| Full title | Approved Document B: Fire safety. Volume 1: Dwellings. Volume 2: Buildings other than dwellings |
| Publisher | HM Government (Ministry of Housing, Communities and Local Government) |
| Legal basis | Building Regulations 2010, Schedule 1 Part B (requirements B1 to B5) and regulations 6(3), 7(2) and 38 |
| Current edition | 2019 edition incorporating 2020, 2022, 2025 and 2026 amendments, collated with the 2029 amendments |
| Status | Statutory guidance. Following it is one way to show compliance with Part B |
| Applies to | England. Wales and Scotland publish separate guidance |
What it covers
Approved Document B (ADB) gives guidance on the fire safety requirements of the Building Regulations 2010 in England. Volume 1 covers dwellings, including dwellinghouses and flats. Volume 2 covers all other buildings.
| Requirement | Subject |
|---|---|
| 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 |
Most of ADB deals with building design. For cabling, the relevant guidance is on protected power circuits, fire-stopping of service penetrations, cavity barriers and the external wall rules.
Protected power circuits
A protected circuit is an electrical circuit that is protected against fire. ADB gives the same guidance in both volumes.
| Guidance | Vol 1 (flats) | Vol 2 |
|---|---|---|
| Cables sufficiently robust | 3.50a | 5.29a |
| Cable routes carefully selected and/or physically protected where cables may be exposed to damage | 3.50b | 5.29b |
| Methods of cable support class A1 rated, with at least the same integrity as the cable. They should maintain circuit integrity and hold cables in place when exposed to fire | 3.50c | 5.29c |
| Cables achieve PH 30 classification to BS EN 50200 (incorporating Annex E) or an equivalent standard | 3.51a | 5.30a |
| Circuit passes only through parts of the building where fire risk is negligible | 3.51b | 5.30b |
| Circuit separate from any circuit provided for another purpose | 3.51c | 5.30c |
| Guidance on cables for large and complex buildings is in BS 5839-1, BS 5266-1 and BS 8519 | 3.52 | 5.31 |
ADB does not refer to BS 7671. In BS 7671:2018+A4:2026, Regulation 521.10.202 deals with supporting wiring systems so they are not liable to premature collapse in a fire.
Fire-stopping of cable penetrations
Every joint, imperfect fit and opening for services through a fire-separating element should be sealed with fire-stopping so the fire resistance of the element is not impaired (Vol 1 para 9.1, Vol 2 para 10.1).
| Guidance | Vol 1 | Vol 2 |
|---|---|---|
| Openings for pipes, ducts, conduits or cable through a fire resisting element: as few as possible, as small as practicable, and fire-stopped | 9.24b | 10.24b |
| Fire-stopping reinforced or supported by materials of class A2-s3, d2 or better where the unsupported span exceeds 100 mm, or where non-rigid materials are used (unless tested) | 9.25 | 10.25 |
| Proprietary, tested fire-stopping and sealing systems may be used. Not all suit every situation | 9.26 | 10.26 |
| Other materials: cement mortar; gypsum-based plaster; cement-based or gypsum-based vermiculite/perlite mixes; glass fibre, crushed rock, blast furnace slag or ceramic-based products; intumescent mastics | 9.27 | 10.27 |
| Further guidance: ASFP best practice guide and ASFP Red Book | 9.28 to 9.29 | 10.28 to 10.29 |
Cavity barriers and cables
| Guidance | Vol 1 (dwellinghouses) | Vol 2 |
|---|---|---|
| Openings in cavity barriers limited to listed items, including the passage of cables or conduits containing one or more cables | 5.24 | 9.17 |
| Cavity barriers fixed so they are not made ineffective by collapse of penetrating services in a fire, through failure of the supporting system or degradation of the service | 5.23b | 9.16b |
| Cavities over an undivided area exceeding 40 m in any direction have no size limit only if all listed conditions are met. Two of them are that supports and fixings in the cavity are class A1 (d) and that any electrical wiring is laid in metal trays or metal conduit (f) | Not applicable | 9.12d and f |
Volume 1 para 8.9 applies the dwellinghouse cavity barrier guidance (paras 5.21 to 5.24) to flats.
Cables and reaction to fire
- ADB does not set reaction to fire classes for cables. It does not refer to BS EN 13501-6, the cable classification standard.
- Wall and ceiling lining classes in ADB are to BS EN 13501-1.
- For external walls of relevant buildings, regulation 7(2) requires materials of class A2-s1, d0 or A1. Regulation 7(3) exempts electrical installations and fibre optic cables, among other items.
- The same exemption for electrical installations and fibre optic cables appears in the balcony guidance (Vol 1 para 10.10).
Cable reaction to fire classes for fixed installations are covered on the BS EN 13501-6 and EN 50575 pages.
Amendments and dates
| Amendment | Takes effect | Main changes |
|---|---|---|
| 2025 | 2 March 2025 | Regulation 38 and fire safety information. Removal of national classes for reaction to fire and roofs. Sprinklers in new care homes |
| 2026 | 30 September 2026 | More than one common stair in blocks of flats with a storey 18 m or more in height. Design provisions for evacuation lifts in blocks of flats |
| 2029 | 2 September 2029 | Removal of national classes for fire resistance. Appendix B replaced |
Each amendment has transitional provisions. The earlier text continues to apply where a building notice, initial notice or full plans application was made before the start date and the work is sufficiently progressed within the set period. For the 2026 amendments that period is 18 months (six months for the 2025 and 2029 amendments).
Wales and Scotland
- Wales: the Welsh Government publishes its own Approved Document B in two volumes, with amendment slips, including one applicable from 20 December 2025.
- Scotland: fire guidance is in Section 2 (Fire) of the Building Standards technical handbooks for domestic and non-domestic buildings. Revised handbooks apply to building warrant applications from 6 April 2026.
What it means in practice
- For protected power circuits, ADB’s guidance is cable classified PH 30 to BS EN 50200 (incorporating Annex E) or an equivalent standard. For large and complex buildings it points to BS 5839-1, BS 5266-1 and BS 8519.
- ADB’s guidance for protected circuits is class A1 rated cable supports that hold cables in place when exposed to fire.
- Keep penetrations through fire resisting walls and floors few and small, and fire-stop them, using a proprietary tested system or another material suited to the situation (Vol 1 9.26 to 9.27, Vol 2 10.26 to 10.27).
- Cables may pass through cavity barriers. Barriers should be fixed so that collapse of penetrating services in a fire is unlikely to make them ineffective.
- In external walls of relevant buildings, electrical installations and fibre optic cables are exempt from the class A2-s1, d0 or A1 requirement under regulation 7(3).