Recently Completed Project at St John's College - Barnes Construction

We are delighted to have recently completed the new Community Hub for St John’s College in Cambridge. The project comprised the demolition of the existing 1970s buttery dining room, allowing for the construction of a modern replacement. An area of the Grade-I listed Second Court was refurbished to form a new café and bar space for the College. We are very proud to have delivered a BREEAM Excellent scheme in a listed building, supporting the wider decarbonisation and future proofing of the college estate.

The listed status of the buildings required us to take a careful approach, including the accommodation of weekly inspections on behalf of Historic England. We carried out vibration monitoring throughout to protect the College’s existing structures, including the integrity of a 14th century wall painting of special historic interest. We undertook several measures to minimise vibrations, including saw cutting of floor slabs instead of utilising breakers. Our works included the meticulous dismantling and relocation of a pair of Grade-I listed pillars, which formed the entranceway to the new Community Hub area.

Our site access was through a 3.6 metre high, Grade-I listed gate and over a weight limited Grade-I listed bridge. This required us to carefully consider the size of deliveries, with all loads taken over the bridge by hand. The spider crane utilised for the scheme was disassembled and rebuilt once across the bridge. We carefully programmed all deliveries to ensure that no delays were caused by the process of moving materials to the work area. As we were unable to utilise muckaway lorries, all site waste was removed by hand.

Working within a live college site presented additional challenges to our team. To minimise the disruption caused by our works, we utilised compressed working hours and ceased noise-generating operations entirely during exam periods. Our site compound was located away from the work area, ensuring that it was as inconspicuous as possible. For the College’s May Ball, we dismantled barriers on the route to site and removed some of our compound’s fencing to allow temporary toilets to be placed behind it. We also provided generator power for the event itself.

The project presented a significant challenge due to its emphasis on decarbonising existing heritage buildings. The 500 year old walls of the building allowed significant air leakage, however in improving their airtightness it was of paramount importance to add ventilation and ductwork to aid air circulation and prevent damp. We worked with the wider project team to manage the installation of these systems around the building’s existing timber and masonry. During the construction period, the installation of duct risers through the existing listed structure presented a number of complex issues for our team to resolve, involving negotiation the existing fabric in coordination with heritage consultants.

Sustainability remained a key focus throughout, including in the design of the Buttery’s living green wall, which is fed by collected rainwater. All materials utilised during construction had a low volatile organic compound (VOC) content. We also utilised recycled materials for our site compound and installed bird and bat boxes within the College site. The Community Hub ultimately achieved a BREEAM Excellent rating and is the first Grade-I listed refurbishment in Cambridge to meet this standard, which is a mark of the rigorous attention paid to sustainability by all members of the wider project team.

We initiated a number of processes to support the delivery of a high-quality project. We held workshops for the Buttery roof to explore buildability and the interfaces between the roof and living green wall, and provided samples for many areas, including internal wall finishes and lime mortar. Alongside our own rigorous key stage quality checking procedures, all design disciplines visited site each week in lieu of Quality Inspectors.