Stratford Halo

Project Overview

A mixed development by the Genesis Housing Association, 150 High Street, Stratford, is a landmark regeneration project for London, located at the approach to the 2012 Olympic Games.

Providing 704 homes, the scheme includes five new residential blocks, one of which, at over 132 metres, will be one of the highest residential towers in London.

The redevelopment will provide a mix of flexible commercial space, community facilities plus associated car and cycle parking, landscaped public, communal and private amenity space and a new landscaped riverside walkway.

The redevelopment incorporates seven blocks of between  7 and 43 storeys, surrounding private and communal courtyard spaces within the southern and northern sections of the site respectively. The scheme will create new frontages on to High Street and Warton Road, whilst the courtyard spaces will open to the west to address the Waterworks River.

Currently all the blocks are underway, with blocks F and G due to be completed imminently, and all other blocks due for completion towards the end of 2012.

150 High Street is one of the only schemes of its size in the UK being constructed under a lump-sum fixed-price design-and-build contract.

Procurement

As an experienced contractor specialising in high-rise construction, Ardmore negotiated the project in the early stages and, following extensive value engineering, was able to submit a lump-sum, fixed-price tender, despite having very limited architectural planning drawings and no structural engineering drawings. With the contract sum agreed, Ardmore commenced piling within seven weeks.

Construction Methodology

The one to two-storey basement has been formed using Continuous Flight Auger (CFA) piled walls, tanked with a Voltex Bentonite water proofing system. With the site bordering a tributary of the Thames, extensive de-watering was necessary during excavation. Following this, the CFA foundation piles were cast at the lower level.

The tower core walls will be slip-formed and the flat slab reinforced concrete (RC) frames of the residential blocks will be formed off a transfer slab at ground floor level. The 10-storey blocks will comprise a mixture of stone, brick and glass cladding, with the 43-storey tower clad in a unitised glass curtain walling system with architectural bull nose features.

The lightweight metal inner skin of the external envelope will be raised ahead of the cladding to secure watertight conditions and allow fit-out to dovetail with construction of the RC frame.

This integrated approach, combined with Ardmore’s prefabricated kitchen and bathroom pods, will enable rapid fitting out and early phased handovers.

Value Engineering

Ardmore has developed a flat, thin slab RC frame with slimline columns hidden within party walls. By omitting floor screeds and developing extremely lightweight dry-wall partitions, Ardmore has achieved savings of over 25 per cent in the amount of piling required.

Among other enhancements, all cladding systems have been value engineered and elevations rationalised to maximise prefabrication, while revising the design of the basement car park and relocating the central plant room will reduce primary service runs. The combined heat & power (CHP) plant, gas and biomass boiler systems were also revised to generate considerable cost savings.

Value Enhancement

By reworking the floor plans to increase the size of residential units and relocating the plant rooms from the roof to the basement, more units within the same footprint can be achieved, adding significant value to the project.

Sustainability

CHP plant, biomass boilers, rainwater harvesting and green and brown roofs, as well as water-saving sanitaryware, have all been incorporated within the scheme, together with considerable areas of water attenuation on the 1.3-hectare Thames-side site.

Hand-over Strategy

Instead of a block-by-block handover initially proposed by the client, Ardmore suggested a floor-by-floor handover, enabling occupations 18 months faster. And, by relocating the plant rooms, fitting-out could also take place far earlier. The tower core will be slip-formed and the central corridors and stairs formed in pre-cast concrete, allowing early installation of lifts and enabling phased occupation of the lower levels as fit-out continues above.

Key Achievements/Innovation

Through its expertise and experience in developing the structural and façade design in advance of the construction programme, as well as introducing early temporary watertight solutions and design revisions, Ardmore has ensured fit-out – and client handover – can begin at the earliest opportunity.