Case Study: Building beneath London

When working on a basement excavation project in London, the ability to adapt to changing site requirements is essential. When the project is of the size of Salisbury Square, this becomes even more paramount, with Keltbray relying on our expertise, innovation and comprehensive temporary works offering.

Large central-London basement excavation with major temporary works challenges.

Bespoke high-capacity propping system designed to support deep construction.

Early collaboration enabled safe, efficient delivery in a complex urban site.

The challenge

Complex city-centre excavation: A large 5,000 m² basement project at Salisbury Square required temporary works to manage heavy loads, tight logistics, and sensitive surrounding infrastructure in central London.

Excavating a three-storey basement created significant lateral pressures and load demands on the retaining walls. The temporary works system needed to safely resist these forces while enabling construction to proceed at multiple levels. 

Located within London’s historic Square Mile, the project was surrounded by sensitive buildings and existing underground infrastructure. 

Our solution

Our temporary works solution combined a range of our Super Bracing Struts (SBS), from 400mm to 1000mm, alongside our Supershaft Plus bracing system and Steel Waler Frames to manage the significant loads of the project. Recognising the need for even greater capacity, we designed and developed a bespoke 1200mm diameter prop—the largest of its kind—specifically for this scheme.

Early collaboration with the project team was vital, allowing us to deliver the temporary works design 12 weeks in advance while maintaining flexibility to adapt the prop design as new site data emerged. We also re-engineered our hydraulic screwed ram jacks, traditionally used above ground, to integrate with the new props and achieve the required high load capacity.

In addition to designing and supplying the temporary works equipment, we worked closely with Keltbray’s site teams to ensure seamless installation and performance. Our in-house hydraulic jacking team handled the pre-loading of the props and jacks, ensuring precise installation and safety.

“Salisbury Square is a great example of collaboration, a complex ground engineering project with technical constraints and logistical challenges being in the city centre. The proactive approach has made the process easy, with great coordination with our in-house temporary works designer Wentworth House Partnership. Salisbury Square is a great example of both business’ engineering capabilities.”

Sinan Atasoy / Project Director/ Keltbray

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Disclaimer: This project was completed by MH International’s parent company using shared personnel, under an intra group informal licence.