77 Welbeck Street, London, W1G

Marylebone Lane LP

91 weeks

£16m

London, W1G

Location & Overview

Deconstruction of an architecturally prominent, brutalist style 10-storey pre-cast concrete car park in Welbeck Street, located behind Oxford Street and close to the underground station, in a heavily pedestrianised location. Piling, bulk excavation of 20,593 m³ and construction of a 17-meter deep, 4-storey basement box. Asbestos removal, soft-strip, service isolations. Top-down demolition of the structure using a range of techniques due to the constrained location of the site, continuing down through the ground floor, including below-ground demolition of two basement levels. Pile Probe to the perimeter of the site ready for the secant piled wall. The basement was backfilled with crushed concrete to form a piling mat platform. Design, supply, and installation of temporary works. Construction of a 17m deep 4, storey basement box back to ground level, requiring a 900mm secant piling enclosure. Excavation of 20,590 m³ of spoil for substructure formation. Slipform construction of central core and 9-storey reinforced concrete frame.

Work, Challenges & Solutions

This was a logistically demanding, city-centre project in a sensitive, busy area surrounded by occupied commercial and residential buildings. Due to the site’s proximity to Oxford Street, two Grade I and II listed buildings, and the Stratford Place Conservation Area, the job required collaboration with environmental officers, and extensive party wall agreements were obtained to ensure our methodology was within their requirements and that of Historic England.

We arranged licensing and agreements for pavement, hoarding and parking bay suspension, and our logistics plans were created collaboratively to ensure deliveries did not impact the local businesses.

Maintaining good, safe pedestrian flow in areas of heavy footfall due to Oxford Street’s proximity.

During a value engineering exercise, we proposed a design change, amending the secant piled wall design to work with 2 levels of props being installed from a reduced piling platform level. This converted the semi-top-down “Doughnut” basement solution to a traditional bottom-up basement construction.

Due to logistical constraints, we implemented an alternative logistics strategy, which involved the installation of a corner gantry, allowing tippers access directly from the road, resulting in a four-week programme reduction and seven-figure saving for our client.

Working with an extensive multi-stakeholder team, ‘Adoodle’ software was implemented to successfully manage design information, document management and workflow. This streamlined the process of gaining comments, responses, and amendments from team members based in different sites and offices, therefore reducing duplication and increasing clarity for all involved.

Achievements

The site was registered with the considerate constructors’ scheme with a rating of ‘Excellent’.

Due to our in-house expertise, we phased demolition and enabling works concurrently to save time on the programme.

In excess of 6,000m3 of demolition arisings were removed from the site for recycling.