The LWF Blog

Fire Engineering Design and Risk Assessment – Compartmentation & Life Safety – Part 6

September 20, 2018 1:04 pm

In LWF’s fire engineering blog series for Architects and others in the building design business, we have recently been looking at compartmentation and life safety. In part 5, we discussed the national building regulations which concern themselves with life safety and compartmentation before moving on to look at the spread of fire. Part 6 continues from that point to talk about how fire spreads before moving on to firefighting.


The rate of flame spread can be roughly calculated by heat transfer equations, which are inversely proportional to the product of the density, thermal conductivity and thermal capacity of the lining. However, for practical purposes, the use of such calculations is impractical as wall linings vary greatly. While commercially available wall linings are available, they are often laminates or composites and therefore may have more complex behaviours than a simple substance when exposed to flame. The surface may de-bond or the layers de-laminate, as well as exhibiting melting and blistering effects.

Other surface types and arrangements can be difficult to predict in a fire situation. One such example is the rapid spread of flames up the wooden escalators at Kings Cross Underground in 1988.

Unless the circumstances are very simple, or easily replicated, it is therefore difficult to make accurate predictions of flame spread and is usually unwise to depend on such calculations.

Fire growth equations can go some way towards providing useful data on fire growth and additional information on the control of flame spread can be found in Approved Document B.

When considering fire dynamics, it’s also worth noting that venting in a compartment can assist with controlling the spread of fire by avoiding or delaying lateral fire spread and in correctly identifying the source of the fire.

Depending upon the type of building, certain facilities may be expected or required by the Fire Service to aid them in carrying out their duties. In high-rise or complex builds, the Fire Service must have good access and water supplies and safe bridgeheads from which to work. The bridgeheads may be linked to firefighting lifts and wet or dry rising water mains.

The provision of bridgeheads saves time and reduces risk to the firefighters involved when they are having to lay hose throughout the building. The vertical compartments, which is what bridgeheads effectively are, should be considered at the design stage as part of the fire engineering strategy for the building.

In part 7 of this series, LWF will look at the issue of property protection. 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.

Share this post