Setting the stage: the evolution of fire-door core materials
The long-standing practice of using chipboard core in timber fire doorsets, primarily for its cost-effectiveness and fire-performance properties, now faces a pressing need for reassessment. The impact of natural and built environment elements on these doorsets underscores the necessity to evolve and enhance safety standards.
What is chipboard? Chipboard is an engineered wood product made from wood chips, resin and adhesive as a bonding agent. It is commonly used as the core material in ‘timber fire doorsets. It is typically covered with a layer of wood or other fire-resistant materials to help the door withstand fire for specified durations, ranging from 30 to 90 minutes and occasionally up to 120 minutes. The primary purpose of these doorsets is to prevent the spread of flames and smoke during a fire.
Introduced in the 1940s and 1950s as a cheaper alternative to solid wood and plywood, chipboard offered improved quality and better fire-resistance properties than the former, making it a popular choice in the door-manufacturing industry. Later, for the fire-resistance test of wooden door assemblies, the market and core manufacturers established a trend based on various historical tests: using a 44mm core for 30 minutes of fire resistance, a 54mm core for 60 minutes and a 64mm core for a 90-minute rating.
Weighing the pros and cons of fire-door core materials
While chipboard offers several advantages, it also has significant drawbacks. It is susceptible to swelling and deterioration when exposed to humidity and moisture, compromising its structural integrity and fire-resistance capabilities. Furthermore, chipboards are generally less durable than solid wood, mineral-based cores, or metal doors, limiting their use in high-security areas. Some resins and chemicals used in its production can also adversely affect the environment. However, due to increased market competition, the density of chipboard cores has drastically reduced over the years, falling from around 550–575kg/m³ to more or less 100kg/m³. This reduction has made it challenging for the cores to withstand the necessary pressure and temperature during fire tests. It is now essential for the industry to either improve the density and overall performance of the cores or to adopt new technological advancements, such as applying a fire-retardant coating on the chipboard, to enhance its fire resistance.
Critical considerations for fire-door materials in the Middle East
With its changing weather patterns and increased humidity, the Middle East presents a unique challenge for chipboard. The region’s susceptibility to sudden and rapid extreme weather conditions further exacerbates the risk of damage due to moisture.
The use of chipboards in timber fire doorsets continues to evolve with advancements in material science and fire-safety technology, adapting to the needs of various global markets, including the Middle East. However, the growing number of regional chipboard suppliers is a cause for concern. Many of these core manufacturers produce the core elsewhere and may not adhere to local regulatory requirements, posing a potential risk.
Overview of key fire testing standards for door assemblies
In the Middle East, two standards are widely recognised for fire testing timber fire doorsets with chipboard cores. They are BS 476-22 and EN 1634-1. However, some door manufacturers (joineries) often use particular core brands to pass the fire test but then use multiple, sometimes unbranded and untested, cores for their projects. This practice can compromise the fire safety of the doorset and leads to catastrophe.
Effective strategies for minimising fire risks in door assemblies
To address these issues, I have listed several measures that can be implemented:
- Core manufacturer accountability: Core suppliers/manufacturers should create awareness about identifying their products on social media and websites. They should apply markings on all four sides of the fire core, including the brand name, model, thickness, batch number and origin. It’s challenging to imprint it on chipboard, but this information aids door manufacturers and certification bodies (CB) to ensure traceability and authenticity.
- Certification body vigilance: CBs play a crucial role in ensuring the safety of fire doorsets. They should ensure that joineries conduct proper incoming inspections of all batches of fire cores received in their factories. Photographic evidence and inspection reports should be maintained for traceability for all batches. Initial audits from CB should verify that joineries have qualified inspectors and stringent inspection systems.
- Joineries’ role: When the door manufacturer requests the CB for fire labels, they should include the core supplier/manufacturer in the email loop. This ensures the core manufacturer knows the labels are being procured for a supplied material and that their core will be utilised in the project.
- Supplier monitoring: Core suppliers/manufacturers should monitor the joineries they work with. Any suspicious activities should be reported in writing to the respective CB. The certificate will be temporarily put on hold until the issue is resolved. If found guilty, the matter should be escalated to the authorities having Jurisdiction (AHJ) or project consultant for further action.
- Regular testing: CBs should conduct periodic tests of the fire cores, especially when suspicious activities are detected, to ensure ongoing compliance with safety standards.
By implementing these measures, the Middle East market can ensure the safety and reliability of timber fire doorsets, safeguarding lives and property.
Moving from chipboard to mineral-based composite fire cores in the door industry
As concerns over chipboard grow, the door industry must advance by adopting mineral-based composite fire cores. These cores offer significant benefits over traditional chipboard, including enhanced durability and strength.
