UK Fire Protection Guidance for Structural Steel: What Building Owners Should Know

Fire protection for structural steel is not selected from a single rule or a universal coating thickness. The correct approach is project-specific and starts with the building design, fire strategy and the documents issued by the responsible project team.

What Approved Document B does

In England, Approved Document B provides statutory guidance supporting the fire-safety requirements of the Building Regulations. It covers matters including means of escape, internal and external fire spread, access for the fire service and structural fire resistance.

Approved Document B is guidance rather than a coating specification. The required performance for a particular element depends on factors such as the building use, height, compartmentation, basement arrangement and the role of that element in the structure. Projects in Wales, Scotland and Northern Ireland must be checked against the guidance and regulatory system that applies there.

The fire engineer, designer or other responsible project professional should establish the required performance. A coating contractor should not guess it from the building type alone.

Information needed for structural steel

Before an intumescent coating system can be confirmed, the project team will normally need to establish:

• The required fire-resistance period for each relevant element or zone
• The steel member sizes and the sides exposed to fire
• The design or limiting temperature used by the structural design
• The section factor for each steel member
• The tested coating system and its approved loading tables
• The existing or proposed primer and any decorative topcoat
• The environmental exposure and whether the steel is internal, semi-exposed or external
• The inspection, measurement and handover records required by the contract

The specification should identify who is responsible for each input. Where information is missing, it should be resolved by the project designer, fire engineer, structural engineer or coating manufacturer before application begins.

Why coating thickness is project-specific

The amount of protection required is influenced by the fire-resistance period, the section factor, the steel design temperature and the performance evidence for the selected product. Two steel members on the same project may therefore require different coating builds.

SteelConstruction.info's structural steel fire-protection guidance explains how section geometry, exposure and the selected protection system affect the design. The final dry film thickness should come from the approved specification and the coating manufacturer's data for the selected tested system.

Product compatibility and exposure

An intumescent coating forms part of a complete system. The primer, intumescent layer and any topcoat need to be compatible with one another. The selected system must also be suitable for the intended exposure and service conditions.

Existing primer should not be assumed to be compatible simply because it appears sound. Its identity and condition need to be established, and the intumescent manufacturer should confirm compatibility where required.

Inspection and project records

The project documents should define the inspection plan, acceptance criteria and records needed at handover. Depending on the specification, these may include substrate checks, environmental readings, batch details, wet and dry film measurements, photographs, location records and independent inspection.

Records demonstrate what was applied; they do not replace the design, tested-system evidence or approvals required for the project.

Planning the application work

Newlook Protective Coatings provides on-site preparation and intumescent coating application for structural steel projects. Before confirming the application scope, the team will need the relevant project specification, steel information, selected coating system and site requirements.

Newlook does not replace the fire engineer, structural engineer, building-control process or coating manufacturer. Performance requirements and system selection must be supplied or approved by the responsible project team.

For further technical guidance, consult the current Approved Document B collection and the Association for Specialist Fire Protection technical documents.

To discuss the preparation and application requirements for a defined project, see Newlook's Intumescent Coatings service.