2 Aldermanbury Square
Aldermanbury Square
Client: Great Portland Estates (GPE)
Main Contractor: Keltbray (Demolition and Substructure) / Lendlease (Superstructure)
Great Portland Estates' 2 Aldermanbury Square transforms an ageing commercial tower into London's showcase for circular economy construction. The existing building on the site consisted of a late 1980s steel-framed structure comprising 9 levels above ground and 2 basement levels. Following the demolition works, Keltbray constructed a new basement box and 12-storey core for the new building. All works were carried out on a constrained urban site surrounded by heritage structures and operational utilities.
Wentworth provided construction engineering and temporary works design from pre-demolition through basement completion, developing methodologies that enabled Keltbray to safely deconstruct, reuse existing materials, and construct the new basement while protecting sensitive neighbouring assets.
Wentworth provided construction engineering and temporary works design from pre-demolition through basement completion, developing methodologies that enabled Keltbray to safely deconstruct, reuse existing materials, and construct the new basement while protecting sensitive neighbouring assets.
300k
kgCO2e saved by designing with reclaimed steel compared to specifying new sections.
1,800
tonnes of structural steel salvaged and reused
40
temporary works schemes designed by Wentworth
Our Role
Our RoleWentworth’s engineers attended site regularly working alongside Keltbray's construction team throughout the demolition and substructure phases of 2 Aldermanbury Square. Our role was to be agile, evolving the construction methodologies and temporary works designs as site conditions revealed themselves.
Our scope saw us design over 40 temporary works schemes, including demolition sequencing, retaining wall assessment, basement propping systems, tower crane bases, core stability, and logistics gantries.
We worked with the permanent works engineer, Arup, to maximise material reuse and minimise carbon emissions on the project.
Our scope saw us design over 40 temporary works schemes, including demolition sequencing, retaining wall assessment, basement propping systems, tower crane bases, core stability, and logistics gantries.
We worked with the permanent works engineer, Arup, to maximise material reuse and minimise carbon emissions on the project.
Capabilities
Capabilities- Buildings
- Substructure
- Hydraulic Jacking
- Demolition
- Structural Engineering
- Geotechnics
- Construction Method Engineering
- Temporary Works
- 3D Modelling
- Social Value and Sustainability,
- Wentworth Labs
Salvaging 1,800 tonnes of undamaged steel frame
Salvaging 1,800 tonnes of undamaged steel frameThe existing City Place House steel frame offered major carbon savings through reuse if salvaged intact. Wentworth worked alongside Arup to minimise carbon emissions associated with the project by maximising the re-use of the existing structure’s materials. A key achievement for the project was the ability to salvage 1800 tonnes of the existing steel frame for reuse rather than recycling. The client had designed a new structure within London which reused the salvaged steel within its primary frame, with some steel also reused on the new 2 Aldermanbury Square structure.
This project showcased engineering excellence through the meticulous dismantling and reuse of existing steel structures. All steel members were assessed, sized for reuse, and stored safely awaiting transport for processing.
The floor plates had limited capacity for demolition plant, so the deconstruction sequence had to avoid overloading neighbouring structures while maintaining safe working platforms. We worked closely with Keltbray to map member sizes, assess floor plate capacities, and determine which demolition plant could safely operate at each level.
This project showcased engineering excellence through the meticulous dismantling and reuse of existing steel structures. All steel members were assessed, sized for reuse, and stored safely awaiting transport for processing.
The floor plates had limited capacity for demolition plant, so the deconstruction sequence had to avoid overloading neighbouring structures while maintaining safe working platforms. We worked closely with Keltbray to map member sizes, assess floor plate capacities, and determine which demolition plant could safely operate at each level.
Assessing existing basement wall movement limits
Assessing existing basement wall movement limitsThe new basement at 2 Aldermanbury Square extended 12 metres deep, significantly deeper than the original. But the heritage structures and utilities immediately adjacent to the site imposed stringent movement limits on the existing piled basement walls. We had to verify whether these walls could safely retain the deeper excavation without exceeding deflection criteria that would damage sensitive neighbouring assets.
Wentworth undertook detailed geotechnical analysis of the existing retaining walls, modelling their behaviour under the proposed increased lateral loads from 12 metres of excavation depth. Our finite element analysis determined the walls' capacity and predicted deflections, then we designed verification monitoring protocols to track actual performance against our predictions.
