Section 8: Compartmentation/ sprinklers

Provision of compartmentation

All purpose groups

8.1 All of the following should be provided as compartment walls and compartment floors and should have, as a minimum, the fire resistance given in Appendix B, Table B3.

8.2 A wall common to two or more buildings should be a compartment wall.

8.3 Parts of a building occupied mainly for different purposes should be separated from one another by compartment walls and/or compartment floors. Compartmentation is not needed if one of the different purposes is ancillary to the other. See paragraphs 0.23 and 0.24.

8.4 Effective compartmentation relies on both of the following.

a. Fire resistance should be continuous at the join between elements forming a compartment.

b. Any openings between two compartments should not reduce the fire resistance.

8.5 The lowest floor in a building does not need to be a compartment floor.

Protected shafts

8.6 Stairs and service shafts connecting compartments should be protected to restrict the spread of fire between the compartments. These are called protected shafts. Walls or floors surrounding a protected shaft are considered to be compartment walls or compartment floors.

Places of special fire hazard

8.7 Fire resisting construction enclosing these places should achieve minimum REI 30. These walls and floors are not compartment walls and compartment floors.

‘Residential (institutional)’ buildings including health care

8.8 All floors should be constructed as compartment floors.

8.9 Paragraphs 2.35 and 2.36 give guidance on the provisions for compartment walls in care homes that use progressive horizontal evacuation.

‘Residential (other)’ buildings

8.10 In ‘residential (other)’ (purpose group (2(b)) buildings, all floors should be compartment floors.

Non residential buildings

8.11 In buildings in a non-residential purpose group (purpose groups 3 to 7), the following should be compartment walls and compartment floors.

a. Every wall needed to divide the building to observe the compartment size limits in Table 8.1 (Diagram 8.1a).

b. Every floor, if the building or separated part of the building (see paragraph 8.19) has a top storey that is more than 30m above ground level (Diagram 8.1b).

c. The floor of the ground storey, if the building has one or more basements (Diagram 8.1c), except in small premises (see paragraph 4.2).

d. The floor of every basement storey (except the lowest floor), if the building or separated part has a basement more than 10m below ground level (Diagram 8.1d).

e. If the building comprises ‘shop and commercial’, ‘industrial’ or ‘storage’ premises (purpose groups 4, 6, 7): every wall or floor dividing a building into separate occupancies (spaces used by different organisations, whether they fall within the same purpose group or not).

f. See also the provision in paragraph 5.46 for store rooms in shops to be separated from retail areas by fire resisting construction (minimum REI 30).

8.12 In two storey ‘shop and commercial’ or ‘industrial’ buildings (purpose groups 4 or 6), where the use of the upper storey is ancillary to the use of the ground storey, the ground storey may be treated as a single storey building for fire compartmentation purposes where all of the following apply.

a. The area of the upper storey does not exceed the lower of:

i. 20% of the area of the ground storey

ii. 500m2.

b. The upper storey is compartmented from the lower one.

c. The upper storey has a means of escape independent of the lower storey escape routes.
Every place of special fire hazard (see Appendix E) should be enclosed with fire resisting construction.

Buildings containing one or more atria

8.13 Detailed advice on atria in buildings is given in Annexes B and C of BS 9999. For the purposes of this document, BS 9999 applies only where the atrium breaches a compartment.

Sprinklers

8.14 Buildings within the ‘office’, ‘shop and commercial’, ‘assembly and recreation’, ‘industrial’ and ‘storage and other non-residential’ (except car parks for light vehicles) purpose groups (purpose groups 3 to 7(a)) require sprinklers where there is a top storey above 30m. The sprinkler system should be provided in accordance with Appendix E.

Construction of compartment walls and compartment floors

General provisions

8.15 All compartment walls and compartment floors should achieve both of the following.

a. Form a complete barrier to fire between the compartments they separate.

b. Have the appropriate fire resistance, as given in Appendix B, Tables B3 and B4.

8.16 Timber beams, joists, purlins and rafters may be built into or carried through a masonry or concrete compartment wall if the openings for them are both of the following.

a. As small as practicable.

b. Fire-stopped.

If trussed rafters bridge the wall, failure of the truss due to a fire in one compartment should not cause failure of the truss in another compartment.

