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24 years

Lewisham Gateway, Phase 1B

Client: John Sisk & Son Ltd
Value: £4.82M
Duration:Ongoing Dec 2015 – July 2017 80 Weeks
Project Type: Residential

Project Description

This is a current ongoing project that entails the construction of the Groundworks and Reinforced Concrete high rise frames to two residential blocks. Block B1 is a 15 storey RC Frame and Block B2 is a 22 storey RC Frame.

Scope of Works

We are engaged by Sisk as a domestic Sub-Contractor on an amended form of sub-contract, JCT Design & Build 2011, with design responsibility for the post tensioned slabs and without any other permanent works design responsibility.

The scope of works comprises installing a piling mat and providing piling works attendance, civil engineering diversion works to the existing river Quaggy, reduce level dig including site waste management, constructing RC foundations and RC cores, installing under-slab drainage, site-wide drainage and services incorporating a surface water attenuation tank and pumping chamber and constructing two number high rise RC Frames – one 15 storeys and the other 22 storeys high – using a jump-form method of construction for the two RC cores.

The river Quaggy is an existing river that runs within the site environs. It is partially culverted under the site area where Block B2 will be constructed. This necessitates the river to be diverted to a new location on site and the existing reinforced concrete culverted section under the proposed foundations for Block B2 to be excavated, broken out and removed from site. These works have been completed on site in conjunction with Block B1 works.

The river diversion was created by the installation of a permanent open cut sheet piled culvert. The works comprised installation of permanent sheet piling to form a culvert, reinforced capping beam to the top of the sheet piling, excavation of the culvert channel, installation of a 500mm thick clay liner, installation of a 200mm thick filter layer (20mm stone) and a 400mm layer of Rip-Rap stone as the finished layer to the river bed. The ‘Rip-Rap’ stone was positioned so as to form a curve in the river.

Once the river diversion was in place we proceeded to break out the existing reinforced concrete culvert, 4.00m wide x 2.40m deep. The void was backfilled with 6F2 imported material, compacted in layers.

We constructed the high rise RC core to block B1 using a jump-form method of construction. All of the suspended RC floors to both blocks are post tensioned with a package value of circa £350k. These have been value engineered by us and designed and installed by our specialist contractor.

The internal staircases to both blocks are cast in-situ using the ‘Flexistairs’ system of permanent formwork.

Block B1 was completed in August 2016 which was six weeks ahead of our contracted programme duration. Block B2 will commence during December 2016.

The scope of work entails:

  • Installing a piling mat and providing piling attendance
  • Bulk excavation and reduce level dig
  • Site waste management and spoil disposal
  • Site logistics management
  • Providing tower crane attendance personnel
  • Under-slab drainage
  • Site-wide drainage and services
  • Storm water attenuation tank and pump chamber
  • Forming a sheet piled culvert for the diversion of the existing river Quaggy
  • Breaking out the existing redundant reinforced concrete river culvert
  • RC Substructures and RC cores
  • Jump-form method of construction to the RC cores
  • Designing and installing post tensioning to all suspended RC floor slabs
  • 2 number blocks, 15 and 22 storeys, high rise RC Frames
  • Cast in-situ RC staircases using ‘Flexistairs’ as permanent formwork
  • GRP mesh grid floor infilling to all service risers




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