Tweaking with the symptoms and ignoring the cause: Sprinklers in high-rise residential buildings
Following the government’s proposal that sprinklers have a reduced threshold for installation in new residential buildings from 30m to 18m, FIRE Correspondent Tony Prosser speculates on the reasoning and implications for residents.
Sometimes the terminology we use can have a dramatic effect on the way things can be perceived by those less familiar than ourselves with the technological meaning and nuances of the words and the way they are assembled. As an example, the Ministry of Transport could declare a specific make of car to be a ‘higher risk vehicle’ or the Department of the Environment, Fisheries and Food may declare that the Maris Piper is a more dangerous potato than the King Edward. While both could be theoretically true, the person on the street could start to panic if they own a higher risk vehicle or ate King Edwards at every Sunday lunch.
In a similar way fire officers’ public pronouncements that buildings which are built in a certain way are not safe can lead to less informed individuals to believe that they live in “death-traps”. Recent comments regarding the viability of the widely criticised ‘stay put’ policy threatens to cause serious consternation amongst those living in high-rise blocks of flats. This can create a real problem for fire and rescue services which now have to manage expectations that a “normal” fire within a high-rise block now constitutes such a risk that evacuation of large parts of the block is essential with all the potential challenges that entails. Higher risk high-rise buildings (HRHRB) is another term that may lead to concern for those who have to live there. In recent months, fire safety inspectors have examined 216 buildings in London and cancelled the ‘stay put’ policy within those buildings. This creates a problem for the landlords, tenants, fire and rescue inspectors and not least, the government.
High Risk High-rise Buildings
Since the fire in Grenfell Tower, suggestions for improvements for fire safety in tower blocks have included improvements in alarm systems, major structural changes within the buildings, and the installation of fire sprinkler systems. Notwithstanding the most obvious solution, the banning of combustible materials on the external coverings which could lead to rapid extension fire on all premises, it is sprinklers that have, rightly, tended to capture the imagination and focus of much debate within large parts of the community and fire industry as the solution to all the problems in HRHRBs.
The current requirement (since 2007) is for all residential buildings of over 30m high to be fitted with automatic sprinkler systems. The government is currently undertaking a consultation on ‘sprinklers and other fire safety measures in new high-rise blocks of flats’ which is due to close on November 20. It also includes seeking views on other fire safety measures including improvements to ‘wayfinding signage’ in blocks of flats, and the provision of evacuation alert systems for use by fire and rescue services (as is already the case in Scotland) to evacuate floors of the building.
It is proposed that sprinklers have a reduced threshold (or trigger height) for installation (only) in new residential buildings from the current 30m to 18m. The original reason for both the 18m and 30m thresholds appears to be lost in time. Nowhere within the explanatory notes for Approved Document B (ADB) under Building Regulations legislation explains why this is the case. The best explanation the author has found to date is that 30m is approximately the height of an extended turntable ladder (TTL), hydraulic platform (HP) and aerial ladder platform (ALP). The London Building Acts, which many councils imitated in fire safety terms, certainly appear to follow this maxim of ladder height as illustrated in the 1939 amendment Section 20 of which then restricted building heights to 100 feet without further consent, the TIL then being around.
So it looks as though escape by ladder was used as some guide in fire prevention building control. I suspect the London County Council and Fire Offices Committee were a major influence in all of this. If is indeed the case, then the rationale for this measurement is that fires in high-rise buildings could be tackled using external jets or monitors from these vehicles. This of course presupposes that these buildings have been built to a suitable standard of construction which means that a ‘stay put’ policy is appropriate and that the fire will not be blown into other parts of the building through weak doors and walls.
It has been the case in some buildings built since 2007, that the construction methods and standards of installation are so poor that the effect of an external jet would be to drive the fire into unaffected parts. The origin of the 18m threshold is even more obscure and despite trawling the internet and the memories of former and current fire safety experts, the only consistent response is that 18m is the height reached by a 50ft wheeled escape to which a 13ft hook ladder could be attached: 18m being 59ft, 0.661 inches.
Sixty feet was referenced in the London Building Act of 1894 since this early building code required additional safety measures in buildings over 60ft because rescues were beyond the fire brigades ladders.
Fire Disaster Catalyst
It was also possible that the catalyst driving the 60ft into codes across the UK was the Queen Victoria Street fire in London on June 9, 1902 when the brigade was unable to rescue workers trapped on the fifth floor in a workshop and nine people died, eight being young girls. The girls seen waving arms hopelessly from windows was witnessed by ‘thousands’. The escapes were too short and following the coroner’s inquest, recommendations and conclusions were made that resulted in the 60ft standard being reinforced retrospectively in London and copied across the country by many fire brigades in metropolitan industrialised Britain.
