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Fire Safety for Facilities Management Personnel – Structural Fire Protection – Part 149

May 16, 2022 11:08 am

Lawrence Webster Forrest (LWF) is a specialist fire engineering and fire risk management consultancy whose aim is to give information on best practice in fire safety for facilities management personnel through this blog series. In part 148, LWF looked at how the requirement within the building regulations, that a building should be constructed to maintain stability for a reasonable period in the event of a fire, translates into structural engineering practicalities. In part 149, we consider how a building’s construction can help to protect against the spread of fire and smoke.

A building is constructed with various sub-divisions of walls and floors which known as compartments and these are used to limit the spread of fire and smoke from one compartment to the next. The idea is that if a fire starts in a compartment within the building, it is contained in that area for a sufficient amount of time for the Fire Service to attend the fire. A compartment is not necessarily the same as a room.

In England and Wales, the performance requirements for compartments are laid out in B3 of Schedule 1 of the Building Regulations 2000 and states:

 (3) Where reasonably necessary to inhibit the spread of fire within the building, measures shall be taken, to an extent appropriate to the size and intended use of the building, comprising either or both of the following—

(a) sub-division of the building with fire-resisting construction;

(b) installation of suitable automatic fire suppression systems.

In Approved Document B, the fire-resisting walls and floors are referred to as compartment walls and floors. It specifies maximum compartment sizes for differing purpose groups by stating maximum floor areas, or for multi-storey storage buildings, in terms of volume.

The permitted maximum compartment size can be effectively doubled if sprinkler systems are in place. A single-storey warehouse is not compartment-size-limited if sprinklers are provided. However, if an industrial or storage building is over 18 metres in height, the maximum compartment size is greatly reduced.

While maximum compartment sizes are stated for most purpose groups, there are some which are not – offices, car parks for light vehicles and some single-storey buildings. There are various reasons why this is the case, but it mostly relates to fuel load and occupancy type.

In part 150 of this series, LWF will look at why sprinkler systems were added to the building regulations in 2000. In the meantime, if you have any queries about your own facilities or wish to discuss this blog series, please contact LWF on freephone 0800 410 1130.


Lawrence Webster Forrest is a fire engineering consultancy based in Surrey with over 25 years’ experience, which provides a wide range of consultancy services to professionals involved in the design, development and construction and operation of buildings.

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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