Approved Document B explained

What is Approved Document B?

Approved Document B is the statutory guidance showing one way to meet the fire safety requirements B1 to B5 of the Building Regulations 2010 in England. The current version is the 2019 edition incorporating the 2020, 2022, 2025 and 2026 amendments, and the biggest recent change is that new blocks of flats with a top storey of 18m or more should now have more than one common stair.

Approved Documents are published by the Ministry of Housing, Communities and Local Government (MHCLG). They are not law in themselves. The law is the functional requirement in Schedule 1 to the Building Regulations 2010, plus related regulations. Following the Approved Document creates a presumption of compliance, but the requirement can be met another way if compliance can be demonstrated, for example through a fire engineered approach.

ADB supports Part B of Schedule 1 and regulations 6(3), 7(2) and 38. It applies in England only; Wales, Scotland and Northern Ireland have their own guidance. Since April 2023 the Building Safety Regulator has had a duty to keep building standards under review, which is why ADB has changed several times in quick succession.

Following the guidance is one route to compliance. Showing how you complied is now the part that gets scrutinised.

Volume 1 vs Volume 2

Volume 1 covers dwellings, including houses and blocks of flats. Volume 2 covers every other building type. Mixed-use schemes apply each volume to the part of the building it governs.

Both volumes are published together on GOV.UK as the 2019 edition incorporating the 2020, 2022, 2025 and 2026 amendments, collated with the 2029 amendments that are not yet in force.

What requirements B1 to B5 cover

Part B sets five functional requirements. Each volume then works through them in sections, with appendices on performance classifications, fire doorsets and methods of measurement.

Building height in ADB is measured using Diagram D6, which takes the height of the top storey floor above ground level. Most of the recent amendments hang off that measurement.

What changes at 11m and 18m

For blocks of flats, two heights do most of the work. Above 11m, sprinklers, wayfinding signage and secure information boxes come in. Above 18m, a second common stair, evacuation alert systems and the regulation 7(2) materials ban are added.

What does regulation 7(2) require?

Regulation 7(2) is the combustible materials ban introduced by the Building (Amendment) Regulations 2018, in force from 21 December 2018. It applies to "relevant buildings": those with a storey at least 18m above ground (measured using Diagram D6) that contain one or more dwellings, an institution or a room for residential purposes. Materials that become part of an external wall or specified attachment must achieve class A2-s1, d0 or class A1 under BS EN 13501-1, unless exempted by regulation 7(3).

Below 18m, ADB still restricts materials. In residential buildings with a storey of 11m or more, Volume 1 para 10.7 recommends that insulation products and fillers in the external wall are class A2-s1, d0 or better.

How ADB has changed since 2020

ADB has been amended five times since the 2019 consolidated edition, with a sixth set already published for 2029. Quoting a paragraph from the wrong layer is now one of the easiest fire safety errors to make.

2020: sprinklers and wayfinding

The May 2020 amendments took effect on 26 November 2020. They lowered the sprinkler trigger in new blocks of flats from 30m to 11m (Volume 1 para 7.4) and introduced floor identification and flat indicator signs for the fire service.

2022: information boxes, alert systems and the MCM ban

The June 2022 amendments took effect on 1 December 2022. They added secure information boxes in blocks over 11m (para 15.19), evacuation alert systems to BS 8629 in blocks over 18m (para 15.17), a ban on relevant metal composite material in external walls at any height under regulation 7(1A), and updated guidance on regulation 7(2), including balconies and solar shading.

2025: care homes and reaction to fire classes

The 2025 amendments took effect on 2 March 2025, with a six-month transition. New care homes should have sprinklers throughout (Volume 2, para 2.46), the BS 476 national classes for reaction to fire were removed in favour of BS EN 13501, and the regulation 38 fire safety information guidance was replaced. The 2029 amendments will do the same for fire resistance classes from 2 September 2029.

The 18m second staircase rule

Since 30 September 2026, Volume 1 para 3.30 says flats should be served by more than one common stair where the building has a top storey of 18m or more, or where a flat does not meet the single escape route or small single stair criteria.

The same 2026 amendment booklet makes several related changes:

• Interlocked (scissor) stairs count as a single escape route, not two (para 3.31).
• Stair width: common stairs in buildings with a storey of 18m or more, and firefighting stairs, should be at least 1100mm clear.
• Evacuation lifts, where provided, sit in an evacuation shaft with a protected stairway and evacuation lift lobby.
• Travel distances in Table 3.1 for common areas: 7.5m in one direction, 30m in more than one, 4.5m for small single stair buildings.

The small single stair route in para 3.32 remains, but only where the top storey is no more than 11m above ground and there are no more than three storeys above the ground storey.

How the transition period works

The previous version still applies where a building notice, initial notice or full plans application was given before 30 September 2026, and the work is sufficiently progressed before that date or within the following 18 months.

A single-stair scheme check

• ✓The application date is recorded and was before 30 September 2026.
• ✓Top storey height is measured to Diagram D6, not taken from a planning drawing.
• ✓The programme shows foundation concrete or piling before the end of March 2028.
• ✓The client knows the redesign risk if that date slips.
• ✓Stair widths, lifts and travel distances are checked against the version that will actually apply.

If foundations by March 2028 look unlikely, the redesign conversation is better had now than at stage 5. Many of these buildings are also higher-risk buildings, where the Building Safety Regulator is building control and full plans must show Part B compliance before work starts.

Where Avoice fits

ADB is long, heavily cross-referenced and now has several amendment layers. Most errors come from quoting a superseded paragraph or missing a provision that applies above a height trigger.

Avoice Regulations is a searchable library of the England Approved Documents, the Building Regulations 2010 and the Building Safety Act regime. Teams can read the full Approved Document B and ask questions that come back with citations showing whether the answer comes from legislation or statutory guidance. Inside Avoice Practice, the Building Regs Tracker records which Part B provisions apply to each project and where compliance is evidenced.

Software can retrieve, compare and flag. The fire engineer, the architect and building control still decide what the project requires and whether the evidence is adequate.