Eighteen metres is also the threshold for the installation of dry risers, the means of getting water to an upper storey fire beyond the capability of a wheeled escape arrangement and where a TTL cannot gain access. This arcane knowledge (or guesswork – I am still not convinced) may be irrelevant as a proposal has also been made for the threshold for installation at 11m, the approximate usable height that a 13.5m extension ladder can be used. This equates to a generous three floors above ground or a more parsimonious (and more likely given a higher number of homes per unit footprint requirement in the 21st century) four floors. But even at four floors, in a residential block of apartments, a fire in a lower floor could lead to the evacuation or entrapment of large numbers of individuals on up to three floors above ground.
Perhaps 11m as a threshold is too high and that it should be reduced to any building with floors above 4.5m, according to ADB, the height above which individuals are not expected to self-rescue via windows. If we consider the fire at Beechmere assisted living home in Crewe, mentioned in last month’s issue of FIRE, that unsprinklered building only consisted of three storeys. The fire, which occurred in late afternoon, destroyed the whole building but if it had occurred during the dark hours it could have resulted in multiple fatalities.
A residential dwelling block of the same construction (timber framed) and height would not require sprinklers under the new proposals despite the fact self-rescue would not be possible from the uppermost story of this building. Ministry for Housing, Communities and Local Government (MHCLG) research estimated a reduction in deaths and injuries of 76 per cent and 50 per cent respectively where sprinklers are provided. Other research has shown these figures can be even higher.
Irrespective of the origin of the levels at which the proposed and existing heights are set, it is clear that cost will inevitably play a factor in the eventual outcome that the government will determine. Work done by the British Fire Sprinkler Association in 2013 demonstrated the low costs of retro installation of sprinklers. Callow Mount, a 13 storey, 48 flat residential block in Sheffield was retrofitted with sprinklers in all flats using flat wall sprinkler heads and pendant heads in service areas, lobbies, ground floors and bin stores. Overall cost for the installation, factoring in original installation, maintenance and servicing for the life of the sprinklers – 30 years – was calculated as being between £40 and £50 per year. This is slightly less than what the content insurance would be for each flat.
There are downsides to this project, as there would be with any retrofitted installation: while the sprinklers themselves are effective with respect to cost and efficacy, they do look like what they are: a bolt-on to the original building with unattractive boxing covering pipe runs in corridors. Even within flats themselves the sprinklers are exposed, as is the piping within the room, leaving occupants in no doubt as to how they are being protected. Nevertheless, as a guarantee of providing reassurance for residents within these blocks and as a proof of concept experiment, they work. With a new impetus being given to the retrofitting of sprinklers in many high-rise blocks, this may be a low cost solution to sprinkler installation that is affordable for local authorities, housing associations and even private residential blocks.
While there is no mandatory requirement for the retrofitting of sprinkler installations within existing premises, it is nevertheless likely that there will be pressure upon the owners of all existing premises to start considering these measures. It will be interesting in the next few years to find out how government expectations will be manifested as to how fire risk assessments of high-rise blocks are expected to take into account the use (or not) of sprinklers within this premises.
Installations in new buildings are obviously expected to be more expensive and estimated costs have been given as being between 1.5 per cent and three per cent of the total building cost. The Business Sprinkler Alliance has calculated the cost of sprinkler installation in a two to five star hotel building (the nearest compactor and potentially a guide cost for a new build residential building) as being between £20 and £30 per m2. MHCLG has estimated that in the next ten years 1,970 new builds will come within the requirements of the regulations if the 18m threshold is adopted. This would incur a cost of between £270 and £380 million over that period. If the height threshold were reduced to 11m, 15,940 newbuilds would require systems fitted. This would increase the cost to between £1.36 billion and £1.93 billion.
Even where sprinklers are fitted, success is not always guaranteed and it has been recognised that additional measures may be required. The fire in the Lacrosse Docklands building in La Trobe Street, Melbourne Docklands district in November 2014 was notable for a number of reasons. The fire started at 02.24 in a balcony area on the eighth floor of a prestigious 23 storey tower block. On arrival of the first firefighters five minutes later, the fire had spread vertically six floors. At 02.35, crews reported that the fire had spread to the roof involving 16 levels above that of the ignition location. Aluminium composite cladding incorporating combustible materials was used in the building and believed to have contributed to the fire. Four hundred people were evacuated from the building due to the external spread of the fire and entry to the building at many levels. Fortunately, 26 sprinkler heads actuated over all 16 floors involved in the fire, usually within the lounge and/or bedroom areas – this prevented spread into the other parts of the building.