Advantages of mineral-based composite fire cores in modern fire-door design
Mineral-based composite fire cores comprise calcium silicate, vermiculite, fibre cement boards, Tectonite, etc. These ingredients contribute to the core’s superior fire resistance, making it a more reliable choice for fire-rated doors. The key benefits of mineral-based composite cores include:
- Enhanced fire resistance: Mineral-based cores can withstand higher temperatures and more prolonged exposure to fire compared to chipboard. This is due to the inherent properties of the minerals used, which do not ignite or degrade quickly under high heat.
- Durability and longevity: These cores are less prone to warping, swelling or degradation over time, guaranteeing that doors maintain their structural integrity and fire-resistance properties throughout their lifespan. They are also more durable and resistant to moisture, pests and other environmental factors that can degrade the door over time.
- Strength and stability: Mineral-based core materials provide greater strength and stability, making the doors more resistant to impact and wear.
- Improved sound insulation: Mineral-based composite fire cores provide better sound insulation due to their density and composition. These cores achieve an acoustic rating of up to 40–44dB or more, making them suitable for applications where noise reduction is crucial, such as in commercial buildings, hospitals and educational institutions.
- Holding power: Screws have excellent holding power in mineral-based composite cores due to the density and stability of the material. This ensures a secure attachment that is less likely to loosen over time.
- Advantage to specifications and dimensions: One of the most significant advantages of mineral-based composite fire cores is their optimised thickness. It can achieve higher fire-resistance ratings with thinner profiles than chipboard cores. For example:
- 45mm core provides a 60-minute fire-resistance rating.
- 50mm core provides a 90-minute fire-resistance rating.
- 55mm core provides a 120-minute fire-resistance rating.
Comparison with chipboard: In contrast, chipboard fire doors require thicker cores to achieve similar fire-resistance ratings:
- 54mm core for a 60-minute fire-resistance rating.
- 64mm core for a 90-minute fire-resistance rating.
- 64–70mm core for a 120-minute fire-resistance rating.
This difference in thickness means mineral core doors can be more versatile and suitable for a broader range of architectural and design applications where space and aesthetics are essential.
Expanding applications of mineral-based fire cores across global standards
Historically, mineral-based composite fire cores were primarily used for doorsets requiring compliance with American standards (UL 10C), which involve rigorous testing methods such as fire endurance and hose stream tests. However, given the increasing concerns over the limitations of chipboard, mineral-based cores are now considered a viable option for doors tested to British (BS) and European (EN) standards.
Essential fire testing requirements for compliance and safety
For doors tested to EN standards (EN 1634-1), it is essential to note that the standard does not define a weaker side for composite-based (mineral-based) fire doors, as outlined in Annex C of EN 1634-1. Consequently, bi-directional testing is mandatory for asymmetrical door assemblies to ensure their effectiveness against fire from both sides.
Due to the lack of sufficient evidence regarding the behaviour of inorganic-based doorsets (e.g. calcium silicate, vermiculite, fibre cement boards) and plastics-based doorsets (e.g. glass-reinforced polyester, PVC) in fire, asymmetrical test specimens must constantly be tested from both sides. This requires a minimum of two test specimens to confirm their performance under fire conditions
Embracing the future of fire-door technology
As the fire-door industry advances, there is a marked shift towards adopting mineral-based composite fire cores over traditional chipboard cores in timber door assemblies. The need for enhanced safety, durability and design flexibility drives this transition. Mineral-based cores offer superior fire resistance and ensure better acoustic performance, structural integrity and long-term reliability under challenging environmental conditions. Their ability to maintain door integrity during fire events, thanks to better screw retention, makes them a crucial choice for modern construction projects.
Moreover, with increasingly stringent safety standards and environmental considerations gaining prominence, using mineral cores represents a progressive step forward. These cores provide higher fire ratings with optimised, thinner profiles, catering to safety and aesthetic needs without compromising performance. For designers and project consultants, specifying mineral-based fire doors is not just a trend but a necessary evolution in fire safety, ensuring that buildings are compliant and future-proofed against tomorrow’s demands. This strategic move towards mineral cores solidifies the industry’s commitment to safeguarding lives and properties while adapting to the evolving landscape of safety and sustainability.
For more information please visit https://emirateslaboratory.com/
About the Author
Mohammed Nouman
A TIC Industry professional, Mohammed Nouman is a Senior Certification Specialist with Emirates Safety Laboratory (ESL), specialising in fire-rated door product certification, factory production control auditing, product sampling of wood, steel and glazed fire-rated doors, and conducting in-the-field surveys and inspections for projects, as per NFPA 80, to ensure doors are installed correctly in compliance with the regulations. He supports projects and clients across the Middle East, North Africa and Indian Sub-continent regions for fire-safety products.
