CROSS Safety Report
Fire resistance of multi-storey car parks
This report is over 2 years old
A reporter visited a recently constructed car park which contained some of the same design issues discussed in the February 2018 Standing Committee on Structural Safety (SCOSS) Alert on Fire in Multi-Storey Car Parks.
They find it difficult to believe that the car park they visited could survive for significantly more than 15 minutes in a fire without collapsing.
Key Learning Outcomes
For design engineers and building control:
Be aware that a multi storey car park structure designed to withstand fire for 15 minutes may not satisfy the functional requirement of the building regulations
Structures should be designed to remain in a safe and stable condition in the event of a fire to allow firefighters to safely enter the building
Consider the risk of fire spread to neighbouring buildings and the risk of structural collapse outside of the building footprint
Be aware of past failures and take them into account when designing or altering similar structures
For car park owners and managers:
Regular inspections and maintenance of fire protection systems can help to detect any safety issues which may need addressing before they become hazardous
Fire safety inspections and assessments should be carried out by a competent person with relevant knowledge and experience
Find out more about the Full Report
The Full Report below has been submitted to CROSS and describes the reporter’s experience. The text has been edited for clarity and to ensure anonymity and confidentiality by removing any identifiable details. If you would like to know more about our secure reporting process or submit a report yourself, please visit the reporting to CROSS-UK page.
The February 2018 SCOSS Alert on Fire in Multi-Storey Car Parks highlighted the risk of fire spreading between cars in a multi-storey car park. Fortunately, the car park where that fire occurred was constructed of reinforced concrete. This provided a fire resistance considerably greater than the minimum 15 minutes required by Approved Document B to the building regulations.
However, according to the Merseyside Fire & Rescue Service Protection Report on the fire, the use of slots in the floors for drainage, combined with aluminium gutters and PVC downpipes allowed the fire to spread rapidly between floors and the structure was severely damaged.
New car park with similar design issues
The reporter visited a recently constructed car park which contained some of the design issues discussed in the Merseyside Fire & Rescue Service Protection Report. They find it difficult to believe that this car park could survive for significantly more than 15 minutes in a fire without collapsing.
The reporter visited a recently constructed car park which contained some of the design issues discussed in the Merseyside Fire & Rescue Service Protection Report. They find it difficult to believe that this car park could survive for significantly more than 15 minutes in a fire without collapsing
If a fire similar to the December 2017 Liverpool fire occurred in this car park, the reporter feels it is likely that it would spread even more rapidly. They feel that after little more than 15 minutes, floor areas and the structural frame would begin to fail. This would allow burning cars to fall on to the deck below and complete collapse of the structure would probably not take long
They go on to say that if the fire did spread rapidly, then firefighters could not enter the building to try to put the fire out, because of the danger of collapse. This would negate the assumption behind the 15-minute fire rating for multi-storey car parks, which is that firefighters should be able to get in and extinguish a car fire before it spreads to more than 2 or 3 vehicles.
Risk of fire spread to neighbouring buildings
The reporter also highlights that if the structure were to collapse, it might not collapse tidily onto its own footprint, and could instead fall laterally, discharging burning cars on to the ground well outside of its own footprint.
The reporter concludes that despite the publication of the SCOSS Alert in February 2018, this form of construction is still permitted by Approved Document B to the building regulations and could be used for multi-storey car parks up to 30 metres high.
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This report raises a valuable point as to whether the current Approved Document B fire resistance ratings are enough to achieve the robust design of fire-resistant car parks, however it presents element Fire Resistance Ratings as being the same as the Structural Fire Resistance.
This is an important distinction to make in my view as the common misconception of the rating system is that the fire resistance rating (i.e. R30) means that the structure is designed to allow collapse after 30 minutes of fire exposure, this is not the case. From my understanding, Approved Document B provides the fire-resistance rating of a structural element based on the length of time that it performs satisfactorily in the standard furnace test. i.e. a resistance of 15 minutes means that the element in question will resist the standard furnace test temperature curve for a minimum of 15 minutes before failure under a predefined set of loading conditions. This is not to say the same element will resist a real fire for 15 minutes before failing but is simply a way of standardising fire resistance testing and specification across the industry.
The true length of time a structure may last during a fire is related to the individual temperature – time relationship of the individual fire which, in turn relies on the quantity of fuel available to a given fire. This leads to a structural failure time that may be higher or lower than the resistance rating obtained by the standard furnace test.
It is conceivable that the misconception that a fire resistance rating relates directly to the length of time before structural collapse could result in the dangerous scenario that firefighters are given false information on the overall fire resistance of a structure. This article provides a good overview of this topic: Structural fire resistance: Rating system manifests crude, inconsistent design.
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It is disappointing to hear that the lessons from the Kings Dock car park fire in December 2017 are in some cases not being learned for the design of new car parks. The SCOSS Alert on Fire in Multi-Storey Car Parks was published to help those who own, commission, design, construct, or maintain multi-storey car parks to learn the lessons from this event.
Recent car park fire incidents
As recently as September 2019, there was a severe fire at a multi-storey car park in Cork, Ireland, which destroyed up to 60 cars. It was reported that the blaze quickly spread to other cars in the area. A worrying trend of severe multi-storey car park fires may be developing.
In February 2018, there was a car fire on the 7th floor of the 100 storey John Hancock Centre in Chicago. The fire was controlled by sprinklers until the fire services arrived, possibly preventing its spread to other vehicles.
CROSS worked with the British Parking Association (BPA) to submit evidence to the technical review of Approved Document B of the building regulations in March 2019. This called for further research to be conducted into the risk of fire spread in car parks.
In September 2019, the Ministry of Housing, Communities and Local Government (MHCLG) published the analysis of responses to the call for evidence, which for car parks stated that:
The report states that the government will work with industry and the Building Regulations Advisory Committee (BRAC) to consider the full range of technical areas raised in the call for evidence. They will also determine a detailed plan for taking this review forward.
Structures must comply with all the building regulations
The reporter mentions compliance with Approved Document B, but it is important to remember that the structure must comply with the building regulations themselves. In particular, Regulation 8, Limitation on requirements, states:
The reporter mentions compliance with Approved Document B, but it is important to remember that the structure must comply with the building regulations themselves.
Note that Regulation 8 requires the health and safety of those ‘about buildings’ and ‘who may be affected by buildings’ to be safeguarded as well as those ‘in’ buildings. Safety depends on assuring the structure possesses certain attributes.
One of these is to permit the safe escape of occupants. However, as the reporter points out, safety for firefighters, minimising the risk of fire spread to neighbouring buildings and risk of structural collapse outside of the building footprint are others.