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Located off Trentham Street, the site is in the heart of a regeneration area of Manchester and one of a handful of developments bringing new life to a run-down area overlooked by the Cornbrook tram stop.

Designed by Sheppard Robson Architects, the two residential blocks rise to 15 and 14 storeys and feature 280 apartments for private rent with retail at ground floor level.

Design ID were introduced to the project by the Contractor GRAHAM to review the initial tender design produced by the Clients Design Team for risks and opportunities and to take the design forward from RIBA Stage 2/3 to completion. Design ID took forward a concrete frame structure, with CFA piles supporting ground beams and a suspended cast insitu concrete slab for the ground and upper floors.

To incorporate elements of off-site construction, Design ID designed precast concrete columns and precast concrete twin-walls unlocking both cost/programme and environmental benefits in line with the specialist contractor’s sequence and construction methodology. Precast concrete vertical elements support insitu concrete flat slabs with a perimeter cladding system.

A primary project headline is how Design ID managed to unlock significant material savings on the project. Responding to Design ID commitments after becoming a Structural Engineers Declare signatory, acknowledging the climate emergency and IStructE published guidance on the contribution of the structure on overall embodied carbon, Design ID reduced overall concrete consumption from the original tender scheme produced by the previous Clients Engineer.

By considering the overall construction programme, and working closely with GRAHAM to determine the main frame and cladding installation construction sequence, the period of time between the slabs being cast/struck and cladding being installed could be accurately assessed. By applying some innovative thinking, Design ID could ascertain how much deflection and subsequent creep would occur pre-cladding and therefore how much deflection would need to be accommodated by the cladding post installation.

Turning a traditional consideration of structural deflections for cladding into a pre-cladding installation tolerance, Design ID were able to reduce the deflection limits for the structural slab edges. Coupling this with some detailed finite element analysis Design ID were able to reduce the thickness of each floor slab by 15mm. Whilst a modest reduction per floor, when applied over fifteen stories the result was a reduction in concrete volume of nearly 300m3 and the removal of nearly 50 construction vehicle movement from the streets of inner city Manchester.

The project demonstrated that embodied carbon savings can be realised by lean design coupled with innovative thinking associated with construction programming and sequence, and can be unlocked by taking a collaborative approach including targeted pre-construction engagement with the Main Contractor and Supply Chain.