Roger Bullivant (RB) has completed the piling works for the £16.5M redevelopment and restoration of York’s historic Guildhall site.
The Guildhall complex situated on the River Ouse contains Grade I and II listed buildings built around a 15th century hall and riverside meeting room, with parts dating from 1445.
The works carried out by the City of York Council and contractor Vinci Construction on the listed site are the first in over 60 years.
RB delivered the design and installation works for the crane base mini piling, underpinning piling, and sectional flight auger (SFA) mini piling which uses an auger that is made up of shorter sections of hollow stem continuous flight auger, for the proposed South Range and North Annexe buildings.
Restricted access to the building was a major challenge for the project since the site could initially only be reached via the front entrance through a small brickwork corridor from a restricted access road.
Plant and construction methods were therefore carefully selected to make use of the restricted width alleys that give access to the site.
The river was used for deliveries and a tower crane was erected on site to enable plant and materials to be lifted into the work area from a barge.
For the piling engineering, RB installed 220mm bottom driven mini piles to depths of 14m onto sandstone rock head.
For the South Range new build section, RB installed 12 sectional flight augers measuring 300mm. Because of access restrictions, RB installed piles using batched grout.
For the North Annexe, RB installed 56 sectional flight auger piles measuring 450mm each. A small concrete wagon and pump gained site access via the enclosed alleyway off Lendal to complete this section of the work.
Due to historical movement RB was required to underpin the existing North Annexe Tower to allow the new North Annexe to be constructed.
An old brick arch was discovered within the makeup of the main wall during Vinci Construction’s excavation works for the ground beams. This led to a major redesign which involved stepping underpinning down in the arch and then returning to its original level beyond the arch. RB installed 16 piles measuring 220mm each for the tower crane.
The discovery of the arch made the access problems to the site worse as this resulted in further reduced levels. However, Vinci provided scaffold access and a lifting gantry to gain access to the underpinning area.
Upon curing of the underpinning system, vibration-free jack piles were installed using the dead weight of the structure.
Vinci Construction UK project manager Steve Dingley said: “The piling has been completed successfully and professionally by the Roger Bullivant team within what is a very constrained site, the team consistently provided solutions to overcome the challenges that we faced”.
City of York Council assistant director of regeneration and asset management Tracey Carter said: “This unique project requires firms who are willing to work on a complex, historic site, with precision and within a tight city centre location. We’re pleased to see the piling completed, forming the foundations of the new buildings.”
The redevelopment and restoration of Guildhall was shortlisted in the UK Project with a Geotechnical Value of up to £500k category at this year's GE Awards.
The project ended in early November 2021 after 23 weeks of works, with all piling works delivered on schedule.
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