Service risers are critical vertical shafts that carry vital building services such as electrical cabling, plumbing, communication cabling, firefighting water pipes, and HVAC systems. Because they penetrate multiple floor levels, they can pose a risk for vertical fire spread. Effective fire-stopping in these areas is essential to maintain compartmentation and protect occupants and assets.
Fire-stopping in service risers – what you need to know
The fire strategy for a building outlines the fire-resisting requirements for walls, doors, floors, and structural members, as well as fire detection and prevention systems. Temporary fire-stopping during the construction phase may also need to be considered once the building has become fully enclosed by the outer façade. Key regulatory inputs include:
- Building Regulations 2010 – Approved Document B (Fire Safety) (mandatory)
- Joint Code of Practice (JCoP) -V10.2 (recommendations by the Fire Prevention Association and industry bodies)
- Legislation referenced: Regulatory Reform (Fire Safety) Order 2005, Fire Safety Act 2021, and Fire Safety (England) Regulations 2022.Â
Fire resistance is measured in two key aspects:
- Integrity (E): Prevents fire from breaching the firestop
- Insulation (I): Limits heat transfer across the firestop.
To pass insulation tests, the temperature on the non-fire side must not exceed 180°C plus ambient temperature at the time of test – often a more challenging criterion than integrity.
The fire-stopping strategy for risers centres on compartmentation. Typical ways of achieving this are:
- Vertical compartmentation of the entire shaft with a wall and door rating of 120 minutes
- As above but with horizontal fire-stopping at intervals – often every 10 floors
- Horizontal fire-stopping at every floor level – often for high-risk service types or to reduce the required horizontal fire rating to 90 minutes or even 60 minutes.
Fire detection and prevention systems will be required at the head of every shaft or just below where horizontal fire-stopping takes place. It’s perhaps important to note that if horizontal fire-stopping is adopted at every floor level, there may be a requirement to provide fire detection and prevention measures within each floor level – a not insignificant extra cost to the project.
Common ways of achieving fire-stopping for walls include:
- Solid concrete cores or main structural walls – often used in high-rise construction
- Dense and lightweight blockwork
- Metal or timber stud walls with layers of fire-resisting board cladding to each side.
Manufacturers will all have test data to inform the design needed to achieve the correct fire-resisting duration.
The top of each wall head will need to have a fire-resisting deflection detail to accommodate movement of the floor, beam, or wall above. Beams for supporting walls will also need to be clad to achieve the same degree of fire resistance. As an alternative, Comtec has developed the WallBeam – a fireproof structural beam that integrates within the riser cassette to support riser partition walls. This unique product also incorporates heat deflecting angles to provide effective fire-stopping in the defection head detail at the top of each wall interface.
Methods of achieving horizontal fire-stopping for floors also vary – from using layers of mineral wool batts under steel mesh floors to forming a tray for pourable and settable fire-resisting compound. Comtec has developed the AlphaRiser FR unit – a pre-manufactured fire-stopping floor unit that uses a unique DropBracket system to lower the riser floor when required, providing a 100mm ‘tray’ to accommodate installation of a structural fire compound. During testing, this achieved 4 hours of resistance for both Integrity (E) and Insulation (I), meeting the general requirements of BS EN 1366-3.
In conclusion, effective fire-stopping in service risers is a vital part of a building’s fire strategy. By following regulatory guidance and using tested systems, designers and contractors can significantly reduce the risk of fire spread through vertical shafts.
For more information, reach out to Comtec’s technical team for guidance and support at sales@comtecgrp.com.