Wentworth undertook detailed geotechnical analysis of the existing retaining walls, modelling their behaviour under the proposed increased lateral loads from 12 metres of excavation depth. Our finite element analysis determined the walls' capacity and predicted deflections, then we designed verification monitoring protocols to track actual performance against our predictions.
Designing multi-phased basement propping scheme
Designing multi-phased basement propping schemeCreating the new two-storey basement involved demolishing the existing basement raft while maintaining retaining wall stability, cross-site load balance, and access for heavy demolition plant. This was all coordinated through a complex sequence of prop installation and removal. The added challenge was that the entire 180-tonne propping system was designed using reclaimed steel.
We developed a carefully sequenced programme of jacked steel Circular Hollow Section (CHS) prop installation that maintained wall stability throughout. This enabled Keltbray to demolish the existing basement raft in phases and excavate down to formation level.
Our 3D modelling coordinated prop positions with demolition plant access requirements and new Reinforced Concrete (RC) box construction, ensuring props could be removed safely as permanent works progressed. By designing around the existing reclaimed steel stock specifications rather than ideal new sections, we accommodated material reuse throughout.
This phased propping approach kept the retaining walls stable throughout excavation, maintained cross-site load distribution, and provided clear access for 360-degree excavators breaking out the existing raft. Designing for reclaimed steel saved over 300,000 kgCO2e compared to specifying new sections.
We developed a carefully sequenced programme of jacked steel Circular Hollow Section (CHS) prop installation that maintained wall stability throughout. This enabled Keltbray to demolish the existing basement raft in phases and excavate down to formation level.
Our 3D modelling coordinated prop positions with demolition plant access requirements and new Reinforced Concrete (RC) box construction, ensuring props could be removed safely as permanent works progressed. By designing around the existing reclaimed steel stock specifications rather than ideal new sections, we accommodated material reuse throughout.
This phased propping approach kept the retaining walls stable throughout excavation, maintained cross-site load distribution, and provided clear access for 360-degree excavators breaking out the existing raft. Designing for reclaimed steel saved over 300,000 kgCO2e compared to specifying new sections.
Coordinating 40 complex temporary works schemes
Coordinating 40 complex temporary works schemesBeyond the major demolition, geotechnical, and propping elements, the confined nature of this urban site meant we had to design dozens of interconnected temporary works solutions. Each temporary works design accommodated the others while maintaining safety, access, and the programme. Tower crane bases, back-propping during core construction, cantilevering scaffold supports, and logistics gantries all competed for limited space and needed coordinated installation sequences.
Our engineer worked with Keltbray's site operations, designing temporary works that evolved with site conditions. We coordinated sequences that allowed crane bases to support demolition, then core construction, then steel erection. Meanwhile, back-propping maintained structural stability, scaffolds provided safe access, and logistics gantries enabled material deliveries, all within a continuously changing site.
This integrated approach to 40+ temporary works schemes prevented conflicts, maintained programme, and gave Keltbray the confidence to execute complex operations safely. Our temporary works engineer was on hand to respond immediately when site conditions changed, redesigning solutions without delaying construction.
Our engineer worked with Keltbray's site operations, designing temporary works that evolved with site conditions. We coordinated sequences that allowed crane bases to support demolition, then core construction, then steel erection. Meanwhile, back-propping maintained structural stability, scaffolds provided safe access, and logistics gantries enabled material deliveries, all within a continuously changing site.
This integrated approach to 40+ temporary works schemes prevented conflicts, maintained programme, and gave Keltbray the confidence to execute complex operations safely. Our temporary works engineer was on hand to respond immediately when site conditions changed, redesigning solutions without delaying construction.
Outcomes
OutcomesKey results:
Aldermanbury Square is now targeting net zero carbon and WELL Gold certification.
- Circular economy delivered: 1,500 tonnes of structural steel salvaged and reused without damage
- Carbon savings quantified: Over 300,000 kgCO2e saved through reclaimed steel propping design
- Heritage protection: Existing basement walls reused for deeper excavation without exceeding tight deflection criteria
- Design integration: 40+ temporary works schemes coordinated through multi-phase construction without conflicts or delays
- Value of early involvement: Construction methodology evolved with site conditions through continuous collaboration
Aldermanbury Square is now targeting net zero carbon and WELL Gold certification.
“We are immensely proud of the engineering expertise we brought to the project, and the collaborative approach between Wentworth, Arup and Keltbray, to realise the client GPE’s challenging vision of delivering a building that goes beyond embodied carbon norms for a new build development by integrating principles of circular economy.”
John Hodge
Lead Temporary Works Engineer
Wentworth