub-systems of a fire engineering analysis (Parts 1 to 6), plus probabilistic risk | Part 1 initiation and development, Part 2 smoke and toxic gas spread, Part 3 structural response, Part 4 detection and activation of fire protection systems, Part 5 fire and rescue service intervention, Part 6 occupant evacuation, behaviour and condition (the human factors part that carries ASET/RSET). Part 7 is probabilistic risk assessment and sits outside the six sub-systems. Published Documents supporting BS 7974. This is where the equations live. |
| PAS 9980 2022 |
Existing multi-storey residential external walls | Code of practice for the fire risk appraisal of external wall construction: the FRAEW methodology. Produces a reasoned risk rating, not a pass or fail. |
| BR 187 2nd edition |
External fire spread between buildings | Space separation: boundary distance, unprotected areas, view factors and the 12.6 kW/m² radiation criterion. Both tables and the underlying analytical method. The calculation often permits less separation than the tables. |
| CIBSE Guide E Fire Safety Engineering |
Building services and fire | Smoke control, ventilation, detection, suppression and the interaction between fire safety and building services design. The practical companion to the standards for anything mechanical or electrical. |
| BS EN 13501 Parts 1 and 2 |
Classification | Part 1 reaction to fire: the Euroclass A1 to F system. Part 2 fire resistance: the R, E and I classifications. Classification standards. They tell you what a rating means, not what rating you need. |
| BS 9997 / BS 9990 / BS 5839 Various |
Management and systems | BS 9997 fire risk management systems, BS 9990 non-automatic firefighting water supplies, BS 5839 fire detection and alarm systems. The system standards a strategy references rather than reproduces. |
| Building Safety Act 2022 2022, with regulations from 2023 |
England, higher-risk buildings | The Gateway regime, dutyholder duties, the golden thread, the accountable person and the safety case. Primary legislation. Unlike the Approved Documents, this is not optional guidance. |
| Fire Safety Order 2005 As amended by the Fire Safety Act 2021 and the Building Safety Act 2022 |
Occupied non-domestic premises and common parts | The fire risk assessment duty on the responsible person during occupation. Occupation-stage law. It is what the design has to be manageable under. |
Scotland, Wales and Northern Ireland
The framework above is England. The devolved administrations differ in ways that matter:
- Scotland uses the Building Standards system and the Technical Handbooks, Domestic and Non-domestic. Different structure, different provisions, and the Approved Documents have no standing.
- Wales uses Approved Document B but has diverged in several respects, including sprinkler requirements in new residential buildings.
- Northern Ireland uses its own Technical Booklet E.
- The Building Safety Act Gateway regime applies in England only. This catches people out on portfolio work.
Editions and why they matter
A fire strategy that cites a standard without its edition and date is defective. Standards are revised, provisions move between clauses, and a design justified against a superseded edition is a design justified against nothing.
Every guide and calculator on this site states the edition it relies on and the date it was last reviewed. Check the current published edition before relying on any of it, including ours.