Untitled Document

PROTECTED ZONES

Where buildings are divided into 2 or more fire compartments, the purpose of the separating compartment wall is to ensure that the spread of fire from one compartment to another is prevented. Note that partition walls are not compartment walls but are used to create rooms within a fire compartment. The external enclosure of a building will play a key role in ensuring that fire spread around or over the compartment wall is inhibited. The specification for the fire performance of external walls and roofs must ensure that they do not permit the spread of fire around or over any compartment wall within the building. The LPC Design Guide for the fire protection of buildings introduces this concept as the 'Protected Zone' which is defined as 'the sections of roof, external walls and supporting frame adjacent to and within a specified distance on each side of a compartment wall'. Designers should be aware that the external walls, roofs and supporting frame in the protected zone may well require a higher fire resistance than walls and roofs elsewhere in the building, depending on the findings of the risk assessment.

Extent of Protected Zone
The protected zone along the external wall is the distance between compartment wall and the next structural member on each side of the compartment wall. This may need to be further extended if fire exposure from an adjacent building is likely to compromise the compartmentation. If the next structural member is within 1 metre of the compartment wall, the protected zone should be extended to the next structural member. In addition, if part of the wall is less than 1 metre from the relevant boundary, as defined in Approved Document B - Fire Safety, supporting Building Regulations, higher fire resistance levels will be required.

It is important that external walls, roofs and supporting framework in the protected zone are provided with adequate fire resistance or alternative protection to prevent the early spread of fire from one side to the other.
-	For compartment walls parallel to the line of the roof ridge, the protected zone depends on the risk assessment for the business, but is often not less than 5 metres.
	Note that whilst risk assessments arising from the Fire Precautions (Workplace) Regulations 1997 are intended to protect people in buildings, the risk assessment for the insurer will need to include both risk to people and the business which is housed in the building, including any business interruption which may arise.
-	For compartment walls at right angles to the line of the roof ridge, the protected zone should extend to the next structural member beyond 1 metre from the wall.

Fire Resistance Requirements
The requirements for protected zones will vary according to the use of the building, the risk assessment and the associated business risk. While actual requirements should be confirmed at the earliest opportunity with the insurer, additional requirements can be found in Loss Prevention Standard LPS 1181: Part 1, Appendix B.

The figures indicated below are those appearing in the draft document August 2002.

External Grade

Integrity
[minutes]

Insulation
[minutes]

Typical application, see Table 2.2 of LPC Design Guide

EXT -A60

60

60*

Retail warehouse 4b, superstore, industrial 6b, and storage 7a

EXT -A30

30

30*

Shop 4a, commercial, industrial 6a

EXT - A15

30

15

Fully sprinklered buildings

* Roof and external wall cladding systems which achieve an insulation time within 90% of this figure may be deemed to satisfy the requirements.

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