Approved Document B: Fire Safety Rules and 2026 Changes

Approved Document B is the government’s official guidance on how to meet the fire safety requirements of the Building Regulations 2010 in England. It translates five broad legal duties, labelled B1 through B5, into practical technical solutions covering warning and escape, internal linings, structural fire resistance, external fire spread, and fire service access.¹ The guidance comes in two volumes, one for dwellings and one for every other kind of building, and it is being significantly updated in 2026 with new rules on second staircases and evacuation lifts in taller residential blocks.²

Guidance, Not Law

A point worth getting straight at the outset: Approved Document B is not itself the law. The legal requirements sit in Schedule 1 of the Building Regulations 2010, and they are written as outcomes rather than instructions. B1, for example, simply requires a building to provide “appropriate means of escape in case of fire.”¹ Approved Document B describes one accepted way to meet that outcome. Follow it and you can be confident of compliance. You are free to use another approach, such as a fire-engineered design, provided you can show it satisfies the same functional standard. Most projects stick with the approved document because any departure shifts the burden of proof onto the designer.

The guidance applies to most building work in England: new construction, major renovations, extensions, and changes of use where a building’s purpose shifts, such as converting an office into flats.³ Wales publishes its own edition through the Welsh Government, so this document does not carry across the border.⁴

The Five Fire Safety Requirements

Every technical section in the document ties back to one of the five functional requirements in Schedule 1.¹

B1 – Warning and escape. Early warning of fire and a safe route to a place of safety outside the building.
B2 – Internal linings. Wall and ceiling linings that resist flame spread and release heat at a reasonable rate if they ignite.
B3 – Internal fire spread (structure). Structural stability for a reasonable period in a fire, fire-resisting party walls between adjoining buildings, and cavity design that prevents hidden fire and smoke travel.
B4 – External fire spread. External walls and roofs that resist fire spreading across their surfaces or to neighbouring buildings, taking account of height, use, and position.
B5 – Fire service access. Facilities inside the building and access on the site that let firefighters reach the fire and operate safely.

Both volumes of the document address all five, but the technical solutions differ depending on what kind of building you are working on.⁵

Volume 1: Houses and Flats

Volume 1 covers buildings where people sleep. That fact drives the guidance: because occupants may be asleep when a fire starts, detection needs to be earlier and escape routes need to be better protected than in a workspace used only during the day.

For B1, smoke alarms are required on every storey containing a habitable room, typically in hallways and on landings. Houses generally rely on a protected stairway enclosed by fire-resisting construction so residents can reach the front door without passing through a smoke-filled room. In flats served by a common corridor, the corridor is fire-separated from individual units and travel distances to a stairway are capped.

B2 sets minimum classifications for how quickly flame can spread across wall and ceiling surfaces, with stricter ratings in escape routes and communal areas than inside individual rooms. Under B3, a typical two-storey house needs 30 minutes of fire resistance for its floors and load-bearing walls; taller residential buildings need 60 minutes or more, with the period increasing alongside height. Party walls between terraced or semi-detached houses must resist fire spread between the separate dwellings, and cavity barriers inside wall and floor voids stop smoke and flames travelling unseen through the structure.

B4 controls external spread through separation distances and material choice. Since the Grenfell Tower fire in 2017, the government has banned combustible materials in the external walls of residential buildings over 18 metres.⁶ B5 in most houses means a clear driveway and access to a water supply; in blocks of flats it can require dry or wet rising fire mains, firefighting lifts, and designated firefighting shafts.

Volume 2: Everything Else

Volume 2 covers shops, offices, factories, warehouses, hospitals, schools, and every other non-dwelling. The same B1 through B5 framework applies, but the solutions scale up because these buildings are larger, hold more people, and often house occupants unfamiliar with the layout.⁷

B1 in a commercial setting usually means an integrated fire alarm system rather than standalone detectors, along with emergency lighting across the full floor plan. Travel distances vary by the risk profile of the space, so a low-risk office gets more distance than a high-risk storage area. Buildings open to the public face additional scrutiny on signage, corridor widths, and door hardware, because visitors have never walked the layout before.

Compartmentation under B3 is more demanding. Large floor areas must be subdivided by fire-resisting walls and floors into compartments that contain a fire long enough for evacuation and firefighting, with maximum compartment sizes tied to use and height. Warehouses storing hazardous or high-fuel-load goods face stricter limits. Smoke control systems, whether mechanical extraction or natural ventilation, keep corridors and stairs clear during evacuation. Taller commercial buildings and those with deep basements need firefighting lifts and fire mains under B5, because the fire service cannot rely on ground-level hose runs many storeys up.

What’s Changing in 2026

The 2026 amendments introduce some of the most significant fire safety changes since the post-Grenfell reforms. They take effect on 30 September 2026.⁷

Second Staircases in Tall Residential Buildings

New residential buildings with a storey at 18 metres or above must be designed with more than one common staircase, so residents have another way out if one becomes impassable. Interlocked or scissored stairs count as a single stair for this purpose and will not satisfy the requirement on their own.⁷

A transitional period applies. Projects with a building control application submitted before 30 September 2026 are exempt, provided construction has started and is sufficiently progressed by that date or within 18 months after it. For a new building, “sufficiently progressed” means permanent foundation work has begun: concrete pouring for trench, pad, or raft foundations, or permanent piling.

