Fire performance is often the most scrutinized specification in international sandwich panel procurement. Different markets enforce different standards — European EN 13501-1, Chinese GB 8624, American ASTM E84 — and the core material largely determines the achievable fire rating. This guide explains the common fire classifications for sandwich panels and how they map to material choices.
Fire Rating Classifications for Sandwich Panels
The European EN 13501-1 classification system is the most widely referenced in international trade. It rates materials from A1 (non-combustible) to F (easily flammable):
| Euroclass | Meaning | Core Material | Typical Application |
|---|---|---|---|
| A1 | Non-combustible — no contribution to fire | Rock wool (mineral fiber) | Fire-rated walls, public buildings, high-rise facades |
| A2 | Limited combustibility — negligible contribution | High-density rock wool, specialty PIR | Commercial buildings, mixed-use developments |
| B1 | Flame-retardant — difficult to ignite | PIR, fire-retardant PU, treated EPS | Industrial buildings, warehouses, cold rooms |
| B2 | Normal combustibility | Standard PU, standard EPS | Agricultural buildings, temporary structures |
Rock Wool — A1 Non-Combustible
Rock wool (mineral wool) is the only common sandwich panel core capable of achieving A1 classification. It is made from molten rock spun into fibers, making it inherently non-combustible.
Rock wool panels are specified where fire separation is required by code or where insurance underwriters mandate non-combustible materials:
- Fire-rated internal separation walls
- Building envelopes in high-rise or public-access structures
- High-temperature processing areas (foundries, kilns, boiler rooms)
- Projects requiring third-party fire engineering sign-off
Trade-off: Rock wool has higher thermal conductivity (~0.045 W/m·K) than PU or PIR, so insulation thickness may need to increase. It is also heavier, which affects roof-span calculations and purlin spacing.
PIR — The B1 Workhorse with A2 Potential
PIR (polyisocyanurate) is the upgraded version of polyurethane with modified chemistry that improves fire behavior. Standard PIR panels achieve B1 classification, and some high-density formulations can reach A2-s1,d0 under EN 13501-1.
PIR is the most common choice when projects need a balance of fire performance, thermal insulation, and cost:
- Cold storage and freezer facilities where both fire rating and thermal performance matter
- Food processing plants with hygiene and fire requirements
- Industrial buildings in markets with B1 minimum requirements
PU — B1 or B2 Depending on Formulation
Standard polyurethane panels typically achieve B2 classification. With fire-retardant additives in the foam formulation, PU can reach B1. The key distinction is that PU does not char and form a protective layer the way PIR does, so its fire behavior is less predictable in sustained exposure.
PU panels are widely used for industrial roofs and walls where the local code permits B2 or B1 materials and the priority is thermal insulation at a competitive cost.
EPS — Budget Option with Fire Retardant Variants
EPS (expanded polystyrene) is inherently combustible. Standard EPS panels are B2 or lower. With brominated fire retardants added during the EPS bead expansion process, the panel can achieve B1 classification — but the fire-retardant properties may degrade over time with UV and moisture exposure.
EPS is appropriate for:
- Agricultural buildings and poultry farms
- Low-budget temporary warehouses
- Markets without strict fire-code enforcement
Steel Facing and Fire Performance
The steel facing sheets also contribute to fire performance. Thicker steel (0.50 mm or above) provides better structural integrity during fire exposure, delaying panel collapse. PVDF and HDP coatings add negligible combustible mass.
How to Specify Fire Rating in an International Enquiry
When requesting a fire-rated panel quotation, include:
- Target fire classification: State the required Euroclass or local equivalent (A1, A2, B1)
- Reference standard: EN 13501-1, GB 8624, ASTM E84, BS 476, or local building code
- Application context: Wall, roof, ceiling, or fire-separation element
- Building type: Industrial, commercial, public, or residential — different codes apply
Project Example: Fire-Rated Roof Panels for Indonesia
In a recent Indonesian factory project, the buyer needed A-grade fire performance for a large industrial roof. LIAOHE supplied PU-edge rock wool roof panels that combined the fire rating of a mineral-wool core with the installation advantages of a PU edge seal. The hybrid specification met local fire-code requirements while keeping the panel weight and joint geometry suitable for efficient site installation.
Get Fire-Rating Documentation
LIAOHE provides fire-rating test reports, material certifications, and compliance documentation according to the destination market’s requirements.
Request fire-rated panel specification and certification →
FAQ
What is the difference between B1 and A2 fire rating?
B1 is flame-retardant — the material is difficult to ignite and self-extinguishes. A2 has limited combustibility, meaning it contributes negligibly to a fire. A2 is a higher standard and usually requires rock wool or specialty PIR cores.
Can PU panels achieve A2 fire rating?
Standard PU cannot achieve A2. PIR can reach A2 with specific high-density formulations, and rock wool is the most reliable material for A1 or A2 requirements.
Which fire rating do I need for an industrial warehouse?
It depends on local building codes, insurance requirements, and the warehouse contents. Many industrial warehouses are built with B1-rated panels, but facilities storing flammable goods, high-bay warehouses, or buildings in fire-sensitive zones may require A2 or A1.
Does thicker steel facing improve fire rating?
Thicker steel (0.50 mm+) improves structural integrity during fire exposure but does not change the panel’s Euroclass. The core material determines the classification; the steel affects how long the panel maintains load-bearing capacity.