Why Structural Steel Needs Fire Protection
Unprotected structural steel loses strength rapidly when exposed to fire. To preserve load‑bearing capacity and maintain safe evacuation routes, UK projects use tested fire protection systems to achieve specified fire resistance periods (typically 30–120 minutes). The choice of system — intumescent coatings, board encasements or spray‑applied cementitious products — should be driven by verified evidence, buildability and through‑life performance, not just upfront cost.
The 2025 Regulatory Context
Approved Document B (ADB) remains the primary guidance in England. The 2025 amendments withdraw national test classes and strengthen the requirement to provide fire safety information under Regulation 38, reinforcing the need for demonstrable performance and complete handover records. For structural steel protection, the design intent and evidence should be set out clearly in the fire strategy and specifications.
Test & Classification Standards to Know
- EN 13381‑8 — the reference test method for reactive (intumescent) coatings on structural steel; test data supports thickness tables and section‑factor (A/V) ranges.
- EN 13381‑4 — relevant for non‑reactive sprayed systems based on cementitious or gypsum binders.
- UKCA/CE — follow current UK government guidance on product marking and Declarations of Performance for construction products placed on the market.
Always ensure the evidence matches the actual application: profile type (open/closed), orientation, section factor, critical steel temperature, required fire rating and any topcoat or environmental exposure requirements.
System Options: Pros, Cons & Use Cases
Intumescent Coatings (Thin‑Film Reactive)
Suitable for visible steel where architectural finish matters. Factory or on‑site application; delivers low weight and smooth appearance. Requires controlled preparation, DFT measurement and environmental controls during curing. Evidence based on EN 13381‑8 should cover the thickness/section‑factor range and critical temperature assumed by the structural engineer.
Board Encasements
Robust, dry‑trade solution with predictable thickness and easy inspection. Useful around interfaces and where impact resistance or maintenance access is needed. Detailing at joints, fixings and penetrations is critical to maintain continuity at compartment lines.
Spray‑Applied Cementitious
Efficient for complex geometries and hidden steelwork, offering rapid coverage and tolerance to uneven substrates. Requires protection from moisture and damage during programme; specify density, adhesion and finished thickness checks to verify performance.
Five Specification Essentials for 2025 Projects
- State the critical steel temperature used for design checks and select systems with evidence to match.
- Fix the corrosion protection system/primer and confirm compatibility with the intumescent system (where used).
- Define measurable QA: DFT targets and gauges for intumescent, board type/fasteners/centres, spray density/adhesion — with hold points.
- Show continuity at slab edges, connections, service penetrations and where steel crosses compartment lines; coordinate with fire stopping and cavity barriers.
- Handover (Reg 38): provide thickness records, product DoPs/UKCA/CE details, method statements, as‑built drawings and maintenance information for the safety case file.
Quality Assurance on Site
Competency matters. Use third‑party certificated installers (e.g., FIRAS) and adopt a documented inspection and test plan (ITP). For intumescents, confirm surface preparation (Sa/Std), primer compatibility, ambient conditions, wet/DFT readings and cure; for boards, verify fixings and joints; for sprays, verify density/adhesion. Capture photographic evidence and location‑based records to support the building’s golden thread.
Common Failure Modes Found in Surveys
- Unprotected or partially protected members hidden above ceilings or behind services.
- Wrong thickness due to unverified A/V (section factor) or assumed critical temperature.
- Coating applied over incompatible primers or at the wrong environmental conditions.
- Board discontinuities at connections and slab edges; missing seals at penetrations.
- Damaged spray or missing QA evidence, leaving performance unproven.
How Steel Protection Integrates with the Wider Fire Strategy
Steel protection is one part of a coordinated passive fire protection strategy. It must align with compartmentation, fire‑resisting linings, and the detailing of junctions and services. Early coordination prevents clashes and ensures that protection is continuous where it matters most — at escape routes and structural nodes.
How We Help
We provide end‑to‑end support for structural steel fire protection — from design input and product selection to competent installation and full handover documentation. Our teams work across intumescent, boards and sprays, integrating with fire stopping, cavity barriers and compartment surveys to deliver compliant, durable outcomes.
Firesafe Installations Ltd — protecting lives, property and businesses.
📞 Call us on 0151 546 1069
📧 Email info@firesafe-installations.co.uk
🌐 Or use our contact form to request a specification review or survey.
