Fire Safety in Commercial Buildings

What This Requirement Covers

Approved Document B Volume 2 covers fire safety in buildings other than dwellings, including offices, shops, factories, assembly buildings, and mixed-use developments. Requirements are determined by the building's purpose group, height, and floor area.

The Regulatory Reform (Fire Safety) Order 2005 also places ongoing duties on the Responsible Person to maintain fire safety in non-domestic premises.

Key Requirements

Purpose Groups

Non-domestic buildings are categorised by purpose group, which determines fire resistance, compartmentation, and escape provisions

1. Group 2 (Residential institutional): Hospitals, care homes, prisons
2. Group 3 (Other residential): Hotels, hostels, boarding houses
3. Group 4 (Office): Offices, business premises
4. Group 5 (Shop and commercial): Shops, restaurants, pubs, showrooms
5. Group 6 (Assembly and recreation): Theatres, cinemas, sports facilities
6. Group 7 (Industrial): Factories, workshops
7. Group 8 (Storage): Warehouses, car parks

Means of Escape

1. Maximum travel distances depend on the purpose group and whether more than one escape route is available:

- Offices: 18 m (one direction) or 45 m (more than one direction) - Shops: 18 m (one direction) or 45 m (more than one direction) - Assembly: 15 m (one direction) or 32 m (more than one direction) - Storage/industrial: 25 m (one direction) or 45 m (more than one direction)

1. Exit widths are calculated based on the number of occupants, using the capacity factors in Table C1
2. A minimum of two escape routes from any storey with an occupancy exceeding 60 persons
3. Escape stairs must be protected stairways (minimum 30 or 60 minutes fire resistance depending on building height)

Compartmentation

1. Maximum compartment sizes are set by purpose group and building height (Table 12.1):

- Office, over 18 m: 4000 m² per floor - Shop, single storey: 2000 m² per floor (no sprinklers) or unlimited (with sprinklers) - Storage/industrial: 2000-14000 m² depending on height and sprinkler provision

1. Sprinklers can double the permitted compartment size in many categories

Fire Detection and Alarm

1. A fire detection and alarm system to BS 5839-1 is required in most non-domestic buildings
2. The category (L1, L2, L3, M, or P) depends on the building type and risk assessment:

- Category M: Manual call points only (offices and shops with simple layouts) - Category L2: Automatic detection in specified areas (buildings with sleeping accommodation) - Category L1: Full automatic detection throughout (high-risk premises)

Exceptions and Exemptions

1. Small detached buildings under 30 m² and more than 1 metre from a boundary may have reduced fire resistance requirements
2. Open-sided car parks have specific relaxations due to natural ventilation
3. Sprinkler-protected buildings may benefit from relaxed compartmentation and extended travel distances
4. Fire-engineered solutions using BS 7974 may depart from prescriptive guidance where justified

Practical Compliance Tips

1. Carry out a detailed fire strategy early in the design process, particularly for mixed-use buildings
2. Calculate occupancy figures for each room and floor to determine exit widths and number of escape routes
3. Coordinate fire compartmentation with the structural and services design to avoid late-stage conflicts
4. Ensure emergency lighting, fire signage, and fire-fighting equipment are included in the specification
5. The fire safety order requires a written fire risk assessment before the building is occupied; plan for this during handover
6. Automatic fire suppression can provide significant design flexibility; consider sprinklers even where not mandatory
7. Buildings with complex escape strategies (phased evacuation, progressive horizontal evacuation) require a detailed management plan