Drawing from extensive expertise in façade assessment and inspections, there is a need to understand the paramount significance of perimeter firestops as a critical element of fire containment.
Perimeter firestops act as a barrier to prevent flames from entering a room above via the void created at the intersection of a floor slab and the interior face of the exterior wall assembly. This crucial aspect of fire containment is often overlooked but remains essential in mitigating the rapid spread of fires within a building.
International codes such as the International Building Code (IBC) comprise specific requirements for perimeter fire stops. In India, the Fire Safety Sectional Committee took a serious interest in this particular building element and issued IS 18190: 2023 Fire Resistance of Perimeter Fire Barrier Joint System — Method of Tests which signifies the importance of this test as a full assembly.
Throughout various project phases, the following processes should be addressed, encompassing design considerations, certification and testing procedures, as well as installation and inspection processes. There are several overarching procedures these systems can undertake to ensure compliance and increase building safety, spanning from manufacturing to meticulous installation:
System design:
Designing the perimeter fire barrier involves creating an integrated system placed in the void between the interior surface of the external façade or curtain wall spandrel, and the slab edge or floor assembly. This system primarily comprises two elements: a firestop material and a smoke barrier. Despite its apparent simplicity, ensuring effective design involves critical steps in integrating these longitudinal joints with the curtain wall and the slab sides. Below are crucial considerations to account for when crafting such systems.
The initial aspect pertains to the design of the curtain wall spandrel and its interaction with the system. Spandrels, part of the curtain wall, conceal slab elements such as bracket fixations and floor-to-floor separations. Various codes mandate specific spandrel heights and fire ratings. The composition of spandrels— whether back pans, insulation boards, or other materials—significantly influences the overall performance of the containment system. These elements constitute the system’s outer side and must be accurately represented in a test assembly to ensure seamless integration and continuous support for the firestop system during testing.
On the opposite side of the system attachment lies the concrete slab or floor assembly. Considerations include the fixation method, spacing between supports, primer application, and the design of the smoke seal.
Another crucial factor in the design of the perimeter fire barrier is the joint width and tolerance. Each system has a specified maximum gap allowance. Construction sites involve multiple packages managed by different parties, resulting in built elements possessing allowable deviations in alignment, known as tolerances. While slab edges may have tolerances of ±25mm, external façade systems often adhere to a tolerance of ±3mm. A successful firestop system must flexibly accommodate such tolerances while functioning optimally.
The joint movement stands as another critical consideration. External façades and curtain walls endure external forces like wind loads and building movements, rendering perimeter gaps between slabs and façades as active joints. Therefore, perimeter fire stops necessitate design considerations that accommodate these cyclic movements effectively throughout the project’s life.
A sample representing the system should be consciously chosen, considering all the aforementioned factors, to demonstrate its performance effectively.
Manufacturing and certification:
The certification process ensures that the materials and components of the system are produced under a quality control framework, ensuring uniformity and consistency in the final product. Within this process, components undergo controlled sampling and subsequent testing using representative assemblies to showcase their capability as a complete system. Following successful test completion, the system attains listing as an assembly in a certification directory. Ongoing surveillance audits are carried out to ensure manufacturing is conducted in a consistent manner. An instance of this is featured on WWW.TBWCERT.COM, showcasing its performance and specifications to assist architects and façade consultants in selecting suitable systems. Ratings enumerated in certificates are derived from test outcomes.
When tested as per ASTM E2307 or its Indian equivalent Standard, IS 18190, the F rating and T rating are critical measurements used to evaluate the performance of perimeter fire stop systems. These ratings assess the system’s ability to resist the passage of flames and limit the transfer of excessive heat during a fire.
These ratings are determined through specific testing procedures outlined in ASTM E2307 or its Indian equivalent Standard, IS 18190. The test involves subjecting the perimeter fire barrier system and the adjacent curtain wall system to fire conditions that simulate a real-world scenario, evaluating its ability to contain flames and restrict heat transmission across the barrier.
Understanding these ratings is crucial for builders, designers, and regulatory authorities to ensure that perimeter firestop systems comply with safety standards. It helps in selecting and installing systems that effectively contain fires, safeguard occupants, and minimise property damage during fire incidents.
Installation: The installation of these systems must adhere to regulations that mandate certified contractors to perform the task. Moreover, prudent companies with certified and listed systems exclusively permit licensed contractors for installation, ensuring they undergo extensive comprehensive training to understand the crucial steps involved in the installation process.
The contractor must closely follow the manufacturer’s guidelines regarding cutting, fitting, compression ratio, anchoring, and maintaining smoke seal integrity. This strict adherence is crucial to have a proper perimeter firestop system at the intersection between the façade and the slab.
Moreover, details specified in the certification report, encompassing the description of curtain wall design, spandrel design, mullion protection cover, as well as dimensions and materials, necessitate thorough scrutiny by the consultant to ensure compliance.
Inspection by a third party:
Inspection by a Third Party accredited to ISO 17020 plays a pivotal role in the procedure. It involves documenting the installation of these pivotal joints and serves as evidence of rigorous quality control throughout all phases. ASTM E 2393, titled “Standard Practice for On-Site Inspection of Installed Fire Resistive Joint Systems and Perimeter Fire Barriers,” Scheduling inspections from the onset, considering these hold points are deemed significant in construction, occurring before concealment by finishes.
Every project involves a collaboration among numerous stakeholders. The dedication of all involved parties— including the manufacturer, consultant, contractor, and inspection team—to quality assurance and effective collaboration is pivotal for successful outcomes.
(Co-authored by John Muse and Kevin Zachariah)
