Cecil Avenue

Innovative geotechnical solutions to cut programme and enhance buildability

The Cecil Avenue development is a £92 million scheme led by Wates Residential in partnership with Brent Council, delivering 304 new homes across two sites.

The main site, formerly Copland School, features a mixed-tenure courtyard development of five- to nine-storey buildings, providing one- to four-bedroom apartments and maisonettes, complemented by commercial spaces and community facilities. Half of the homes are designated as affordable housing, with the remainder for private sale.

Engaged by Wates as the developer, Walsh provided geotechnical and structural design, addressing complex site challenges to enable the safe construction of a 7.5m-deep basement. Close coordination between Walsh, Wates Residential, GCL, and the wider supply chain ensured seamless integration of geotechnical and structural solutions. By proactively engaging with all stakeholders, we delivered a solution that optimised buildability, safety, and cost efficiency.

With a value of approximately £900k, the geotechnical works were crucial in keeping the project on schedule and within budget.

Overcoming Geotechnical Challenges

Located 90m south of the Wembley Hill Railway Cutting—historically significant for a major slope failure in 1918, later studied by Prof. A.W. Skempton in his seminal work on slope stability—the site posed considerable geotechnical risks. The geological profile, comprising Dollis Hill Gravel over London Clay, presented instability concerns due to periglacial slip surfaces. Safely excavating the basement required a solution that balanced technical complexity with efficiency.

Rather than deferring temporary works to the contractor, we took the lead in integrating a geotechnical solution that minimised disruption while maintaining safety. Instead of relying on a traditional internal propping system—often complex and restrictive—our design utilised permanent piles to provide temporary lateral support to the rear of the sheet-piled wall. This eliminated the need for additional temporary retaining structures and created an unencumbered excavation area, improving buildability, reducing complexity, and maintaining programme efficiency.

Innovative Design & Real-Time Monitoring

Our design-first approach integrated permanent and temporary works from the outset, delivering a geotechnical solution that was not only technically robust but also highly efficient. By adopting real-time monitoring and the Observational Method, we ensured that ground movement and stability were continuously assessed, allowing for adjustments based on actual site conditions rather than overly conservative assumptions. This proactive risk management approach resulted in:

Enhanced safety:

Early detection of ground movement reduced risks to workers and infrastructure.

Dynamic risk management:

Adjusting excavation methods in real-time improved efficiency.

Technical reliability:

Monitoring validated the design, ensuring it performed as planned.

KEY ACHIEVEMENTS

This innovative geotechnical approach delivered measurable benefits across cost, time, and sustainability:

Cost Savings:

Avoiding unnecessary temporary works reduced material costs, improving cost control.

Programme Efficiency:

Eliminating internal propping simplified excavation, shaving eight weeks (6.5%) off the programme.

Quality Assurance:

Real-time monitoring confirmed slope stability and validated the design’s success.

Health & Safety Leadership:

A comprehensive risk assessment and staged trigger system minimised uncertainties, ensuring safe excavation and long-term site stability.

Sustainability:

Reusing permanent piles reduced material waste and embodied carbon, aligning with Brent Council’s low-carbon objectives.