The LWF Blog

Fire Safety Engineering for Design – Building Types & Fire Precautions – Part 22

March 29, 2021 12:10 pm

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 21, LWF discussed situations where buildings have a large floor area before considering the effect of building volume on fire safety. In part 22, we look at a building’s proximity to the site boundary and to adjacent buildings.

Where a building is situated close to the site boundary, or is in close proximity to another building, there is an increased risk of fire spreading from one building to the next. Mitigating the increased level of risk can be approached through increased controls on compartmentation within the building, restricting the materials used on the façade to those which are non-combustible and fire-resisting, and ensuring there is adequate firefighting access through firefighting shafts, rather than relying on perimeter access.

The Building Regulations for England and Wales and equivalent regulation for Scotland and Northern Ireland require the external walls of a building to resist fire spread over the walls and from one building to another. Approved Document B lays out the proportion of unprotected areas of the façade permitted and this is determined by the building’s proximity to the boundary and is also affected by the type of occupancy based on potential fire load.

It should be noted that where the occupancies of the buildings under consideration involve a high life risk, Approved Document B also determines that fire resistant materials are to be used between buildings on the same site and between certain uses in a single building.

The use of compartmentation in buildings means that when a fire starts, it is kept in that area for a given amount of time and prevented from spreading to other compartments. In most cases, this time is sufficient for a safe evacuation of the affected buildings or areas and for the Fire Service to attend the fire. The effect of compartmentation in a building in close proximity to the boundary or to another building is that it restricts the area of radiation at the boundary of the building.

Where this method conflicts with building occupancy, sprinkler protection can be used to control the fire and restrict fire size. Another benefit is that sprinkler use means more accurate calculations can be made of potential fire size and the benefit to the boundary condition can be anticipated.

In part 23 of LWF’s series on fire engineering, we will begin to discuss fire load. 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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