Evacuation Lifts

The amendments also add design provisions to support evacuation lifts in blocks of flats. These lifts are specifically designed to help residents leave during a fire, a shift away from a pure “stay put” approach that relied on compartmentation alone.⁷

Sprinklers in Care Homes

Since March 2025, all new care homes in England must install sprinkler systems regardless of height. The previous threshold was 30 metres. The change reflects the difficulty care home residents face evacuating without substantial assistance.

Higher-Risk Buildings and the Gateway Process

The Building Safety Act 2022 created a separate regulatory regime for higher-risk buildings. A building qualifies if it is at least 18 metres tall or has at least 7 storeys, contains at least 2 residential units, and is not a prison, hotel, or military barracks.⁸ Hospitals and care homes are included for design and construction but excluded from the ongoing in-occupation duties.

If your project is a higher-risk building, you do not choose your building control body. The Building Safety Regulator, part of the Health and Safety Executive, is the sole authority.⁹ The project must pass through three gateways before anyone moves in.

Gateway 1 (planning). The fire safety strategy is built into the planning application, including the escape strategy, fire spread prevention, fire service access, and compliance with the second staircase requirement where it applies.
Gateway 2 (before construction). The Building Safety Regulator reviews and approves the full detailed design before any work starts on site. That means a complete fire safety case, structural fire protection specifications, smoke control designs, and evidence that the principal designer and principal contractor are competent.
Gateway 3 (before occupation). The regulator inspects the finished building and checks that what was built matches what was approved. All fire safety systems must be commissioned and operational before the building can be occupied.

A “golden thread” of safety information must be maintained from design through construction and into the building’s operational life, creating a permanent record of every safety-critical decision and material choice. Most developers find this the most demanding part of the new regime, because it requires disciplined documentation throughout rather than a single submission at the end.

Building Control for Everything Else

For buildings that are not higher-risk, you still have a choice of building control body. You can submit to the local authority building control department, or you can appoint a registered building control approver, the term that replaced “approved inspector” under the Building Safety Act 2022.¹⁰

You submit plans and fire safety documentation for review. Once approved, inspectors visit the site at key construction stages to check the work matches the design. They pay particular attention to elements that will be hidden once the building is finished: cavity barriers inside wall voids, fire-stopping around pipe penetrations and ventilation ducts, and the integrity of compartment walls at junctions with other building elements. A completion certificate is issued once the inspector is satisfied, and that certificate serves as legal proof the building complies.

Complex buildings and those with multiple occupancies usually also need a written fire safety strategy that explains how the detection system, compartmentation, escape routes, smoke control, and fire service access provisions all work together, and how the building will be managed after completion.

What Happens If You Don’t Comply

Local authorities have several enforcement tools, and the Building Safety Act made them substantially tougher.¹¹

Compliance notice. Can be issued within 12 months of a contravention, requiring you to bring the work into line.
Section 36 notice. The local authority can require you to pull down or alter non-compliant work. The time limit for these notices was extended from 12 months to 10 years after completion.
Section 35 prosecution. No time limit on prosecution. Penalties now include unlimited fines and up to two years of imprisonment.

Appeals against a Section 35 or 36 notice must be lodged within 21 days. Beyond formal enforcement, failing to obtain a completion certificate creates practical problems of its own: mortgage lenders may refuse to lend against the property, insurers may decline cover, and selling becomes considerably harder. The ten-year window on removal notices means non-compliant work can catch up with a building owner long after the contractor has moved on.

After the Building Is Occupied

Approved Document B governs design and construction. Once people move in, a separate regime takes over. The Regulatory Reform (Fire Safety) Order 2005 places ongoing duties on a “responsible person” for most non-domestic premises and the common areas of residential buildings, typically the employer, building owner, landlord, or managing agent. They must carry out and regularly review a fire risk assessment, maintain detection and suppression systems, keep escape routes clear, and provide fire safety training where applicable. The local fire and rescue authority enforces these duties and can issue enforcement or prohibition notices where it finds serious deficiencies.

The practical consequence is that a building designed to Approved Document B still needs active management to stay safe. Propped-open fire doors, disabled smoke detectors, blocked escape routes, and neglected sprinkler systems can all undo the original design. For higher-risk residential buildings under the Building Safety Act, these ongoing responsibilities are more structured still, with a named accountable person and mandatory safety case reviews throughout the building’s life.

1
Legislation.gov.uk. The Building Regulations 2010 – Schedule 1
2
GOV.UK. Fire Safety: Approved Document B
3
Legislation.gov.uk. The Building Regulations 2010
4
Law Wales. Building Regulations
5
Planning Portal. Approved Document B – Volume 1: Dwellings
6
GOV.UK. Review of the Ban on Combustible Materials
7
GOV.UK. Approved Document B Volume 2 – Buildings Other Than Dwellings
8
GOV.UK. Definition of Higher-Risk Buildings: Initial Review and Plans for Ongoing Review
9
GOV.UK. Building Control Regime for Higher-Risk Buildings (Gateways 2 and 3)
10
GOV.UK. Consultation for Changes to the Building Control Profession and the Building Control Process for Approved Inspectors
11
Planning Portal. Failure to Comply With the Building Regulations