11.3.5 Behaviour in relation to fire
Volumetric systems shall have adequate fire resistance and resist the spread of fire and smoke in accordance with Building Regulations. Issues to be taken into account include:
- cavity barriers and fire-stopping
- services
- fire resistance of the unit
- movement.
Guidance within supporting documents to the Building Regulations should be fully considered in the design and construction of volumetric systems.
The design and System Manual should clearly define:
- the overall fire protection strategy of the system
- which elements of fire protection are either factory or site installed.
11.3.5.1 Cavity barriers and fire-stopping
The provision and installation of cavity barriers and fire-stopping should:
- be specified to accommodate design, manufacturing and installation tolerances
- be in accordance with the Building Regulations and the design
- be designed to accommodate ventilation or drainage paths
- be used in accordance with manufacturers recommendations
- account for movement in the frame.
Detailing and specification of cavity barriers and fire-stopping should be in accordance with the manufacturer’s recommendations and supported with representative test evidence.
Moisture protection should be provided to horizontal and vertical cavity barriers.
Where cavity barriers or fire-stopping cannot be easily replaced they should be specified in accordance with the design life of the building.
Buildings incorporating volumetric units may have significant concealed cavities between units. The building design should consider appropriate subdivision of cavities at horizontal and vertical junctions of volumetric units and between volumetric units and surrounding construction. Fire-stopping should be provided where necessary at junctions, to complete lines of compartmentation.
Factory installed cavity barriers or fire-stopping may be damaged or dislodged during the transportation or installation of volumetric units on site. Manufacturers and installers should allow for suitable access to inspect and verify concealed cavity barriers and fire-stopping post-installation.
When providing cavity barriers and fire-stopping:
- fire-stopping should be specified and sized to accommodate dimensional and installation tolerances of the unit
- gaps between compartments should be sealed
- presence of temporary weather protection membranes should not affect the performance, and should be removed unless tested or approved by the design.
At compartment walls fire-stopping should be provided to seal any gaps between the underside of units and the tops of foundations or substructure walls.
11.3.5.2 Services
Only the services shown in the design should be installed in volumetric system floors and walls, and:
- service outlets should not impair the fire resistance of floors and walls
- service mains should not passthrough separating wall cavities.
11.3.5.3 Fire resistance of the unit
All building elements should have adequate fire resistance in accordance with Building Regulations, supported with representative test evidence and supporting engineering assessments to appropriate standards.
The design should specify:
- whether primary structural members require individual encasement or are protected by fire-resistant linings to the wall, floor, or ceiling frame
- details of junctions of secondary attachments to the primary structural frame and how fire resistance is maintained
- details of service openings, voids, and penetrations
- details demonstrating that columns and beams, where provided, are protected on all sides for the full height or width, including connections to other structural members, and how protection is maintained where the members extend through a ceiling or floor voids.
Where units join together and continuous linings are required or where access points are left open to facilitate connections, internal fire-resisting linings should be:
- installed with minimum laps in accordance with manufacturer’s recommendations, or
- in accordance with the design and supported with representative test evidence to appropriate standards.
11.3.5.4 Movement
Fire-stopping should be specified and designed to accommodate anticipated movement in the building structure.
Where units are connected to surrounding construction, differential vertical movement should be considered in the design and specification of suitable fire-stopping and cavity barriers.
Non-loadbearing infill walls within volumetric units should accommodate anticipated deflection within the primary frame in accordance with the design. Should these walls be fire resisting, detailing at the head should be such that performance in this regard is not compromised
Last updated: 2nd January 2025