Delivering a highly complex construction project within a city centre known the world over for its outstanding architecture and iconic skyline undoubtedly brings a certain added pressure to a job.
With its flowing, freeform design, Gradel Quadrangles for New College Oxford, is a contemporary reimagining of the classic quadrangle model.
The state-of-the-art scheme comprises a three-storey quadrangle of student accommodation, new school buildings, porter’s lodge and landmark 21.5m tower, and features a complex, high-quality limestone and sandstone facade.
Below are some of the highlights to date.
Brave roof redesign delivers a better outcome
Originally, the main quad building was to have a sprayed concrete roof. As we moved into the technical design stage, we looked to explore a safer, more cost effective and low carbon approach.
In full consultation with the college, we took the brave decision to redesign the roof, collaborating with our architect and structural engineers to explore six alternative construction types and some 15 different coverings.
Desktop, cost, and programme studies were also undertaken to see which new solution would work best, before samples and mock-ups were produced.
We then engaged with the college’s steering group to successfully negotiate replacing the original design with an equally striking glulam timber structure, with tessellated aluminium tiles. This alternative solution delivers the modern aesthetics the college and architect were looking for, is cheaper to build, delivers three months reduction of programme and minimises the level of embodied carbon.
In support of the College’s commitment to achieving Net Zero Carbon by 2035, the project team sought to deliver savings in embodied and whole life carbon across the board, as a result of which, they were recognised by the ICE Carbon Champion programme. Measures have included:
- Using our BIM model to obtain building material quantities, which combined with Environmental Product Declarations (EPDs), were used to perform a whole life carbon assessment.
- A comparison of EPDs demonstrated that our alternative roof design delivers huge carbon savings compared to the original concrete proposal. (approx. 197t CO2e)
- To reduce the embodied carbon associated with the piling, the design team specified a concrete mix with a high percentage of Ground Granulated Blast Furnace Slag (GGBS) (>50% in mass). This achieved a 52% reduction of CO2e from piling, when comparing to a standard Portland Cement mixture.
- Using our Tracker+ carbon capture tool to capture project sustainability data from our supply chain. This has enabled us to assess what was actually installed against what was proposed at the design stage.
Overcoming façade complexities
The development’s curved and free-flowing buildings feature diamond-shaped block stone facades, with each stone curved on both faces. Achieving the strict quality thresholds required to deliver this unique precision façade represented a significant construction challenge. We undertook a detailed 3D BIM model of each stone block which were then carved in exact geometrical proportions using 5D CNC saws. This was all done offsite, reducing waste and avoiding noisy and dirty onsite stone cutting.
Our team has also had to effectively manage our engagement not only with the college’s large steering group but with the client’s project team, senior College decision makers, Oxford City Council and local residents. The team have worked hard to ensure that through excellent communication and consultation all key stakeholders are involved at every stage and their feedback is given the utmost attention.
With a year to go on the project, works on the basement of the main quadrangle building are nearing completion, with the ground floor decking progressing well as the team’s focus moves to constructing the floors above. The tower structure is complete, with the falsework in the process of being removed.