# The LWF Blog

## Fire Safety for Healthcare Premises – External Fire Spread – Part 49

November 22, 2018 11:16 am

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 48 of this series, we began to look at the potential for external fire spread and how the construction of the building(s) should take into account the possibility of fire spread from one area of a building to another or from one building to another. In part 49, we continue from that point by looking at space separation.

In healthcare buildings which are up to 12 metres in height, there is a maximum percentage of unprotected area of an external wall and this is in relation to the distance to adjacent compartments, buildings or boundaries, as follows:

2.5 metres distance between face of building and relevant boundary – 20% unprotected area

5 metres distance between face of building and relevant boundary – 40% unprotected area

7.5 metres distance between face of building and relevant boundary – 60% unprotected area

10 metres distance between face of building and relevant boundary – 80% unprotected area

12.5 metres + distance between face of building and relevant boundary – 100% unprotected area

For an exact calculation, the basis above can be plotted onto a simple line graph.

For a boundary in this instance to be considered ‘relevant’, it should coincide with or be parallel to or be at an angle of not more than 80 degrees to the side of the building. Where a new building is to be placed in conjunction to an existing building, there becomes a need for a notional boundary. In the case of establishing a notional boundary, this should be set in the area between the two buildings as per these rules:

It must be assumed to exist in the space between two buildings so that one of the buildings would comply with the provisions for space separation having regard to the amount of its unprotected area. In practice, if one of the buildings is existing, the position of the boundary will be set by the space separation factors for that building.

The siting of the new building or the second building, if both buildings are to be new, can be checked to see that it also complies using the notional boundary as the relevant boundary for the second building.

The issue of notional boundaries is further examined in Approved Document B section 13.6.

Where a healthcare building is over 12 metres in height, the maximum percentage of unprotected area should be determined from the methods set out in the BRE Report 187 – External Fire Spread: Building Separation and Boundary Distances.