Approved Document B: A Practical Guide for Interior Designers

For many interior designers, fire safety is often deferred to the architect or fire engineer. However, under the Building Regulations 2010, any professional who specifies interior finishes, modifies floor plans, or alters door configurations shares a duty to ensure compliance. Approved Document B is the essential technical roadmap for these decisions.

Legal Duties & Liability: Why Designers Share Responsibility

Interior designers are increasingly recognised as dutyholders. Whether you are reconfiguring a layout or specifying bespoke joinery, you are responsible for ensuring your design does not compromise the building’s life safety systems. Failing to account for Approved Document B can result in retrospective remedial works, significant project delays, and potential liability under the Building Safety Act dutyholder roles.

The 5 Key Requirements (B1 to B5)

Approved Document B addresses five core statutory requirements:

• B1 (Means of warning and escape): Ensuring occupants can exit safely.
• B2 (Internal fire spread - linings): Regulating material surface flame spread.
• B3 (Internal fire spread - structure): Maintaining compartmentation and fire resistance.
• B4 (External fire spread): Managing fire propagation on building exteriors.
• B5 (Access and facilities for the fire service): Ensuring adequate ingress for responders.

Requirement B1: Designing Safe Means of Escape and Open-Plan Layouts

In open-plan commercial fit-outs, spatial planning must respect escape travel distances. Adding partition walls or acoustic zones can inadvertently turn a clear path into a dead-end or exceed travel limits. Always check your site-specific fire strategy against your floor plans. For further guidance on optimizing space while maintaining safety, refer to our technical overview on commercial fit-out space planning and escape travel distances.

Requirement B2: Specifying Wall & Ceiling Linings, Acoustic Panels, and Decorative Finishes

Requirement B2 limits the fire growth rate on internal surfaces. When specifying acoustic wall panels or decorative finishes, look for Class B-s1, d0 or equivalent ratings. Be aware that many decorative laminates and timber veneers require fire-retardant treatments to meet these standards. If you are also selecting furniture, remember that wall finishes are distinct from fabrics; see our dedicated guide on specifying contract fabrics and upholstery fire standards (BS 5852 / Crib 5) for soft furnishings.

Requirement B3: Fire Doorsets (FD30/FD60), Glazing, and Compartmentation

Fire doors are the most critical component in compartmentation. In most residential fit-outs, FD30 (30-minute fire resistance) is the standard for fire-rated doors. In commercial or high-rise settings, FD60 may be required. Always ensure that ironmongery, such as door closers and intumescent seals, matches the door's certification. For designers working with internal partitions, consider our resource on fire-rated internal glazing systems and acoustic partitions to ensure you don't break the fire seal of a compartment.

Volume 1 vs. Volume 2: Key Distinctions

• Volume 1 (Dwellings): Focuses on single-family homes, flats, and maisonettes. It uses thresholds like 4.5m and 11m to dictate specific escape requirements.
• Volume 2 (Buildings other than dwellings): Applies to offices, retail, and hospitality. It is significantly more stringent regarding travel distances, smoke ventilation, and structural fire protection.

Practical Compliance Checklist

1. Concept: Review the building’s Fire Strategy report to identify protected staircases and escape routes.
2. Development: Check the reaction-to-fire class of all wall and ceiling finishes against B2 requirements.
3. Technical Design: Verify that all door specifications include the required FD rating and correct intumescent hardware.
4. Handover: Obtain certificates of conformity for all fire-rated materials and doorsets to provide to the building owner.