Case studies 5 & 6 St James's Square, London

5 & 6 St James's Square, London

Overview

Demolition, Environmental Management, Asbestos Removal, Recycling, Temporary Support Works, Civil Engineering

Client:  Exemplar Properties (ph1 works)

Main Contractor:  Sir Robert McAlpine (ph2 works)

Value:  £4.8m

Duration:  70 weeks

The former Lybian Embassy, No. 6 St James Square, was a 6 storey reinforced concrete brick clad Structure, which required demolition to the top of the ground floor. Secondary to this demolition works programme came the removal of the double basements with further excavation to form the new basement, 10 meters below the existing ground level.

Partial demolition was carried out around & within the Grade II* Listed No.5 St James’s Square with the utmost of care taken as the building housed ornate listed plaster ceilings & decorative finishes.

This project was undertaken within on of the most congested areas of London, Piccadilly and was conducted in two Phases. Phase I was working directly for the client and Phase II, as a trade contractor under a novation agreement to the build contractor.

Scope of Works

Phase I – Value £2.1M (34 Weeks)
  • Refurbishment and soft strip of No 5 Including creation of new openings and lift cores.
  • Soft strip and demolition of No 6 using a combination of floor by floor demolition with a 7 tonne excavator working on temporary propped floors, demolishing from 6th floor to first floor.
  • Semi high reach machines demolished the rear multi-storey car park & lower levels of the main building.
Phase II - Value £2.6M ( 36 Weeks)
  • To create a new basement Phase II started by excavating out the central area and then propping of the new slab, This concluded a new triple basement reinforced concrete framed structure.
  • The temporary works used a combination of Zero Piles, Larson steel sheet piles, 4.0m deep underpins to the party walls and justification of the existing reinforced concrete walls to act as the retaining structures.
  • A combination of tubular props, fabricated steelwork and propriety propping systems being used to support them.
  • The excavation was 11.0m deep, generating over 1700 loads of excavated material which was recycled and used in a landscaping project.
  • John F Hunt used a combination of 45 & 20 tonne excavators loading into Lorries, debris conveyor systems and crane lifting skips onto a loading gantry.
  • Additional traffic restrictions by Westminster Council were enforced at the time of this excavation due to Olympic main routes and venues situated near to.
  • Extended loading periods were granted to maintain the contract program and hit the initial finish date.
  • Due to limited access, John F Hunt designed a projecting structure to sustain a 13 tonne long reach excavator. This was a purpose built cantilever gantry in order to remove the excavated material.
  • The Cantilever gantry approach was the quickest, most innovative and cost effective method for this particular inner city project.

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