Fire resistance classes

The fire resistance of building components and constructions are classified in different fire resistance classes or combinations of those. The different fire resistance classes specify different performance criteria.

Normally the fire resistance classification is followed by as a time limit in minutes 15, 30, 45, 60, 90, 120, 180, 240, or 360 which shows the time the performance criteria is fulfilled during a standardized fire test.

Requirements for the classes

R                   Load bearing capacity

E                   Integrity

I                    Insulation

W                  Radiation

M                  Mechanical resistance

C                   Self closure

S                   Smoke leakage

K                   Fire protection (coverings)

R                   Load bearing capacity

The load bearing capacity, R, is the ability for a building element to resist a fire when exposed on one or several sides and when supporting an external load during a time period without losing its stability. The performance criteria varies on the type of construction. The two following things are distinguish between:

Elements that are loaded in bending (for example floor structures and beams or compression in walls) where the requirements are the rate of deformation and maximum deformation.

Elements that are axial loaded (for example columns and walls) where the requirements are the rate of deformation and maximum deformation.

E                    Integrity

The integrity E is the ability of a test specimen of a separating element of building construction, when exposed to fire on one side, to prevent the passage through it of flames and hot gases and to prevent the occurrence of flames on the unexposed side. The requirements are the following:

 - cracks gaps of certain dimenisons

- ignition of a cotton wool pad

- sustained flaming on the unexposed side

I                     Insulation

The insulation is the ability of a test specimen of a separating element of building construction when exposed to fire on one side, to restrict the temperature rise of the unexposed face to below specified levels.

W                  Radiation

The radiation W is the ability of the element of construction to withstand fire exposure on one side only, so as to reduce the probability of the transmission of fire as a result of significant radiated heat either through the element or from its unexposed surface to adjacent materials. The element may also need to protect people in the vicinity.

M                  Mechanical action

The mechanical action M is the ability of the element to withstand impact, representing the case where structural failure of another component in a fire causes an impact on the element concerned. The test is carried out immediately after the building element has been tested during a certain time for another classification (R, E or/and I).

C                   Self closing

The self closing C is the ability of an open door or window to close fully into its frame and engage any latching device that may be fitted, without human intervention, by stored energy, or by mains power backed up by stored energy in case of power failure.

S                    Smoke leakage

The smoke leakage S is the ability of an element of construction to reduce the passage of hot and/or cold gases or smoke from one side of the element to the other to below specified levels.

K                   Fire protection ability (coverings)

The fire protection ability K is the ability of a wall or ceiling covering to provide for the material behind the covering protection against ignition, charring and other damage for a specified period of time. Coverings are the outermost parts of building elements, such as walls, floors and roofs.

Related Information

Technical Areas

Fire Research

Contact Persons

Lars Boström

Phone: +46 10 516 56 08

SP Technical Research Institute of Sweden, Box 857, SE-501 15 Borås Phone +46 10-516 50 00, E-mail info@sp.se