Fire-fighting access and facilities
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Building Regulation functional requirements
- England and Wales
- Scotland
- Northern Ireland
Fire-fighting approaches
- External
- Internal
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- Buildings with a fire main and fire-fighting shaft
- Low-rise buildings without a fire-fighting shaft
- Fire-fighting procedures
Building Regulation functional requirements
England and Wales (Technical level 1)
Functional requirement B5 of the Building Regulations 2010 for England and Wales states:
(1) The building shall be designed and constructed so as to provide reasonable facilities to assist firefighters in the protection of life.
(2) Reasonable provision shall be made within the site of the building to enable fire appliances to gain access to the building.
Scotland (Technical level 1)
The Mandatory standards of the Building (Scotland) Regulations state:
Fire service access
2.12. Every building must be accessible to fire appliances and fire service personnel.
Fire service water supply
2.13. Every building must be provided with a water supply for use by the fire service.
Limitation – This standard does not apply to domestic buildings.
Fire service facilities
2.14. Every building must be designed and constructed in such a way that facilities are provided to assist fire-fighting or rescue operations.
Northern Ireland (Technical level 1)
The Building Regulations (Northern Ireland) 2012 state:
Facilities and access for the Fire and Rescue Service
37 (1) A building shall be designed and constructed with such reasonable facilities as are necessary to assist the Fire and Rescue Service in ensuring the safety of people in and about the building in the event of a fire.
37 (2) Reasonable provisions shall be made within the boundary of the premises for access to the building by fire and rescue appliances for the purpose of paragraph (1).
Fire-fighting provisions in buildings
This section outlines different approaches fire and rescue services may employ when arriving at a building, and the measures that can be incorporated into the design to minimise risk to them. There are National Operational Guidance documents available for the different hazards fire fighters might face.
To ensure the safety of fire and rescue services attending a fire, it is necessary to consider the risk presented to them. When designing or constructing with timber it is important to identify and propose measures to assist with this risk assessment and mitigation.
Fire-fighting approaches
External
The fire service takes steps to control the fire from outside the building by deploying fire-fighting media, usually water, via hoses to bring the fire under control and limit the risk of fire spread to adjacent buildings. This approach is often used when conditions within the building – such as the fire dynamics or the stability of the structure – mean it would be unsafe for fire-fighters to enter, and where there are no people inside the building to be rescued.
An external fire-fighting approach will rely on perimeter access to the building for pump or high reach fire appliances, dependent on the height of the building. A standard fire appliance can be used for buildings with a height of 11 m, while specialist aerial appliances can reach a height of 32 m (refer here). As not all fire services will have access to high-reach appliances, engagement with the local fire service is essential where building designs are based on the availability of specific fire-fighting capabilities.
To support external fire-fighting in small buildings, the perimeter access and hose distance requirements should be followed. As the minimum provisions in the statutory guidance are for “common buildings”, it may be necessary to provide stricter requirements for mass timber buildings.
Internal
Fighting a fire from the inside of a building is usual for high-rise buildings where external fire-fighting approaches are no longer feasible, or for buildings where there is a greater likelihood of occupants being trapped inside due to unfamiliarity with the building.
A high-rise building will be divided into zones, such as ‘bridgehead’ – i.e. the safe area/zone inside the building from where to stage fire-fighting interventions that respond to the site and situation-specific hazards.
Fire-fighting approaches differ depending on the presence of fire-fighting shaft.
Buildings with a fire main and fire-fighting shaft (Technical level 1)
Low-rise buildings without a fire-fighting shaft (Technical level 1)
All areas of a building without a fire-fighting shaft must be within reach of a fire-fighting hose – 45 m. To enter this kind of building, fire and rescue services must have certainty that the structure will be safe for the duration of their operation inside the building.
Fire-fighting procedures (Technical level 1)
The fire service should be consulted by the design team in the early stages of design (e.g. RIBA Stage 2), to understand fire-fighting operational procedures and how these may be carried out for the building.
