Bath Quays South – No.1 Bath Quays

Bath, UK

Project details
Client

Bath and North East Somerset Council

Architect

Penoyre & Prasad

Duration

5 years

Services provided by Buro Happold

Bridge engineering and civil structures, Environmental consultancy, Ground engineering, Structural engineering, Water

Bath Quays is a flagship regeneration project that will establish a thriving commercial quarter at the heart of this UNESCO World Heritage Centre.

Overlooking the River Avon, Bath Quays South is a focal element of this transformative initiative. Conceived to address the city’s shortage of grade A office facilities, this development mixes historic and modern architecture to produce an inspiring environment for creative minds. 

The site encompasses a new office building, No.1 Bath Quays, alongside the refurbished Newark works and a second future phase of new build. A river bridge for pedestrians and cyclists will connect to a sister development, Bath Quays North, and provide easy access to the city centre.

No.1 Bath Quays is the first new office block to be built in Bath for 25 years. It will provide 45,000ft2 of grade A space along with storage for more than 100 bikes and secure parking. 

Challenge

From a structural perspective, this office building is fairly straightforward – it consists of a five-storey concrete frame with flat slabs supported on a 7.5m column grid and a concrete core. There is a small cantilever on the south facade at the upper levels requiring some downstand beams; the ground floor is slightly sunken into the ground to provide clearance for cars to pass under an area of raised courtyard. Ultimately, it proved to be the site – rather than the structure – that provided the engineering challenges for our geotechnical experts to resolve.

First, the general ground conditions necessitated serious consideration. There is approximately 3m of made ground over a layer of alluvium and soft clay. Given the significant depth of softer material, the office building has a suspended ground floor slab; the building is supported on piled foundations. Below these soft layers there are river terrace deposits before the Charmouth mudstone is reached. Bands of harder limestone have been found within the mudstone, which made either standard piling or sheet piling difficult.

Secondly, as piled foundations are required, the County of Avon Act 1982 comes into force. This Act requires special permissions for any construction works carried out below a certain depth from ground level, depending on proximity to known sources of artesian waters – hot springs. This site is sufficiently close to the springs to require permission for works greater than 5m below ground level – the building piles, along with sheet piles for a flood wall, both penetrate lower than this.

External shot of new office block at Bath Quays during construction
Located in a prime riverside location at the heart of the city’s flagship regeneration project, No.1 Bath Quays will be the first purpose-built office building in Bath for a generation. Image: Buro Happold

Solution

Addressing the ground condition challenges, advice from the supply chain resulted in larger diameter continuous flight auger (CFA) piles being selected for the office as a rig capable of cutting through the limestone – if encountered – was required. 

As regards the County of Avon Act 1982, the CFA piling method was generally acceptable because the method of installation is such that any soil displaced is immediately filled with concrete. However, the sheet piles are pre-augured to get through the limestone bands. There was a concern that this could create pathways for artesian waters. Accordingly, the solution requires the sheet piles to be grouted in to close these off.

The office building project is being procured under a design and build contract. Buro Happold produced a scheme to stage 4 level of design. BAM are the contractor – they are using BAM Design to take the design through to construction. Buro Happold is assisting BAM with obtaining permits from the Environment Agency, so our water engineering team is working with both the client and contractor.

Value

The client is benefitting from specialist expertise being applied by a multidisciplinary team working across the Bath Quays South development. This is a complex undertaking that interfaces with several neighbouring projects being procured separately. Buro Happold has facilitated communication between all relevant parties and stakeholders to ensure that the interfaces are coherent while coordination is maintained. The creation of such quality office space – set in tranquil surroundings with a degree of urban bustle – will help to enable Bath to evolve as an exceptional place to do business.