40 Leadenhall, London

This 34-storey, 910,000-squarefoot office hub incorporates state-of-the-art amenities, a heritage restoration, and pioneering environmental technologies.
Working in collaboration with a Proteus Approved Contractor, we supplied and supported the application of advanced, sustainable flat roof and terrace waterproofing solutions across 5,380m² of roof space on the North Tower, South Tower, and the restored Grade II listed 19–21 Billiter Street.

Challenges and Considerations
Conventional office buildings often fall short in delivering environmental benefits and occupant well-being. With a focus on reversing this trend, the developers of 40 Leadenhall engaged Proteus Waterproofing at the early design stage to integrate eco-conscious waterproofing and insulation systems. The objective was clear: exceed thermal performance standards, eliminate environmental compromise, and deliver robust green roofing solutions across a structurally and logistically complex site.Multiple roof levels, a large footprint, and an extensive number of terraces presented considerable technical and logistical hurdles. These included:
• Significant variation in terrace layouts and roofing zones.
• Need for phased installation with constant area transitions.
• Strict environmental, safety and scheduling requirements in a densely developed part of the City.

Delivery and Collaboration
From the onset, Proteus Waterproofing and the Approved Contractor worked in lockstep, with Proteus’ in-house Technical Design Team conducting detailed U-value calculations to meet thermal requirements. Coordination was essential throughout the project due to the varying sequence of works, complex logistics, and high-rise installation challenges.To maintain quality assurance and project momentum, regular site visits were conducted. The Proteus team provided hands-on guidance, technical support, and photographic documentation of all key installation phases, ensuring that every aspect of the waterproofing was implemented to the highest standard.

Sustainable Impact
Green roofs installed across 40 Leadenhall’s terraces provide a wide range of long-term benefits:
• Thermal Regulation: Enhanced energy performance and reduced urban heat island effect.
• Biodiversity: Support for pollinators and urban wildlife.
• Stormwater Management: Natural water retention and drainage delay.
• Air Quality Improvement: Reduction in airborne pollutants.
In line with our company ethos, sustainable supply chain practices were also embedded into the delivery process, from material forecasting to ethical sourcing and on-time logistics.

Outcome
The collaborative approach between Proteus Waterproofing, the Approved Contractor, and all other stakeholders ensured the waterproofing works met the project’s exceptional design, environmental, and performance standards.This landmark project has since been honoured with prestigious accolades including:
• Building Innovation Award – Most Innovative Commercial Project
• The Architects Company Award – City of London Building of the Year 2024

Conclusion
40 Leadenhall is more than a commercial development – it’s a sustainable blueprint for the modern workspace. From heritage integration to environmental excellence, this project showcases how innovative waterproofing and insulation systems can contribute significantly to building longevity, occupant wellbeing, and environmental stewardship.
Proteus Waterproofing is proud to have played a part in shaping this iconic London skyline, delivering a waterproofing solution that is as future-facing as the building itself.