Hazards and associated mitigation measures
The section below lists specific hazards presented by the use of mass timber in the design and construction of buildings, and how those hazards could impact on fire-fighting duties. It is important to note that, whilst the hazards of mass timber may be common to different building uses and heights, the consequences of a fire scenario can differ. For example, the use and occupancy characteristics of a four-storey residential building are different from those of a four-storey office building. A low-rise office with simultaneous evacuation presents a lower likelihood of harm occurring than a residential building with sleeping occupants; and the mitigation measures required to control the resulting risks to an acceptable level will differ.
Hazard – Smouldering hotspots
Timber fires are prone to smouldering hotspots where combustion continues without presence of a flame. Smouldering can occur after the fire service have attended the site and have extinguished the flaming combustion, and can lead to significant structural damage and even re-ignition. It is particularly hazardous, as smouldering may go unseen, and therefore not be addressed until the damage has already occurred. A recent large scale compartment test in a mass timber structure illustrates the hazard (see large CLT compartment experiments).
Smouldering combustion can be dangerous both for the safety of occupants and for the structure as a whole, and can lead to the fire service having to deploy more resource to monitor potential hotspots and check for re-ignition, and if it occurs, re-enter the building again, putting themselves at risk again.
Mitigation approach - Early fire service involvement during design
The fire service should pull back linings to check for smouldering where timber is present so that water can be applied.
The use of thermal imaging cameras can be employed to help identify smouldering hotspots. However, thermal imaging cameras are not readily available to all fire services, and so their availability should be confirmed with the local fire and rescue service.
Early involvement of the fire and rescue service during design will allow the design to be developed to take into consideration the fire service’s existing practices to address smouldering, and the limitations of their equipment.
Mitigation approach - Encapsulation of cavities
Whilst thermal imaging cameras are effective in identifying hotspots if they are accessible, they have limited use in restricted access areas. If the design has, for example, a cavity hidden behind a decorative partition, a thermal imaging camera may not be able to detect a hotspot within the cavity. Additionally, cavities and voids can create a channel for undetected fire spread through the building, as further discussed below. This can be minimised by avoiding concealed spaces, voids or cavities within a design.
Mitigation approach - Provision of non-combustible firefighting shaft
The provision of a non-combustible firefighting shaft will provide fire-fighters with a safe place to retreat to, in the knowledge that smouldering combustion will not occur within the construction of the firefighting shaft.
In the case of a fire in a high-rise building, the UKFRS advise that the bridgehead be set up two floors below the lowest floor of the building that is affected by the incident, as per the National Operational Guidance on Vertical Sectors. The firefighting lift will be used to access up to this floor; beyond which operations will rely on the stairwell to access the fire floors. In this case, the safety of the core will give fire-fighters greater security as they travel between the fire sector and bridgehead, and help to ensure crews can follow their procedures with confidence.
Hazard – Hotter, longer fires with greater external flaming: (specifically relevant to mass timber building)
Timber is a combustible material and when exposed can add to the fuel load of a building. This can lead to hotter, longer fires, with greater external flaming. A longer fire can result in more onerous conditions for fire-fighters within the building, whether fighting the fire or rescuing trapped occupants.
Greater external flaming can mean that the fire service have to fight the fire from the floor above, resulting in an alteration of their operational methods. Such deviations can lead to complications, as the fire service may have less experience in them.
Mitigation approach - Automatic detection
For a timber building, the inclusion of automatic detection, even where not required by legislation/guidance, will help to detect a fire in the early stages of development, and initiate the evacuation process.
Early detection can also allow the fire service to be called earlier and increase the likelihood of their intervention before the fire has had time to grow in intensity. The size of the compartment is a key factor and can lead to fully developed fires even with swift fire brigade activation.
Mitigation approach - Reduced compartment sizes
Whilst Scottish legislation limits the maximum total area of any compartment based on the building use, English, Welsh, and Northern Irish guidance do not place restrictions on compartment sizes for certain building types, such as offices. In all cases, the design should consider whether the compartment size can be reduced to limit fire size. As exposed timber can contribute to fire intensity, reducing compartment size manages available fuel load and limiting fire spread. This will improve conditions for fire fighters.
