projects /

Waitrose

Location

Egham

Client

Liberty Properties / Pochin Construction Ltd

Architect

Lyons Sleeman and Hoare Architects

Completion

Autumn 2019

Project Summary & Objective

A mixed-use scheme comprising 25,000 sq. foot food outlet supermarket comprising basement car parking, housing 166 car parking spaces with three storey 80 bed hotel and plant room facilities.

The key objective was to develop the basement parking whilst dealing with the high-water table within granular river deposits. The incorporation of the road level suspended car park and delivery facility were key challenges during both the design and construction of the facility.

Early procurement of the primary steel frame and therefore coordination of the overlying timber frame and associated loadings was crucial to the procurement programme.

Key Challenges

Following detailed review of the ground conditions and the water table a decision was taken to raft the building in lieu of piling. This was both a commercial and a programme driven strategy. Basement perimeter was designed using street piled walls designed to support the vertical loads from the building perimeter and internal columns were supported of the slab which also provided for the basement car park running surface.

The key challenge was to develop the conceptual design quickly in order to understand whether a raft solution was applicable as commercially this was the best approach. The sheet pile design and the water proofing were therefore key to ensure it was both cost effective and deliverable within the time constraints.

Solution

Tier Consult worked closely with Sheet Piling UK ltd in the design of the sheet piles and the associated water proofing together with waterproof concrete specialists in design of the raft foundation solution.

In respect of the temporary works, Tier Consult worked closely with the sub-contractor appointed to carry out the de-watering operation to enable the raft to be constructed. Additional site investigation was undertaken by Tier Environmental and the result processed to enable the de-watering design to be implemented.

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