An international perspective on tall buildings
In the early hours of June 14, 2017, 200 firefighters responded to a fire at Grenfell Tower in London. Within 15 minutes, the fire that had started on the fourth floor of the apartment complex had scaled the exterior of the structure, burning through the building’s 24 floors and claiming more than 70 lives. Though there were multiple factors that contributed to the tragedy, the way the fire moved up the exterior building and destroyed so many floors brought international attention to the use and application of combustible cladding.
Beth Tubbs, P.E., FSFPE, senior staff engineer with the International Code Council and board member of the Society of Fire Protection Engineers (SFPE), has spent close to 25 years with the Code Council. As staff lead on the ICC Fire Code Action Committee she works with the membership, including the ICC Major Jurisdiction Committee, on various fire protection and life safety issues. As one of the fire protection engineers with the Code Council, she was tasked with fielding requests following the Grenfell Tower fire, which led a further interest and research into exterior wall finishes and cladding issues. Based on her experience, she was invited to London to present at the Sixth International Tall Buildings Conference.
Hosted annually by the UK-based Tall Buildings Fire Safety Network — dedicated to advancing “the understanding of fire risk management in tall buildings, during design, construction, occupation and firefighting operations” — the International Tall Buildings Conference is attended by a diverse audience of nearly 100 people with discussion on a broad range of topics.
Tubbs’ presentation — “Impact of the Grenfell Fire on the U.S. Building Regulatory System” — specifically addressed the codes and standards related to cladding. “I wanted to tell them about the Code Council and what the it does … most countries do not write and implement codes quite the way we do,” Tubbs explained. “Most countries regulate buildings at a national level, perhaps through a ministry or some other national system that the government is part of. Often, they are not aware of how the U.S. system works. [I wanted to] explain our process — which is fairly unique — compare notes and see where we may share ideas and learn from one another. In some, cases it seems that our systems are quite different but in other ways we encounter similar problems particularly since manufacturing is far more global than ever before.”
Her presentation addressed three key concerns: Can this happen in the U.S.? Do the current technical requirements result in safe buildings? And how are jurisdictions and designers addressing these issues? “What so many hyper-focus on is the cladding itself,” said Tubbs. “The cladding was sort of a symptom of a bigger problem and focusing on the cladding would not be a fair assessment of what happened.” According to Tubbs, the bigger problems are associated with various social issues, other building construction features and the regulatory system.
While first acknowledging that exterior cladding is only part of a system of components that must be in place to ensure fire protection and life safety, Tubbs explained that some of the other components for tall buildings specifically include emergency voice/alarm communication systems; automatic fire sprinklers; multiple interior exit stairways; standby and emergency power; and firefighter elevator controls, fire service access elevators and fire command centers. For all new and modern high rises within the U.S., many of these safety features would be present due to the implementation of the International Building Code (IBC) or legacy building codes.
Exterior wall finishes and cladding must meet the code requirements outlined in Chapter 14 (Exterior Walls) and Chapter 26 of the IBC, which covers the use of foam plastics. There are a variety of requirements related to fire safety in these chapters. These requirements trigger a number of tests for the materials. Of particular note is NFPA 285, Standard Fire Test Method for Evaluation of Fire Propagation Characteristics of Exterior Wall Assemblies Containing Combustible Components. The UK equivalent test is BS 8414, Fire Performance of External Cladding Systems. NFPA 285 is called up for a number of different reasons but primarily where there is a combustible water resistive barrier or combustible materials such as foam plastic insulation, Metal Composite Materials (MCM) or water resistance barriers. These fire propagation tests give a better indication of actual fire performance. Testing is important however the reality is that such testing is very expensive and can delay a project and instead engineering judgement also called “desktop studies” are used in place of testing. A major concern voiced by Tubbs is, “Are people doing the testing they are supposed to be doing?”
The NFPA 285 and BS 8414 standards require that the whole assembly be tested in the configuration in which it is to be utilized and installed. What often happens in practice in the U.S. and the UK — and what happened with the Grenfell Tower — is that the specific wall system is not tested; instead the wall systems are evaluated through what is termed an “engineering judgement” or “desk-top study.” Tubbs’ concerns relate to the level of qualifications by those undertaking such approaches. Measuring qualifications is outside the building code purview and predicting the behavior without testing is difficult. Simply because individual cladding or wall finish components may have passed the fire testing, the wall covering system as it is to be installed was never tested as a complete system. Installation features such as cavity width, insulation, and product brand and type can affect how fire will move and react. Adding another layer of difficulty in the UK is that the level of accreditation and accountability as “qualifications and requirements for different trades and engineers” has not been as strict as within the U.S.
“After Grenfell happened, my biggest concern and the conclusions we were coming to — within the Code Council and the design and regulatory community in the U.S. — was that this was not a technical failure as much as a process failure,” explained Tubbs. “We need to make sure, from our members’ perspectives, that our designers are clear on the design side of the equation and that the jurisdictions understand what they should be looking for in that design … making sure that what was specified is being put on the building, and that the installation itself meets the designers’ and manufacturers’ requirements as tested.”
In the U.S., the code requirements, material testing and wall details are only part of a system of approvals that provides a level of accountability and redundancy to ensure the safety of buildings and their occupants. Other components include product accreditation and labeling and potentially the use of an ICC-ES report for a specific product approval. The final step is inspections, which may be conducted by a third party and are approved by the authority having jurisdiction. Due to the complicated nature of modern wall systems Tubbs feels that the concept of inspection potentially needs more focus.
Governmental consensus voting recently closed on the Group B public comment hearings; however, the issues related to cladding were addressed primarily in the previous Group A cycle in 2018. These revisions were primarily necessary clarifications. There were exceptions that appeared to allow MCM without fire propagation testing that were misleading as other aspects of the wall system would still require testing to NFPA 285. In Group B, one important change was to the International Existing Building Code (IEBC), which in the 2021 IEBC will specifically link back to the exterior wall requirements in the IBC when renovations occur that involve cladding. This revision was felt necessary as Grenfell Tower also was an existing building. New high-rise buildings in the U.S. have a very rigorous package of requirements that an existing building may not. More care must be taken for those buildings, especially with the rising complications of such wall systems.
As a takeaway for conference attendees, Tubbs explained that the Code Council has been paying attention and attempting to learn in order to contribute to a safer and improved world. The Code Council has partnered with other organizations to promote and drive safety features that will contribute to safe buildings. These organizations include the Inter-jurisdictional Regulatory Collaboration Committee, the International Fire Safety Standards, and the Society of Fire Protection Engineers. These organizations are dedicated to the development and advancement of building fire protection, and the professionals charged with their occupant’s safety. Additionally, the Code Council relies on its membership to be the eyes and ears in the field, and voice concerns and solutions that may arise or be implemented within their respective jurisdictions. Collectively, the work will not only provide for more thorough accountability and approval processes for cladding and exterior wall finish assemblies, but contribute to safer, more resilient communities.