Fire risk classification

The four classes

The Hungarian fire regulation uses four risk classes, in increasing order: very low, low, moderate and high risk.

Classification is not about the “quality” of the building but about how much damage and how much human risk a fire could cause.

What the classification is based on

The regulation takes several aspects into account, typically:

• the use (residential, office, education, healthcare, industrial, storage…),
• the number of storeys and the height of the highest occupied level,
• the number of occupants,
• the occupants’ ability to escape — are they asleep, do they know the building, can they escape unaided,
• the fire load, that is, how much combustible material is present.

Classification is done per fire compartment, and a building may contain several risk classes; for structural requirements the governing class counts.

Why this is the first step

Because the fire resistance requirement for the structures follows from it. The same wall gets a different requirement in a single-storey house and in a multi-storey building used by many people.

A single-dwelling, low building typically falls into the lower risk classes, where the fire resistance period required of structures is in the smaller range. In a higher risk class this increases, and further requirements enter — compartmentation, detection or suppression systems, stricter materials.

The exact values are given in the tables of the regulation’s annexes; these should not be estimated but read from the text in force.

Why it matters to know this early

The risk class feeds back into the structure and the build-up: it decides what fire resistance has to be verified, how many lining layers are needed, and whether there is a restriction on the insulation material. If this emerges at the end of design, the build-up has to be reworked — which affects everything from wall thickness to price.

So settle the classification at concept stage, before the build-up is fixed.

The methodology

There is a separate fire safety technical guideline for the classification method. Applying it is voluntary but gives the presumption of compliance. The legal status of the guidelines.

The point

“What fire resistance does the wall need?” has no answer without the classification. The risk class is the gate through which every other fire requirement passes.