8.17 Where services could provide a source of ignition, the risk of fire developing and spreading into adjacent compartments should be controlled.

Compartment walls between buildings

8.18 Adjoining buildings should only be separated by walls, not floors. Compartment walls common to two or more buildings should comply with both of the following.

a. Run the full height of the building in a continuous vertical plane.

b. Be continued through any roof space to the underside of the roof.

Separated parts of buildings

8.19 Compartment walls forming a separated part of a building should run the full height of the building in a continuous vertical plane.

Separated parts can be assessed independently to determine the appropriate standard of fire resistance in each. The two separated parts can have different standards of fire resistance.

Other compartment walls

8.20 Compartment walls not described in paragraphs 8.18 and 8.19 should run the full height of the storey in which they are situated.

8.21 Compartment walls in a top storey beneath a roof should be continued through the roof space.

Junction of compartment wall or compartment floor with other walls

8.22 At the junction with another compartment wall or an external wall, the fire resistance of the compartmentation should be maintained. Fire-stopping that meets the provisions in paragraphs 10.24 to 10.29 should be provided.

8.23 At the junction of a compartment floor and an external wall with no fire resistance, the external wall should be restrained at floor level. The restraint should reduce movement of the wall away from the floor if exposed to fire.

8.24 Compartment walls should be able to accommodate deflection of the floor, when exposed to fire, by either of the following means.

a. Between the wall and floor, provide a head detail that is capable of maintaining its integrity while deforming.

b. Design the wall so it maintains its integrity by resisting the additional vertical load from the floor above.

Where compartment walls are located within the middle half of a floor between vertical supports, the deflection may be assumed to be 40mm unless a smaller value can be justified by assessment. Outside this area, the limit can be reduced linearly to zero at the supports.

For steel beams that do not have the required fire resistance, reference should be made to SCI Publication P288.

Junction of compartment wall with roof

8.25 A compartment wall should achieve both of the following.

a. Meet the underside of the roof covering or deck, with fire-stopping to maintain the continuity of fire resistance.

b. Be continued across any eaves.

8.26 To reduce the risk of fire spreading over the roof from one compartment to another, a 1500mm wide zone of the roof, either side of the wall, should have a covering classified as BROOF(t4), on a substrate or deck of a material rated class A2-s3, d2 or better, as set out in Diagram 8.2a.

Thermoplastic rooflights that, because of paragraph 14.7, are regarded as having a BROOF(t4) classification are not suitable for use in that zone.

8.27 Materials achieving class B-s3, d2 or worse used as a substrate to the roof covering and any timber tiling battens, fully bedded in mortar or other suitable material for the width of the wall (Diagram 8.2b), may extend over the compartment wall in buildings that are both of the following.

a. A maximum of 15m high.

b. In one of the following purpose groups.

i. All residential purpose groups (purpose groups 1 and 2) other than ‘residential (institutional)’ (purpose group 2(a)).

ii. ‘Office’ (purpose group 3).

iii. ‘Assembly and recreation’ (purpose group 5).

8.28 Double-skinned insulated roof sheeting should incorporate a band of material rated class A2-s3, d2 or better, a minimum of 300mm in width, centred over the wall.

8.29 As an alternative to the provisions of paragraph 8.26 or 8.27, the compartment wall may extend through the roof for a minimum of either of the following (see Diagram 8.2c).

a. Where the height difference between the two roofs is less than 375mm, 375mm above the top surface of the adjoining roof covering.

b. 200mm above the top surface of the adjoining roof covering where either of the following applies.

i. The height difference between the two roofs is 375mm or more.

ii. The roof coverings either side of the wall are of a material classified as BROOF(t4).

Openings in compartmentation

Openings in compartment walls separating buildings or occupancies

8.30 Openings in a compartment wall common to two or more buildings, or between different occupancies in the same building, should be limited to those for either of the following.

a. A fire doorset providing a means of escape, which has the same fire resistance as the wall and is fitted in accordance with the provisions in Appendix C.

b. The passage of a pipe that complies with the provisions in Section 10.

Openings in other compartment walls or in compartment floors

8.31 Openings should be limited to those for any of the following.

a. Fire doorsets fitted in accordance with the provisions in Appendix C.

b. Pipes, ventilation ducts, service cables, chimneys, appliance ventilation ducts or ducts encasing one or more flue pipes, complying with the provisions in Section 10.

c. Refuse chutes of class A1 construction.

d. Atria designed in accordance with Annexes B and C of BS 9999.

e. Protected shafts that conform to the provisions in the following paragraphs.

