The LWF Blog

Fire Safety for Healthcare Premises – External Fire Spread – Part 50

November 27, 2018 3:14 pm

In LWF’s blog series for healthcare professionals, the aim is to give information on best practice of fire safety in hospitals and other healthcare premises. In part 49 of this series, we began to look at the space separation of buildings to avoid the passage of fire from one building to the next. In part 50, we continue on that subject.

As indicated in the previous blog, where a healthcare building is over 12 metres in height, the maximum percentage of unprotected area should be determined using the BRE guidance set out within BRE Report 187  – External Fire Spread: Building Separation and Boundary Distances

The unprotected area in question should be calculated accurately, however, some small unprotected areas can however be disregarded. For example, the unprotected area of an external wall of a stairway which forms a protected shaft may be disregarded for separation distance purposes, this is due to the stair being a sterile space and posing no real risk. Equally, small unprotected areas of less than 1 metre squared, which may consist of two or more smaller unprotected areas within the square metre area can be left out of the calculation, once more, this is based on risk.

An external surface of combustible material which measures more than 1 mm thick should be considered with the unprotected area calculations, with specific rules relating to these. 

Canopies more than 1 metre from the relevant boundary can be discounted from the provision for space separation.

Obviously, when looking at adequate space separation, the combustibility of the surfaces of external walls must be considered. All surfaces of external walls must provide a surface spread of flame classification of Class 0, with the equivalent European Class of B-s3,d2. It should be noted that national classifications do not exactly relate to the equivalent European classifications and so products available in the UK do not assume a European class unless they have been specifically tested and proved to achieve that standard also.

Where a product classification includes S3,d2 it indicates the lack of a limit set for smoke product or flaming droplets/particles.

Roof coverings too must be considered. All healthcare buildings providing in-patient facilities or undertaking invasive procedures must have roof coverings which comply with Approved Document B – the building regulations in England and Wales (https://www.gov.uk/government/publications/fire-safety-approved-document-b).

In part 51 of this series, LWF will continue discussing space separation issues with junctions of walls and low-level roofs. 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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