Fire protection of structures

Solutions & Applications · Fire Protection & Insulation

Stone wool is ‘born of fire’ — produced by melting rock at approximately 1,520 °C — and is therefore non-combustible. However, this does not make the building fire-rated. Fire protection has two distinct aspects, and confusion between them is the cause of most errors in the design.

The two sizes

	Reaction to fire	Fire resistance
Standard	EN 13501-1	EN 13501-2
What matters	How much does a material contribute to a fire?	How long does a structural element continue to function?
Applies to	The material	The system — wall, ceiling, door
Classification	A1, A2, B, C, D, E, F	R, E, I — e.g. EI 30 / EI 60 / EI 90 / EI 120
Example	Stone wool: A1	Partition wall with stone wool and fire-rated plasterboard: EI 90

The letters denoting resistance are defined as follows: R is the load-bearing capacity, E is integrity — the element does not allow the passage of flame or hot gases — and I is thermal insulation performance, meaning that the unexposed side does not reach a dangerously high temperature. An EI 90 partition maintains both properties for ninety minutes.

The classification of the material, letter by letter

Classification	What does this mean?	Standard materials
A1	Non-combustible — makes no contribution to a fire	Stone wool, mineral wool, cement board, FIREBOARD fire-resistant board
A2	Practically non-combustible, with very low organic content	Plasterboard, wood wool with a mineral binder
B to E	Increasing contribution to the fire	Foam insulation — XPS is classified as E

The following indicators are equally important and are often overlooked:

• s1, s2, s3 — smoke production. In building fires, smoke kills before the flame does: it reduces visibility in escape routes to zero and hinders rescue operations. s1 represents the lowest level of smoke production.
• d0, d1, d2 — flaming droplets. d0 means none. Drips carry the fire downwards and ignite secondary fires — which is why they are particularly important in garage ceilings and on façades.

An A2-s1,d0 is therefore practically non-combustible, with minimal smoke and no droplets — and is not to be confused with A1, which contains no organic material whatsoever.

Protection of the load-bearing structure

It is the argument that does not concern people’s lives but the cost of restoration — and often determines the decision.

As early as ~270 °C, the bond between concrete and steel begins to deteriorate and cracks appear. As the temperature rises, the moisture within the concrete turns to steam; the pressure cannot be released quickly enough and the surface flakes off in sheets, exposing the reinforcement. The exposed steel rapidly loses its strength.

A layer of non-combustible material between the fire and the load-bearing element delays the transfer of heat. It does not protect the contents — it protects the structural integrity, and in doing so prevents the need for repairs using epoxy resins and carbon fibres, which cost many times more than the original insulation. On metal structures, the cladding is made of A1-grade fireboard.

The most common way for a fire-rated element to be invalidated

It’s not the material. It’s the penetrations. An EI 120 partition with an unsealed cable penetration is not EI 120 — it’s a partition with a hole in it.

Point	The right solution
Cable and pipework penetrations	Certified fire barrier systems, of the same class as the partition — standard foam is not a fire barrier
Ventilation ducts	Fire barriers at penetration points — insulation around the air duct is not sufficient
Connection to the slab	Top-end sealing that allows the slab to move without creating a gap
Switch boxes	Do not place them back-to-back within the same opening
Access hatches	Of the same class as the wall, e.g. F-TEC F90
Grouting	Complete filling of joints — an open joint acts as a passage for hot gases

The rule is simple: the fire resistance of a component is equal to that of its weakest point.

Where it is used

Position	Solution	What else it offers
Fire-rated dry construction partitions	Stone wool core + fire-rated plasterboard on a metal frame	Sound insulation and thermal insulation in the same thickness
Lining of metal structures, shafts and high-risk areas	FIREBOARD A1 fire-resistant board	Non-combustible surface, not just fire resistance
Garage and entrance hall ceilings	Wood-woolle or composite board with a stone wool core	Sound absorption and visible natural surface
External wall insulation with foam insulation	Fire barriers with stone wool strips	—
External wall insulation made entirely of stone wool	Non-combustible system across the entire façade	Fire barriers are being removed — one detail instead of many

What the regulations require

Under the current fire safety regulations (Presidential Decree 41/2018), non-combustible insulation materials in cladding are required in buildings adjacent to boundaries or to another building, school premises, hospitals, venues accommodating more than 1,000 people and high-rise buildings over 23 m. From 2023, this requirement will be extended, under the Fire Protection Regulations for Properties, to include properties situated within or near woodland areas.

In practice, this requirement is the first to be checked in a thermal insulation design: if it is present, it determines the material, and everything else — thickness, render, colour — follows.

All three sizes together

Stone wool is not chosen solely for fire resistance. At the same thickness, it provides thermal insulation with λ ≈ 0.035 W/mK, vapour permeability with μ ≈ 1 — practically the same resistance as still air — and sound absorption, thanks to its open-fibre structure which converts sound energy into friction. It is one of the few materials where regulatory requirements and user benefits coincide.

Stone wool & mineral wool

Fire-rated Partitions & Cladding

Ceilings, Cladding & Wet Areas

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