Protected shafts

8.32 Any stair or other shaft passing directly from one compartment to another should be enclosed in a protected shaft. Protected shafts should be used for the following only, but may also include sanitary accommodation and washrooms.

a. Stairs.

b. Lifts.

c. Escalators.

d. Chutes.

e. Ducts.

f. Pipes.

g. Additional provisions apply for both of the following.

i. Protected shafts that are protected stairways: Sections 2 to 5.

ii. Stairs that are also firefighting stairs: Section 17.

Construction of protected shafts

8.33 The construction enclosing a protected shaft (Diagram 8.3) should do all of the following.

a. Form a complete barrier to fire between the compartments connected by the shaft.

b. Have the appropriate fire resistance given in Appendix B, Table B3, except for uninsulated glazed screens that meet the provisions of paragraph 8.34.

c. Satisfy the provisions for ventilation and the treatment of openings in paragraphs 8.38 and 8.39.

Uninsulated glazed screens to protected shafts

8.34 An uninsulated glazed screen may be incorporated in the enclosure to a protected shaft between a stair and a lobby or corridor entered from the stair. The enclosure must conform to Diagram 8.4 and meet all of the following conditions.

a. The standard of fire resistance required for the protected stairway is not more than REI 60.

b. The glazed screen complies with the following.

i. It achieves a minimum rating of E 30.

ii. It complies with the guidance on limits on areas of uninsulated glazing in Appendix B, Table B5.

c. The lobby or corridor is enclosed with fire resisting construction achieving a minimum rating of REI 30.

8.35 Where the measures in Diagram 8.4 are not provided, then both of the following apply.

a. The enclosing walls should comply with Appendix B, Table B3.

b. The doors should comply with Appendix B, Table B5.

Pipes for oil or gas and ventilation ducts in protected shafts

8.36 A protected shaft containing a protected stairway and/or a lift should not also contain either of the following.

a. A pipe that conveys oil, other than in the mechanism of a hydraulic lift.

b. A ventilating duct. Two exceptions are as follows.

i. A duct provided for pressurising the protected stairway to keep it smoke free.

ii. A duct provided only to ventilate the protected stairway.

A pipe that is completely separated from a protected shaft by fire resisting construction is not considered to be contained within that shaft.

8.37 In a protected shaft, any pipe carrying natural gas or LPG should be both of the following.

a. Of screwed steel or all-welded steel construction.

b. Installed in accordance with both of the following.

i. The Pipelines Safety Regulations 1996.

ii. The Gas Safety (Installation and Use) Regulations 1998.

Ventilation of protected shafts conveying gas

8.38 A protected shaft conveying piped flammable gas should be ventilated direct to the outside air, by ventilation openings at high and low level in the shaft.
Any extension of the storey floor into the protected shaft should not compromise the free movement of air throughout the entire length of the shaft.

Guidance on shafts conveying piped flammable gas, including the size of ventilation openings, is given in BS 8313.

Openings into protected shafts

8.39 The external wall of a protected shaft does not normally need to have fire resistance. Situations where there are provisions are given in paragraph 3.29 (external walls of protected stairways, which may also be protected shafts) and paragraph 17.2 (firefighting shafts).

Openings in other parts of the enclosure to a protected shaft should be limited to the following.

a. If a wall common to two or more buildings forms part of the enclosure, only the following openings should be made in that wall.

i. A fire doorset providing a means of escape, which has the same fire resistance as the wall and is fitted in accordance with the provisions in Appendix C.

ii. The passage of a pipe that meets the provisions in Section 10.

b. Other parts of the enclosure (other than an external wall) should only have openings for any of the following.

i. Fire doorsets of the appropriate fire resistance, fitted in accordance with the provisions in Appendix C.

ii. The passage of pipes which meet the provisions in Section 10.

iii. Inlets to, outlets from and openings for a ventilation duct (if the shaft contains or serves as

a ventilating duct), meeting the provisions in Section 10.

iv. The passage of lift cables into a lift machine room (if the shaft contains a lift). If the machine room is at the bottom of the shaft, the openings should be as small as practicable.