The actuation of so many heads put a strain upon the system, especially when two hydrants fed off the same main were in use but it was concluded by Melbourne Fire Department that the system operated far beyond its designed capacity. This incident raises some interesting aspects of the use of sprinklers as a single solution to high-rise building fires. The first is the degree to which sprinklers are required on balconies. The Building Code of Australia requires that ‘Portions of covered balconies that exceed 6m² floor area and have a depth in excess of 2m shall be sprinkler protected’. The balconies were 1.8m deep and so did not require sprinklers to be installed.
The fire at Samuel Garside building in Barking, which was not fitted with sprinklers on the balcony (or anywhere else – it was below the current threshold of 30m) but it could have had a different outcome if it had been. Furthermore, if a fire were to spread across the surface of a building and enter several rooms within several flats, would the design of an automatic sprinkler system take into account the additional water flow and pressure requirement of this scenario? The overengineering of the system in the LaCrosse Building delivered unexpected but nonetheless great benefits in November 2014.
How many UK builders would go above the minimum requirements in any building regulations document “just in case”? We should not hold our breath. Which brings us back to the 216 buildings in the capital which now have no ‘stay put’ policy. What solutions are available to eliminate the need for such a measure? Well firstly, the sprinklers, the design of which is proposed through ADB, is to comply with the requirements of British Standard BS 9251. Currently, ADB does not require sprinklers in stairs, corridors, or landings and the government states that while its intention is to provide ‘Fire suppression systems in areas with those fires are likely to occur’, these areas will be excluded. This can create a real problem because while accidental fires tend not to occur in these excluded areas, deliberate ones can and often do.
A couple of years ago in the West Midlands a fire occurred in the lift lobby of a 34-storey building when a tenant, moving out, left most of the contents of their flat in the lobby for a short period, which caught fire. Firefighters were confronted by a fully involved compartment fire in the lift lobby. While not an everyday occurrence, unexpected locations for fires are not unusual and for the sake of a small additional investment, 100 per cent coverage could be achieved and both tenants, landlords and fire and rescue services would be we are assured of safety levels within the premises.
Other considerations being consulted on include wayfinding signage for fire and rescue services. During the search and rescue operations in buildings, signage helping firefighters to identify, search and record which rooms have been searched and cleared would help avoid repeating searches that can occur within smoke logged corridors and stairs. Several options are suggested including painted numbers, powered luminaires and photo luminescent signs, any of which, if followed will assist searching the building.
An additional practical consideration that is not included in the consultation is the introduction of a standardised numbering methodology of floors and flats so that flat 72 is the second flat on the seventh floor and not a flat on the ninth floor. Firefighters have lost their lives partly as a result of idiosyncratic flat numbering and now would be the ideal time to address this problem.
Evacuation of whole floors or buildings has become a major issue following the Grenfell Tower fire. Again, Scotland has stolen a march on the rest of the country and is shortly introducing such an evacuation system with standards currently being developed. The MHCLG consultation has asked if such systems are required and at what height threshold should they be introduced, particularly when the cost with an 18m threshold will be £100 million to £130 million over ten years and between £440 million and £510 million over ten years if applied to flats over the 11m threshold. Considerations already identified include the capacity of most staircases in high-rise blocks which could be lead to overcrowding, compromising of ventilation systems when doors are opened continually etc. When considering evacuation, the risk of dying may be greater in escape routes as evacuees are subject to smoke in compromised escape routes.
Despite the controversy associated with ‘stay put’ policies, for the vast majority of buildings they have performed well. At the lobby compartment fire in the West Midlands, people for the most part stayed in their flats and no serious injuries were reported. At a fire in Portsmouth some months before, operational difficulties delayed entry into the compartment where a fire had been burning for 45 minutes without breaching the fire doors. Of course, neither of these buildings were wrapped with materials that are inherently combustible. Perhaps, once again we are in danger of treating the symptoms and not the cause. Banning the use of combustible materials in the cladding of buildings of any height and enforcing the ban through a properly funded inspection regime would be a lot cheaper. The hazard would be removed and residents in one of the 216 tower blocks in the capital where ‘stay put’ is no longer suitable would not have to worry (so much) about their safety.
If anyone does know the definitive answer to the 18m and 30m thresholds, please forward to the email address below.
Thanks to Dennis Davis, Executive Officer for the Fire Sector Federation for additional information provided for this article.
Write a Comment