The Catalyst Building, designed by Feilden Clegg Bradley Studios, is the sort of challenge that academic estates like to set architects.
Staffordshire University wanted a low-energy building that could house diverse social, study and support functions under one roof, and be readily adapted as its needs evolved.
FCB Studios partner Hugo Marrack describes the Catalyst as preparing for, or even inviting, the “unknown brief” of the 21st century. “We wanted to develop what we called a framework building: as open-plan as possible, with as few columns as possible, long spans, concrete frame, exposed soffits, and all the services in raised access floors – that was the strategy.”
Today, the ground floor is a largely double-height zone with a foyer, cafes, gallery and a mezzanine at the back containing smaller meeting rooms. The upper two levels house quieter study spaces, offices and more specialised areas such as data labs. But in the future, that can all change, particularly if the university wants to attract different types of businesses and apprenticeships.
“It’s nice knowing that you're designing a building that, in theory, has 100-plus years of life in its frame,” says Marrack. “It can be reused, knocked about, moved about. You can start imagining it having three or four lives.”
The frame may be robust enough to survive a knockabout, but it’s also lean. The grid is based on spans of 7.2m, rising to 10.8m to allow larger, open spaces at each end of the plan. Post-tensioning combined with very subtly coffered soffits has resulted in slab depths of 275mm, or 300mm including the coffers’ understated downstands. This represents a reduction of up to 250mm as, prior to adopting the post-tensioned slab design, the scheme had slab depths of up to 550mm in many locations, such as structural grid lines.
The coffered soffits not only help to minimise the amount of concrete in the structure, they also helped with the setting out. A proprietary formwork system was used to cast the slabs in sections of 1.8m x 1.8m, conforming to the 7.2m grid. However, as the first-floor slab was poured, the formwork dimensions were found to be fractionally off. Across the length of the building – some 106m – this accumulated to an overall 40mm discrepancy. If repeated on the upper storeys, it would have affected the planned locations of the dropdown lighting, partitions and other fittings.
The key to resolving this issue was the coffers. Reusable 1.2m x 2.4m sheets of plywood were laid onto the formwork system for the remaining floors, essentially covering over the system’s fixed joints. “The coffers were originally about creating relief in the soffits, but they have also solved a lot of the accuracy challenges,” says Marrack. “Because you never see the formwork joints, it doesn’t matter if the recesses nudge along a bit.”
They have performed their aesthetic role too. The plywoods panels have left a matte surface with minimal grout loss and staining, contrasting with the slightly shinier finish of the downstands, which were cast directly against the phenolic-coated formwork system. This has helped to accentuate the coffered pattern, while a greater sense of depth was also generated by chamfering the plywood’s sides, effectively elongating the edges of each recess to 45mm.
Externally, the Catalyst is clad in precast panels faced in red and blue Staffordshire bricks: glazed reds on the double-height ground floor, with variegated reds above and recessed panels of variegated blues framing the glazing like curtains. Despite using brick slips, the architects still wanted the feel of a monolithic structure: “It was important that it looked the way it was built, with posts and beams stacked and sequenced,” says Marrack.
On the first-floor beam and columns, half bricks are cast into a 50mm backing of high-strength glass-reinforced concrete. The corner details show a full brick end and each structural element is five brick lengths deep. The beam’s 7.2m and 10.8m-long sections line up seamlessly with the in-situ concrete frame behind, with the discreet joints landing precisely halfway along each column. It has the effect of a single beam, stretching the full 106m length of the facade. “All the joints had to be exactly where they needed to be,” says Marrack. “None of them are trying to hide.”
The blue-grey panels above, with alternating embossed and debossed bricks, add an element of relief to the building’s otherwise solid presence. These are shallower brick slips, cast onto a 125mm concrete backing, and were delivered in double-height sections 7.5m tall – a job made easier by the fact that the manufacturer, Thorp Precast, is based just three miles down the road.
The university was keen to keep the project as local as possible, investing 50% of the budget within 30 miles of site. This was part of a sustainability strategy that targeted local employment and training, as well as operational energy, waste and recycling. Marrack says that the detailing alone saved £1 million on the facade by ensuring that there was no wastage on the brick slips, using both faces and “making every brick work hard”.
About 3,000m² of crushed material from the demolition of the previous building on the site was reused to form the pile mat, and salvaged timber was used as falsework and formwork. The in-situ concrete contains 25% GGBS – the short project window and longer curing times of GGBS concrete precluded higher proportions of cement replacement.
The building is all-electric, with a roof-wide photovoltaic array generating 20% of its energy requirements. Heating is provided via air source heat pumps, while the exposed thermal mass of the concrete frame mitigates temperature fluctuations and regulates summer peaks. Services consultancy Max Fordham says that, even without full air-conditioning, it performed well in last summer’s unprecedented heatwaves.
The Catalyst’s embodied carbon has been measured at 700kgCO2eq/m2, while annual carbon emissions are forecast to be 12kgCO2eq/m2. This isn’t the end of the story: Max Fordham is undertaking post-occupancy evaluation to help analyse and optimise the in-use performance. And as Marrack points out, it’s the sort of building that’s ripe for reinvention. “It's good fun working with these kinds of frames. It would be a nice one for someone to take on as a refurb project in 30 years’ time.”