The Grenfell Tower fire, the worst in the UK for almost a century, claiming 72 lives, has focused the world’s attention on how countless numbers of high-rise buildings are threatened with the prospect of failing fire safety standards. In the wake of the tragedy in June last year, the Hackitt report has proposed sweeping changes that, if implemented, would fundamentally shake up the regulation and management of building safety.
In her introduction to the report, ‘Building a Safer Future – Independent Review of Building Regulations and Fire Safety: Final Report’ (https://is.gd/zeyadi), delivered in May this year, Dame Judith Hackitt, who led the review, states: “At the heart of this report are the principles for a new regulatory framework which will drive real culture change and the right behaviours. We need to adopt a very different approach to the regulatory framework covering the design, construction and maintenance of high-rise residential buildings which recognises that they are complex systems where the actions of many different people can compromise the integrity of that system.”
In particular, the report argues, a high-rise dutyholder will be responsible for maintaining what is referred to as the ‘golden thread’ of information about the building structure and materials, detailing the maintenance, testing and inspection routine, as well as how fire risk assessments have been undertaken and actions implemented. Where no records already exist, it argues that the dataholder will have to conduct surveys to “reconstruct the design intent” for building safety, particularly with regard to fire.
As the report goes on to state, the dutyholder will have to undertake an information-gathering exercise to build the data record and reconstruct the design intent for building safety. “This may require invasive surveys (where parts of the construction are opened up, if necessary). While many building owners and landlords are rightly starting this work now, many (including local authorities and housing associations) will have a portfolio to work through which may take some time.”
The Hackitt review has also called for a clearer, statutory change control process – one that places requirements on the relevant dutyholder to notify the regulators of substantial changes after full plans sign-off. Within that context, two types of changes should be defined, it adds – ‘major’ and ‘minor’. “Major changes would be a limited list of significant changes; for example (a) changes in use, number of storeys or number of units; or (b) changes which could impact on previously signed-off building safety plans.” Major changes would require an update from the dutyholder to the joint competent authority, for reconsideration, before such work starts. Minor changes (that is, all other changes) would need to be recorded and identifiable at the completion of the work for dutyholders to demonstrate that Building Regulations are still satisfied.
This is particularly noteworthy, given that there have been suggestions that ‘flawed alterations’ post-construction played a significant part in the Grenfell Tower disaster, with the original fire safety defences weakened by these modifications. According to a Leader in the Institution of Occupational Safety and Health’s (IOSH) own magazine (https://is.gd/femani), while “the building’s concrete frame and block infill had contained domestic fires to the flats” for the previous four decades…. “the rainscreen cladding panels and architectural crown feature fixed to it in 2015 added both fuel and a conduit for fire to race vertically and horizontally over the facades”, it claims.
Golden thread principles
While the government has already responded favourably to the suggestions raised in the Hackitt report, what will it all mean in practice, if the ‘golden thread’ principle is to be enforced? First, it’s worth examining just how fires spread and how buildings can stop that from happening.
Fire separation between flats and common areas is vital, and achieved by making each flat a fire-resisting enclosure – that is, compartmentalisation – through the construction of bulkheads and sealing penetrations, for example, so as to resist the passage of fire for a specified period of time. Normally, a fire will then burn itself out before it can spread to other parts of the building.
Another common means of a fire spreading is through ‘autoexposure’, a term not often used in the UK. It was coined by a former US fire brigade chief Vincent Dunn, who defined this as “the spread of flames from one floor to the floor above on the outside of the building”. It is now more broadly used to describe any external vertical fire spread. This is effected by an opening, either existing or created by structural failure, allowing heat and flames to exhaust out of the building and impinge on other parts of the building, usually above.
Also becoming more of an issue is external spread through cladding and insulation products. A common practice in the UK when refurbishing high-rise buildings is to clad their exterior with polystyrene insulation sheets, which are at least four inches thick, covered with mesh and rendered. This gives them compliance with Class 1 Surface Spread of Flame and a low fire propagation to BS 476 Part 6 1989. Unfortunately, once this thin render coat fails or is disrupted, it exposes vast quantities of flammable polystyrene.
Installation of these insulation systems is a highly skilled process that requires fire breaks through the wall surface. Guidance (UK, Approved Document B and BS8414) generalises that the insulation material should be of “limited combustion” and that the cladding system will not permit excessive spread outside the building. However, there are already instances in the UK where fire has travelled up the outside of a high-rise building via a clad insulation system. In one case, in Glasgow, in 2009, it travelled nine storeys.
The Local Government Association (LGA) has called on the government to give social housing providers clear guidance on what materials can be used to replace unsafe aluminium composite material (ACM) cladding that was so devastating in the Grenfell fire. “Any revisions of the fire safety guidance on how to comply with the building regulations [Approved Document B] should make it clear that all the material in cladding systems used on buildings over 18 metres in height should be of limited combustibility or have passed a robust full-scale fire safety test,” says the LGA. “It should also be clear that desktop studies are not acceptable as evidence of compliance with Building Regulations.”
Planning for fire protection should involve an integrated approach in which system designers analyse building components as a total package (that is, how they all work together), mostly going beyond basic code compliance and the owner’s minimum legal responsibilities for providing protection. From the outset, building ownership and management, architects, engineers, contractors and consultants all need to be involved in the planning and design process, and fully understand the issues and concerns of all other parties. This is a highly intricate process, however, and often subject to and influenced by the diverse responsibilities and interests of those directly involved.
