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Overview
Heathrow Airport Terminal 4 is one of the key passenger terminals within the Heathrow Airport complex, handling a high volume of international departures each year. The terminal building includes a long series of rooflights positioned above the check-in desks and security areas within the International Departure Lounge.
Originally installed in 1981, the existing rooflight system had reached the end of its operational life. After decades of exposure to environmental conditions and the continuous demands of a busy airport terminal, the glazing required replacement to ensure continued performance, safety, and maintainability.
The challenge was not simply replacing a rooflight system. Any upgrade needed to meet modern performance standards while working within the structural constraints of the existing terminal building. Additionally, Heathrow Airport has strict operational and security requirements, meaning that refurbishment work must be carefully planned to minimise disruption to passengers and airport operations.
Structura was appointed to deliver the rooflight replacement works, providing specialist façade engineering expertise and installation of a modern Kalwall Skyroof system across the length of the terminal rooflight structure.
The completed project delivered a durable, high-performance rooflight system that allows natural light to flood into the terminal space while improving long-term maintenance accessibility and ensuring compliance with modern safety standards.
Details
Location:
Heathrow Airport Terminal 4, London
Architect:
Pascall + Watson Architects
Main Contractor:
Balfour Beatty
Grid:
Shoji
Project Metrics
Key performance and project metrics include:
Rooflight system installed: Kalwall Skyroof
Total rooflight area installed: Over 1,750 m²
Original rooflight installation: 1981
Structural integration: Existing curtain wall framework retained
Installation environment: Live airport terminal above check-in and security areas
Maintenance improvement: Walk-on rooflight surface for future access
The Challenge
Upgrading glazing and rooflight systems within a major international airport presents a unique set of technical and operational challenges. Heathrow Terminal 4 operates continuously, with thousands of passengers moving through the terminal each day. Any construction or refurbishment work must therefore be carefully coordinated to avoid disruption to essential airport functions. For the Terminal 4 rooflight replacement project, several key challenges needed to be addressed.
Ageing Rooflight System
The original rooflight glazing installed in 1981 had reached the end of its lifecycle. Over time, building components exposed to weather conditions can degrade, affecting both performance and maintenance requirements. A modern replacement system was required to ensure the terminal building continued to perform reliably while improving durability and long-term serviceability. However, replacing rooflights within an operational airport building is far more complex than a standard building refurbishment. The work had to be carefully engineered to integrate with the existing terminal structure.
Retaining the Existing Curtain Wall Framework
One of the key requirements of the project was that the existing curtain wall framework supporting the rooflights needed to be retained. Removing and replacing the entire structure would have significantly increased the scale of the project and potentially caused major disruption to the terminal building. Instead, the replacement rooflight system needed to be engineered so that it could integrate with the existing framework, allowing the project to be completed efficiently while maintaining structural compatibility. This requirement demanded precise engineering coordination and careful installation planning.
Meeting Airport Safety & Blast Performance Standards
Airport buildings must comply with strict safety and security standards, including requirements related to structural resilience and blast performance. The new rooflight system therefore needed to meet ASAID compliance standards, ensuring that the materials used provided the necessary level of blast resistance for an airport environment. Meeting these safety requirements while also integrating with the existing structural framework required careful selection of materials and system design.
Working Within a Live Airport Environment
Unlike many construction projects, Heathrow Airport cannot pause its daily operations while refurbishment work takes place. The rooflight replacement works were positioned above critical areas of the terminal, including check-in desks, security checkpoints, and the international departure lounge. Because of this, the project had to be carefully scheduled to ensure passenger flow and airport operations continued without interruption. All installation activities therefore needed to take place within controlled working hours and under strict safety protocols.
Structura’s Solution
To address the complex technical and operational requirements of the Heathrow Terminal 4 refurbishment project, Structura delivered a carefully engineered rooflight replacement solution using the Kalwall Skyroof system. The project required close coordination between façade engineers, contractors, and airport stakeholders to ensure the work was delivered safely and efficiently.
Kalwall Skyroof System Installation
The solution centred on the installation of over 1,750 square metres of Kalwall Skyroof system, a high-performance translucent roofing system designed to provide natural daylight while delivering durability and structural performance. Kalwall systems are widely used in large commercial and transportation buildings because they provide consistent natural light distribution while maintaining structural integrity.
For Terminal 4, the Kalwall Skyroof system was installed across the full length of the existing rooflight structure above the terminal’s check-in and security areas. The system allows natural light to penetrate the terminal interior, improving the passenger environment while maintaining the architectural intent of the original building design.
Integration With Existing Structural Framework
Rather than replacing the entire curtain wall support structure, the Kalwall system was engineered to utilise the existing curtain wall framework as its structural support. This approach offered several important advantages. First, it significantly reduced the scale of the refurbishment works required within the terminal building. Second, it allowed the installation to be completed more efficiently, reducing the amount of time construction teams needed to operate within the live airport environment.
Finally, retaining the existing structure ensured that the overall architectural design of the terminal roof remained consistent with the original building configuration. Careful engineering assessment ensured that the new rooflight system could safely integrate with the existing framework while delivering improved long-term performance.
Controlled Installation Within Engineering Hours
Because the works were located above active passenger areas, all installation activities were carried out within designated engineering hours. This approach allowed the project team to complete the works with minimal disruption to passengers and airport staff.
By coordinating installation schedules with airport operations, the project was delivered safely while maintaining the normal flow of passengers through the terminal. The careful planning and sequencing of installation activities were essential to the success of the project.
Project Results
The Heathrow Airport Terminal 4 rooflight replacement project successfully modernised the glazing system while maintaining the operational continuity of the terminal building. The completed installation delivers several long-term benefits for both the airport and the passengers using the terminal.
Improved Daylighting Across the Terminal
One of the most visible outcomes of the project is the improved natural lighting within the terminal building. The Kalwall Skyroof system allows daylight to spread evenly throughout the interior space, helping create a brighter and more welcoming environment for passengers moving through the check-in and security areas. Natural light plays an important role in improving the overall passenger experience within airport terminals.
Long-Term Maintenance Accessibility
The new rooflight system is now classified as walk-on, meaning it can safely support maintenance access. This significantly simplifies future inspection and maintenance work, allowing airport facilities teams to access the rooflight area without complex temporary access systems. Improved accessibility helps reduce long-term maintenance costs and allows airport staff to maintain the rooflight system more efficiently.
Structural & Safety Compliance
The installation of the ASAID-compliant Kalwall system ensures that the rooflight structure meets modern safety standards for airport buildings. This provides long-term confidence in the durability and resilience of the rooflight system within a high-security environment.
Minimal Operational Disruption
One of the most significant achievements of the project was completing the rooflight replacement works while maintaining full operation of Heathrow Terminal 4. By carefully coordinating installation activities within engineering hours and integrating the new system with the existing curtain wall framework, Structura was able to deliver the refurbishment with minimal impact on passengers and airport operations.
Industry Recognition
The successful delivery of the Heathrow Terminal 4 project also received industry recognition. Following completion of the works, Structura was awarded “Most Promising New Supplier” by Balfour Beatty and “Safety Award” at the Heathrow Supply Chain Event 2019. These awards highlight the quality of the engineering work delivered and the importance placed on safety throughout the project.