Mitigation approach - Sprinklers
Automatic fire suppression systems, such as sprinklers, can control a fire before the fire service are called and arrive at the building. In some cases, sprinklers can extinguish the fire, thus reducing reliance on the fire service. In cases where the fire isn’t extinguished by the sprinklers, its spread and size will be reduced. This will allow fire-fighters to tackle the fire more safely, particularly where an internal fire-fighting approach is likely to be required.
Mitigation approach - Encapsulation
Encapsulation can prevent timber from becoming involved in a fire, ensuring it does not contribute fuel to the fire, which can make it spread more rapidly.
See Structural design approaches for the performance requirements of encapsulation.
Mitigation approach - CLT Adhesive
The type of adhesive used in CLT can influence the fire dynamics in the building, with some adhesives softening in high temperatures resulting in glue line integrity failure and fall off of protective char, which allows fresh timber to become available as fuel, see also Load-bearing timber wall and floor assemblies. Specifying CLT with a heat-resistant adhesive needs to be considered in the design.
Hazard – Fire during the construction phase
While a building is under construction, not all active and passive fire protection measures will have been installed and commissioned.
Mitigation approach - Risk assessment
To ensure the hazards presented during construction are adequately mitigated to provide a tolerable risk level, a fire risk assessment should be undertaken. The measures presented in this table can assist with controlling the risks associated during construction. See Fire safety during construction for guidance on fire risk assessments during construction.
Hazard – Insufficient water provisions
Exposed mass timber surfaces can contribute to a fire as fuel and as a surface for flame spread. Consequently, fires may be larger in terms of heat release rate and spread distance, requiring more water, over a larger area.
When compared to buildings with non-combustible linings, a building with exposed timber surfaces in very large compartments could need significantly more water for fire-fighters to advance safely in the fire compartment.
Mitigation approach - Provision of additional fire-fighting water supply
For buildings reliant on internal fire-fighting procedures, and where mass timber is exposed, consideration should be given to the provision of wet fire mains, rather than dry fire mains. Additionally, as part of the design fire risk assessment process, consideration should be given to increasing the capacity of the wet riser and tanks to allow fire-fighting activities on multiple floors (i.e. four or six fire-fighting jets operating simultaneously; 2 to 3 times the requirement outlined in BS 9990).
Hazard – Modern Methods of Construction
Timber is not a new construction material and has been studied and used in construction over a long time. However, the use of mass timber, such as large CLT panels forming walls and floors, is relatively new; fire-fighters may not expect the presence of mass timber, or may have limited experience fighting fires in mass timber compartments.
Mitigation approach - Early fire service involvement
The use of exposed mass timber in structural elements and compartmentation should be communicated to the fire service to allow them to record the information in their building database systems and develop specific operational plans as necessary. Further, simple drawings showing the extent of mass timber should also be included in the premises information box.
To enable the above, the fire service should be consulted during the design process. Additionally, the fire service can be invited to undertake familiarisation visits during the construction and operation of the building.
The extent to which the above is required should be assessed as part of the design fire risk assessment based on the use and complexity of the building.
Hazard – Concealed spaces, cavities and voids
Concealed spaces, cavities, and voids can provide a channel through which fire can spread unseen.
Depending on the size of the void, automatic detection may not be required. This could lead to undetected fire spread resulting in a larger, more developed fire before the fire service are called. The fire service must thus tackle a larger and hotter fire than if the ignition had been detected at an earlier point, before being allowed to spread through the building via the voids.
Mitigation approach - Removal of voids
In many cases, the best way to prevent fire spread through concealed spaces, cavities and voids is to remove them altogether. For mass timber buildings, where cavities remain, spaces should be encapsulated to mitigate the timber contributing to fire. Given the limited accessibility to concealed spaces, reliance on identifying hotspots using thermal imaging should be avoided. Applying water to a concealed space may also be difficult.