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24 years

Lyon Square, Harrow

Client: Redrow Homes
Value: £11.50M
Duration:Nov 2015 – Sept 2016
Project Type: Groundwork and RC Frames

Project Description

The project entailed the construction of a residential/commercial mixed use scheme comprising Groundworks, RC Basement & Substructures and RC Frames to Blocks 1-8, a large shared RC podium transfer slab over the basement with eight RC Cores and Frames constructed over podium level varying in height from 6 storeys to 13 storeys.

Scope of Works

We were engaged by Redrow Homes as a domestic Sub-Contractor on a bespoke form of Sub-Contract with design responsibility for the temporary works.

The scope of work comprised the design and installation of a king post retaining wall system, groundworks, underslab drainage, RC semi-basement and RC substructures to Blocks 1 – 8, installation of an RC waterproof injection system to the basement slab, walls and lift pits, RC foundations for the cores to Blocks 1 – 8, site wide drainage and services which included surface water attenuation tanks, design and installation of temporary works for pit excavation, construction of a shared large RC podium transfer slab to Blocks 1 – 8, construction of 6 number RC low rise blocks, between 6 and 9 storeys high, and 1 number RC high rise block (Block 7), 13 storeys high, where we used a jump-form method of construction for the RC core construction. The construction of Block 3 has been left in abeyance by Redrow Homes until 2017.

The groundworks commenced in November 2015 and the RC superstructure works were completed in September 2016 which was five weeks ahead of schedule.

The groundworks phase of the works was very challenging. The site and surrounding roads were very busy and congested which required careful logistical management. The bulk of the groundworks was carried out over the winter period including all of the deep drainage. There were 10 number surface water attenuation tanks which were installed simultaneously to the RC ground beams and pile caps.

We designed and installed sheet piles and steel bracing/shoring as temporary works for the earthwork support to the attenuation tank pits.

In order to effectively and safely manage our site construction programme for the RC works we created a 3D BIM model. This highlighted all potential problem areas which we dealt with early on. This then enabled us to achieve a completion date that was 5 weeks ahead of our contracted scheduled completion.

Block 6 has an atrium in the podium slab with an 8.50m high floor to ceiling height. We constructed RC columns and walls 8.50m high with an RC corbel built in to facilitate future mezzanine floor construction. We emphasized our working at heights procedure for these works to our operatives by implementing additional tool box talks. All of these works were constructed safely and to a high quality.

The internal staircases to all of the blocks were cast in-situ using the ‘Stairmaster’ system of permanent formwork. External staircases were cast in-situ using traditional formwork.

The RC Basement is a semi-basement with the deepest end, necessitating an RC retaining wall, running adjacent to Lyon Road (Block 6) and St John’s Road (Block 8). We designed and installed a king post temporary works system in order to support and uphold Lyon Road and St John’s Road.

There are six number sewer connections to the existing statutory drainage system.

The Waterproofing system for the RC basement walls, slabs and lift pits was a ‘Rascor’ waterproof injection system.

The heights of the RC Frames to the blocks were:

Blocks 1 & 2 - 6 storeys

Block 3 - not constructed, left in abeyance by Redrow Homes until 2017

Blocks 4 & 5 - 9 storeys

Blocks 6 & 8 - 7 storeys

Block 7 13 storeys

The scope of works entailed:

  • Site logistics management
  • Site waste management and spoil disposal
  • Design and installation of a king post temporary works retention system
  • Design and installation of temporary works to the attenuation tank pits
  • RC core, ground beam and pile cap excavation
  • Provision of tower crane attendance personnel
  • Under-slab drainage
  • Site wide deep drainage and services
  • 10 number attenuation tanks
  • 6 number sewer connections to existing statutory drainage
  • RC Cores, lift pits, RC Basement retaining walls and slab, RC sub-structures
  • Waterproofing system – ‘Rascor’ injection system to RC concrete basement & lift pits
  • Interpolating and utilising BIM
  • RC podium transfer slab / deck – 6200m2, 600mm thick
  • Atrium in podium deck, 8.50m high – RC columns & walls 8.50m high with an RC corbel cast integrally to facilitate future mezzanine floor connections.
  • Jump-form construction to Block 7, RC Core, 13 storeys high
  • 6 number blocks, varying in height from 6 to 9 storeys high, low rise RC Frames, Blocks 1, 2, 4, 5, 6 & 8. Block 3 is left in abeyance by Redrow until 2017.
  • 1 number block, thirteen storeys high, high rise RC Frame, Block 7




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