The LWF Blog

Fire Engineering Design and Risk Assessment – Compartmentation & Measurement of Fire Resistance – Part 2

August 20, 2018 2:05 pm

In LWF’s Fire Engineering blog series for Architects and others in the building design business, we have been looking at compartmentation. In part 1, the need for fire stopping at compartment boundaries and where services are present was discussed and in part 2, we look at the measurement of fire resistance.


When fire resistance of a compartment is referred to, this means that all elements of a compartment are required to meet a specific minimum period of fire resistance, described in minutes. The requirements for a specific situation will depend on variables such as what the building is to be used for, the height and size of the structure and whether other measures are in place, such as active fire protection.


Approved Document B of the Building Regulations (PDF) includes information which will help determine which period of fire resistance is necessary for a given project.


The term ‘Fire Resistance’ refers to the ability of a building’s construction element to withstand exposure to a standard temperature without loss of fire separation and load-bearing capacity for the referenced amount of time. While such tests are undertaken in a furnace, a real fire situation cannot be directly compared because the rates of heat release and mechanisms of heat transfer differ. A furnace test is more comparable to the post-flashover phase of a fire.


In order to demonstrate fire-resisting performance, products must meet requirements set out in two British Standards – BS  476-21 and BS 476-22.


Alternatively, there is a set of European fire-resistance tests consisting of a classification standard, supported by a number of test standards.


BS EN 13501-2:2016 – Fire classification of construction products and building elements. Classification using data from fire resistance tests, excluding ventilation services


BS EN 1364-1:2015 – Fire resistance tests for non-loadbearing elements. Walls


BS EN 1364-2:2018 – Fire resistance tests for non-loadbearing elements. Ceilings


BS EN 1365-1:2012 – Fire resistance tests for loadbearing elements. Walls


BS EN 1365-2:2014 – Fire resistance tests for loadbearing elements. Floors and roofs


Outside of the UK and Europe, the USA’s National Fire Protection Association produced NFPA 251 -Standard methods of tests of fire resistance of building construction and materials


After testing, the element in question is given a rating in minutes which reflects its ability to fulfil three criteria, as follows:


 Load Bearing Capacity – A measure of how long the element will continue to bear its design load under test conditions


 Integrity – A measure of a separating element’s ability to not develop holes which flame or hot gas could escape through


 Insulation – A measure of the element’s ability to resist heat transmission through a separating element, to limit temperature on the unexposed side. The testing measures if a combustible material in contact with the unexposed side will remain un-ignited.


In part 3 of this series, LWF will continue looking at the measurement of fire resistance of compartment elements. In the meantime, if you have any questions about this blog, or wish to discuss your own project with one of our fire engineers, please contact us.


Lawrence Webster Forrest has been working with their clients for over 25 years to produce innovative and exciting building projects. If you would like further information on how LWF and fire strategies could assist you, please contact Peter Gyere on 020 8668 8663.


While care has been taken to ensure that information contained in LWF’s publications is true and correct at the time of publication, changes in circumstances after the time of publication may impact on the accuracy of this information.


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