What Is Approved Document B?

Approved Document B is the official guidance that tells you how to meet the fire safety rules in Part B of the Building Regulations in England. It covers five areas: warning and escape, surface spread of flame, structural fire resistance and compartments, external fire spread, and fire service access. It comes in two volumes, one for homes and one for everything else. For owners and managers, it matters long after construction, because it is the yardstick used to judge whether a building’s fire protection is still adequate.

If you own, let or manage a building in England, you don’t need to read Approved Document B cover to cover. You do need to know what it expects, which version applies to you, and where buildings tend to fall short once the contractors have gone. This guide covers each of those. For a more technical look at the document itself, see our complete guide to Approved Document B.

Is Approved Document B a Rule or a Recommendation?

It sits in between. The legal duty comes from the Building Regulations 2010. Approved Document B is the government’s practical guidance on how to meet them. Following it is not compulsory, and you can take a different route if you can show it achieves the same level of safety. In practice, most designers, building control bodies, insurers and fire risk assessors treat it as the default standard.

Follow the Fire: The Five Parts of Part B

The easiest way to understand Approved Document B is to follow a fire as it develops. Each requirement answers one question.

B1: Can people get out? This covers fire detection and alarms, the width and length of escape routes, protected stairways and exit doors. It is about giving occupants warning and a safe way out.

B2: Will the surfaces help the fire spread? Wall and ceiling linings can carry flames quickly across a room. B2 limits this by controlling how linings and certain plastics behave in fire.

B3: Will the building hold and keep the fire contained? The structure must stay standing for a set period, and the building is divided into fire-resisting compartments. Every opening through those walls and floors, such as doors, ducts and service routes, must be protected. This is the part that most depends on installation quality and on upkeep over the years, so it is where owners most often find problems.

B4: Can fire spread from the outside? This looks at external walls, roofs and the distance to neighbouring buildings, to stop a fire jumping between floors or between buildings.

B5: Can the fire service do their job? This covers vehicle access, water supplies, fire mains and firefighting shafts in taller buildings.

Two Volumes, One Building: Which Applies?

Approved Document B is published in two parts. Volume 1 covers dwellings, including flats and the shared areas of residential blocks. Volume 2 covers all other buildings, such as offices, shops, warehouses, schools, hotels and care homes.

Mixed-use buildings are where this gets interesting. Picture a block with a shop and an office on the ground floor and flats above. The commercial space is judged against Volume 2, the homes against Volume 1, and the fire separation between them has to satisfy both. Working out how the two fit together is a job for a competent fire engineer, not a rule of thumb.

What Has Changed, and What’s Coming

Approved Document B is being updated in stages, and the Building Safety Regulator now oversees the process.

• 2 March 2025 (in force): Regulation 38 was tightened so fire safety information is handed to the responsible person at completion. The phase-out of the old British Standard (BS 476) national fire classifications in favour of European (BS EN 13501) classes began. Sprinklers became required in all new care homes.
• 30 September 2026 (now in force): New residential buildings in England with a storey 18 metres or more above ground level must have a second staircase. Interlocked or scissor stairs don’t count as two. Evacuation shafts and revised fire door provisions were also introduced. Projects that already had building control notices or full plans in before that date can still follow the earlier guidance, provided the work is sufficiently progressed by 30 March 2028. The change does not apply to existing buildings.
• 2029: The remaining national classifications are due to be withdrawn, completing the move to European classes.
• Beyond: A wider review of the document is under way, and the Building Safety Regulator has consulted on proposed revised text. Expect further change.

If you have a project in the pipeline, ask your design team which edition it is being assessed against.

After Handover: How Approved Document B Is Used in Existing Buildings

Approved Document B is written for new work, extensions and changes of use. But once a building is occupied, the safety duty moves to the responsible person under the Regulatory Reform (Fire Safety) Order 2005, and the fire risk assessment becomes the main tool. Assessors, insurers and fire officers still refer back to the Approved Document when judging whether compartmentation, fire doors and fire dampers are good enough.

You are not expected to rebuild an older building to today’s edition. But where protection has been damaged, removed or was never installed properly, the document is the benchmark for working out what’s wrong and how to fix it.

For multi-occupied residential buildings over 11 metres, there is an extra duty. Since January 2023, the Fire Safety (England) Regulations 2022 have required quarterly checks of communal fire doors and annual checks of flat entrance doors (on a best-endeavours basis).

A Practical Checklist for the Responsible Person

• Do you hold the fire safety information from the original build, and is it up to date?
• Is your fire risk assessment current, and does it look at compartmentation, not just alarms and extinguishers?
• Have service penetrations (pipes, cables, ducts) been re-sealed after every maintenance job?
• Are fire doors closing fully, with seals and closers intact?
• Are fire dampers accessible, recorded and checked on a schedule?
• Has any refurbishment altered walls, ceilings or risers without fire stopping being recorded?
• If the building has changed use or been extended, has the applicable volume been checked?

A “no” or “don’t know” to any of these is a good reason to arrange a survey.

How Meritas Can Help

Meritas is an independent passive fire protection consultancy working with owners, landlords and facilities teams across the East of England. We survey and repair fire compartmentation, and carry out fire damper and fire door work and fire risk assessments, so what’s installed in your building matches what Approved Document B expects. Contact us to book a survey.