20 Giltspur Street
Saving cost, time and carbon by thinking inside the box.
Despite vertical, horizontal and below-ground constraints, we unlocked a 30% gross area increase and 41% increase in net internal area through the innovative use of floor jacking. By realigning existing floor plates, we unlocked hidden volume and carved out space to construct a whole new floor.
This bold reconfiguration delivers a 30% cost reduction and reduces the programme by 25%. Achieving a 350m3 reduction in demolition by reusing two metal deck slabs, it sets a new benchmark for re-use and postcode-driven circularity.
Currently on site, the 100,000-square-foot redevelopment, backed by clients Norges Bank Investment Management and Simten Developments, has been pre-let to financial services group Octopus.
- Architect
- Buckley Gray Yeoman
- Client
- Simten Developments | Norges Bank Investment Management
- Location
- London, UK
Impact
Through the vertical relocation of two existing floors to accommodate the insertion of a third, we delivered a 40% increase in lettable space while maintaining the external building volume.
Rather than demolish and rebuild, 2,520m² of concrete slab was carefully jacked, repositioned and integrated back into the structure.
With precise BIM coordination and sequencing 240 tonnes of existing steelwork was retained and repositioned, avoiding the emissions and costs associated with fabricating and transporting new materials.
The floor jacking approach proved both leaner and faster than the conventional steel-CLT hybrid scheme. The relocation of slabs, which took just three days, saved £2 million and 25% reduction in programme.
Our jacking solution achieved structural embodied carbon figures (A1-A5) of 127 kgCO₂e/m² (A1–A5) for structural works compared to 251 kgCO₂e/m² using the business-as-usual approach to demolish and rebuild three floors (LVLs 01-03) in new steelwork and metal deck slabs.
Awards
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2025 Construction News Awards – Project of the Year (under £20m)
Context
The existing building, constructed in 1999 for Merrill Lynch as part of Bank of America’s campus, was once home to the largest trading floors in the world. Generous floor to ceiling heights of 5.5m with 1.5 deep service zones were designed for a function that has since moved on.
The site presented a series of fixed constraints. Hard against the St Paul’s Cathedral viewing corridor, upward extension was not possible. Below ground, the building is constructed above a section of the Roman Londinium Wall (a scheduled ancient monument) and multiple rail tunnels. Outward extension was also not an option, as the site is bounded by St Bart’s Hospital, a pub, public realm, and the Bank of America building.
Recognising the opportunity to incorporate an extra floor within the existing massing, we proposed a radical circular solution: to retain and reuse what was already there, and to lift entire floors into new positions.
20 Giltspur Street
Our Approach
Unlocking Hidden Volume
Oversized 5.5 m trading floors, once necessary for the building’s former use, had become wasted space. By reducing floor-to-floor heights to modern standards, we unlocked enough headroom to create an entirely new level through jacking the floors. This reconfiguration increased the lettable area by 40% within the same external mass.
Digital-First Coordination
The complexity of jacking floors demanded unprecedented precision and close collaboration across the design team. From Stage 2 we managed the BIM process, producing the BEP, coordinating survey and design models, and using clash detection to resolve conflicts between new MEP openings and the existing steel frame. This digital-first approach allowed decisions to be made before contractors arrived on site, de-risking the process and ensuring buildability.
Savings in Carbon, Time and Cost
Floor jacking replaced the need for demolition and rebuild, delivering a £2 million saving, a 25% programme reduction, and 49% lower embodied carbon compared to the business-as-usual approach to demolish and rebuild three floors (LVLs 01-03) in new steelwork and metal deck slabs. Proof that the most sustainable solution can also be the best commercial choice.
Engineering Solution
Before any floor movement could take place, the building was digitally modelled and surveyed to fully understand the building and its constraints. Point-cloud surveys by our BIM services team established precise geometry and monitoring control points allowing the jacking sequences to be rehearsed virtually.
The braced core was adapted to maintain stability as the floor levels shifted, and temporary needle beams and hydraulic jacks were carefully installed to support the load transfer. Saw-cutting freed the slabs from their perimeter beams, and new edge beams were introduced to preserve the integrity of the Vierendeel frame.
Once isolated, each 450-tonne slab was lifted incrementally using over 100 hydraulic jacks. Work proceeded floor by floor and was executed in small, controlled stages.
Real-time monitoring showed that corners and transfer beam zones were prone to rising more quickly, so water-filled bowsers and adjustments to jack pressures were introduced. Some jacks carried very little load and were deactivated to ensure uniform movement.
By the end of the jacking process, Level 1 was raised by ~2.3 m and Level 2 by ~1.2 m, creating three evenly spaced floor levels within the original building envelope.
With the slabs in their new positions, the focus turned to making the geometry permanent. New edge beams and connections to the columns were installed, shear connectors and infill toppings were cast to complete composite action, and the core bracing was reconfigured to align with the new floor heights.
Temporary works were sequentially removed, and final as-built surveys confirmed the precise alignment and protection of the Roman Wall and underlying infrastructure.
Quote
“Working with Elliott Wood was absolutely fantastic. From day one, I felt straight away that we had a partner with us who would work with us and help us along the way.”
Construction
The success of the jacking works hinged on close coordination with enabling works contractor Deconstruct. Temporary works, sequencing, digital modelling and real-time monitoring were carefully aligned to ensure each stage was safe, predictable and buildable.
During opening-up works, we identified that the perimeter beams formed part of a Vierendeel frame spanning over below-ground infrastructure, including part of the London Wall. As the stiffness of this frame relied on the integrity of the beam-to-column connections, it was critical that this behaviour was preserved during the jacking process.
To achieve this, we worked closely with Deconstruct to develop a sequence that maintained the frame’s stiffness throughout the lift.
The jacking process itself took just three days, delivering savings of £2 million and reducing 25% of the programme.
20 Giltspur Street