The LWF Blog

Fire Safety Engineering for Design – Building Types & Fire Precautions – Part 21

March 22, 2021 10:50 am

LWF’s Fire Safety Engineering blog series is written for Architects, building designers and others in the construction industry to highlight and promote discussion on all topics around fire engineering. In part 20, LWF looked at how an increased building area impacts fire engineering design. In part 21, we continue discussing buildings with a large floor area before considering the effect of building volume.

Guidance documents for fire safety and fire engineering often view a building with a large floor area in the same way – they assume a fire will be a fully-involved compartment fire that has a uniform temperature generation and limited ventilation. In real terms, a fire in a large floor area building is likely to be localised and could have almost unlimited ventilation. Such fires are likely to move along the floor plate and maintain a mainly stable fire load consumption. A ‘travelling’ fire, such as this, can produce different heating regimes to the standard time-temperature model and can ultimately cause non-standard structural responses.

Consideration of the type of fire that may occur in a given space/compartment/building and the resulting properties of that fire type should be at the forefront when undertaking structural fire engineering assessments.

A large building volume can have a significant effect on the type and behaviour of a fire. Where sufficient fire load is present, a large compartment can result in larger fires. In cases where there are extended and uncompartmented areas, such as warehousing, this can create an environment where fire development and spread could increase and grow to the point of absolute loss. In such cases, the importance of early detection is paramount and the addition of smoke venting, oxygen depletion and water suppression methods can help to ensure fires are controlled.

It should be noted, however, that an increased building volume does not automatically equal increased fire load or risk. An increased volume can also have a positive result for evacuation and escape times, as the smoke will rise leaving a clear layer of breathable air for the building occupants as they leave the building.

Means of escape and firefighting implications can be very different in a large volume building. This is related to the timing of evacuation egress in relation to the entry of firefighters. An increased risk to escape is sometimes considered also an increased risk to firefighters, but this is not necessarily the case in a large volume building.

Some large volume buildings do not have commensurate fire load, e.g. mall halls or transport terminals and lower standards of fire resistance could be considered acceptable when coupled with fire containment and smoke control systems.

In part 22 of LWF’s series on fire engineering, we will look at a building’s proximity to site boundary and adjacent buildings. 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 the LWF office on 0800 410 1130.

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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