In the face of such potential obstacles, it is little wonder that Gary Strong, the RICS global building standards director, points to the Grenfell Tower fire as clearly demonstrating the need for a coherent global approach to fire safety in general. As the RICS representative to, and chair of, the International Fire Safety Standards (IFSS) Coalition, he says that the Grenfell fire not only focused attention on building and fire safety in the UK, but also exposed global inadequacies in how fire safety standards are set. As its first order of business, the IFSS Coalition is organising a review of high-level standards.
According to Strong, fire risk assessments for existing buildings have become imperative in the wake of Grenfell and the Hackitt report. “RICS recommends a holistic approach be taken to the whole building and not just the cladding in isolation. The professional that is appointed should carry out a thorough fire risk assessment of the whole fire-related standards of the building, including compartmentalisation, fire prevention/suppression, adequacy of fire escapes/means of escape, means of detection and warning, as well as the cladding and its construction. The building management process, testing regime for gas, electrics and general housekeeping, and the evacuation policy should also be included.”
The risk assessment should include an assessment of the fire spread and the likelihood of any external fire spread reentering the building, thereby creating a “leapfrog effect”, particularly with full-height or near full-height glazing.
“It should be remembered that any fire risk assessor must be suitably experienced and qualified, and anyone advising in these matters must not stray outside their own area of expertise. With regards to the decision regarding removal and replacement of any cladding, that will need to be decided based upon the results of the risk assessment, the on-site survey and testing of the cladding and the insulation behind it,” adds Strong. And, he continues, in consultation with Building Control.
Dealing with external cladding
The construction that is behind the cladding will need to be assessed also – in particular, the fire-stopping cavity barriers and fixings. A sample of the cladding should be removed, in order to identify whether the fire stopping has been adequately constructed and the fixings are non-combustible. “If the sample shows that there is a deficiency, then more should be removed to assess the extent of the deficiency.” (In May, the Fire Protection Association published a critical study of cladding fire safety and the BS 8414 standard: https://is.gd/ucozal)
If the cladding on the building fails the BS 8414 test, then the owner should seek professional advice as to what to do next, which would include removal of the cladding and insulation, and reinstatement with a cladding system which does comply with the building regulations, he adds. “Whilst the government consultation on combustible cladding is underway, and therefore as it is impossible to predict what changes may be made to the building regulations, RICS recommends that any replacement cladding and insulation is fully non-combustible, with well-designed fire stops and cavity barriers, good detailing at junctions with windows and doors, and fireproof fixings used.”
In assessing the safety of the cladding system, it may be necessary to remove isolated panels, either to reveal the construction build-up, or for testing purposes, he points out. “In doing so, care should be taken not to create conditions which may worsen the integrity of the cladding system. This could include exposing insulation or other materials to rain which can affect structural integrity and water tightness, or leaving material exposed which could reduce fire performance and be exposed to wind damage.”
Where sample panels are removed, they should be replaced immediately with a suitable material which ensures continued compliance with all the applicable Parts of Schedule 1 to the Building Regulations including Approved Document B guidance. Responsible building owners must be advised of the risks of just removing sample panels and leaving them off for any period of time.
Strong offers some important caveats. “Replacement cladding may be heavier than the existing system. Cladding panels or insulation materials may have a lower resistance to fixings pulling through than the original panels. For example, replacement insulation may be heavier, particularly if it can absorb water – for example, from rain during installation or rain penetration through the outer cladding. In addition, removal of the original panels may damage fixings, the fixing system or the building substrate.”
If fixings, or a fixing system, is to be reused, the original design and suitability for the new application should be checked. He concludes: “This should also include a structural engineers’ assessment of resistance to wind loads. It should not be assumed that the original specification of fixings was adequate, as there is always a risk that the original system was not designed or installed correctly. RICS is aware of anecdotal evidence of inappropriate plastic fixings having been used, and these must be removed and replaced with fireproof fixings. All fixings should take account of the condition of the building substrate and performance in a fire.”
BOX OUT 1: Complexities around fire containment
Steve Skarratt, head of prevention and protection training at The Fire Service College, points to the many complexities that exist around effective containment of fires in high-rise buildings, not least poor management and poor design. He says: “This impacts on how you pre-empt fire in the first place. If a fire does break out, how do you protect people and buildings, so that fire doesn’t spread? Both instances require the highest levels of building design and risk assessment in the first place. The challenge here is that there are often so many, often conflicting, views as to what this constitutes, often without full knowledge and/or engaging with others involved in the process – designers, architects, engineers, consultants, for example. It’s a highly tangled web.”
The Fire Service College now runs a course, ‘Fire Safety Engineering Principles’, that serves as an introduction to the alternative methods to any prescriptive guidance on building design. It offers guidance to, and interpretation of, the BS7974 series (which provides a framework for an engineering approach to achieving fire safety in buildings). More information: https://is.gd/ohapes
BOX OUT 2: Competency standards
In response to the Hackitt Inquiry, the Institution of Fire Engineers is working with other organisations to develop competence frameworks for fire engineers: https://is.gd/ubexav
Competency standards for fire risk assessorshave been published by the Fire Protection Association: https://is.gd/oyekep and https://is.gd/wonebo