The new Interdisciplinary Biomedical Research Building (IBRB) at the University of Warwick is all about joining things together.
It’s a gateway building, sitting on the junctionbetween the Gibbets Hill campus and its surrounding woodland. It’s a meeting place, with landscaped external seating, open work areas and a welcoming double-height ground-floor cafe. Most importantly, it’s a merger of research disciplines, housing both the medicine and life sciences departments, in a move that the university hopes will inspire cross-fertilisation of ideas and research.
So it’s appropriate that the IBRB is a hybrid building, with two distinct but connected structures: an eastern volume clad in anodised aluminium, and a larger western volume wrapped in white precast concrete. The external appearance reflects two different structural systems. The smaller volume is a timber entrance pavilion with a processional staircase and open areas for researchers to write up their experiments. The larger concrete block houses the laboratories, as well as a 400 seat lecture theatre and the cafe.
“The concept came from seeing that there are essentially two halves to the building – the wet laboratories and write-up spaces – and that they have quite different requirements,” says Jason Martin, partner at architect Hawkins\Brown. “The labs need a very stable environment with large spans and tall spaces because of the amount of servicing.” For the write-up spaces, the architects wanted a more relaxed atmosphere and a strong visual contrast, so opted for exposed timber. “We really wanted to express both structural systems as much as possible, and enjoy the different feel of the two spaces.”
The concrete structure is almost entirely precast. From the start, Warwick wanted the IBRB to be a flagship sustainable building for the campus. As part of this, it wrote into the brief that at least 50% of the project’s value should be constructed from premanufactured components, thereby reducing waste on site and ensuring materials would be used as efficiently as possible. An offsite-manufactured project had the additional advantages of speeding up the construction programme and requiring fewer staff and heavy machines on site – key considerations on a busy university campus.
The concrete frame was designed as a kit of more than 1,300 bespoke precast parts. The main vertical elements are storey-height wall panels, 3.6m wide, up to 6m tall and 250mm thick, and weighing as much as 20 tonnes. These meet floor plates constructed of 7m-long, 250mm-deep prestressed hollowcore slabs – a structural solution designed to reduce the load on the transfer beams that stretch 16m over the ground-floor lecture theatre. In-situ reinforced structural toppings, 100mm thick, were also applied to the floor slabs to stiffen the slab, share the distribution of loads and reduce vibrations in the sensitive lab areas.
The concrete for the precast frame components contained both a limestone filler replacement and GGBS binder replacement, reducing overall cement content by 35%, while the structural toppings contained up to 50% supplementary cementitious materials in the cement. The kit of parts proved quick to assemble. In 12 months, an empty site became an almost complete building, with six weeks cut from the programme despite the onset of the Covid-19 pandemic. The contractor, Willmott Dixon, believes there were 100 fewer site deliveries, and the more efficient use of material saved about 850 tonnes of concrete overall.
But it’s also clear that this is a highly crafted structure. The main entrance is on the timber-framed side of the building, but visitors are immediately faced with an expansive concrete wall signalling the junction of the two volumes. The concrete has been cast with a corrugated vertical finish, created using Reckli flexible mould liners, which accentuates the contrast with the timber. “Because we had such large areas of concrete, we didn’t want it to just have a simple, fair-faced finish,” says Martin.
“It has an almost curtain-like quality, which gives the impression of something much lighter than it actually is. And you get a beautiful play of light across the surface.” The building follows the natural slope of the site, so stairs from the 6m-high entrance hall lead down to an even taller ground-floor space in the concrete building. The corrugated walls continue along the stairs and into the cathedral-like cafe that occupies this lower space.
The concrete has two faces
The sheer size of the wall panels posed some of the biggest challenges from a precasting point of view – particularly when it came to casting the distinctive textures into the surface. Some of the 8m-tall panels between the lecture theatre, the cafe and the stairwell are double-faced, with the corrugated effect on one side and a boardmarked pattern on the other.
“Normally if we are creating two faces we would cast them in a vertical cell, what we call a battery mould, which creates a finish on both sides of the wall,” says Simon Harold, development director at concrete contractor PCE. “But because of the size of the panels, we didn’t have a mould big enough to do that.” Instead, a complex process was devised, in which the panels would be cast flat on a table in two halves. “We cast half the panel in section, with reinforcement sticking out of it.
Then the next day, we turned it over and added another layer of concrete and a mould with the other finish on it. Aligning a geometric pattern, 8m long by 3m wide, was quite tricky.” Transporting the finished panels the 40 miles from factory to site also proved a delicate operation. “You’ve got to be very, very careful when you’re handling the walls.
We try to transport them on an edge, but because of their size we had to move them landscape and then spin them upright on site.” After the panels had been manoeuvred into position, large props were craned in to support them until they could be stitched together with a vertical joint.
At over 9m high, these walls were too big to cast as single panels, so a discreet joint has been placed 1m above the floor, aligning neatly with the high benches that line the space. Views out to the surrounding woodland are framed by full height columns, just 250mm wide, which stretch up into a 2m-high open service space furnished with neat rows of vertical acoustic baffles. The cafe leads to the 400-seat lecture theatre, which is embedded into the slope behind a 5m-high in situ concrete retaining wall.
Timber wall cladding is interspersed with further moments of exposed precast concrete, which here has a boardmarked finish, again created using a standard Reckli formliner. What makes this particularly impressive is that the other side of the same wall panel, flanking the staircase, boasts the corrugated finish (see box, left). Above the ground floor are three levels of category 2 lab spaces, where scientists will explore how cells and tissues perform mechanical functions, with wide ranging implications for a range of diseases, from cancer to brittle bones and heart conditions.
These highly functional spaces benefit from the longer spans and 4.5m floor-tofloor heights of the concrete frame, which accommodates an impressive 1.2m-high servicing void. The highly complex services are another area that has been almost entirely manufactured off-site. Some 120 horizontal modules slot into the ceiling space and provide all services to the labs. The modules all plug into a 27m-high prefabricated “mega-riser” – claimed to be the largest of its kind to be installed in Europe. The riser has a 5m x 4m footprint and came in six sections, lowered in from above by crane.
The installation took four people two days, rather than the 18-week, 10-person job that the contractor had programmed in. What made this possible was the pinpoint accuracy of the precast frame. “To be able to slot the riser all the way down five storeys, we needed to work to critical tolerances,” says Simon Harold, development director at concrete contractor PCE. “If you cast a concrete wall, and it’s out, you know you’re in big trouble. We were able to build the shaft to within less than 10mm.” A number of connections were incorporated into the structure so that the riser could be restrained and fixed into position very quickly. Because no back-propping was needed, work could continue safely in the areas around the riser straight away.
The accuracy of the precast frame was also crucial to connecting the two structures. The timber is fixed to the concrete structure with castin steel fin plates hidden behind a shadow gap, a gentle illusion that softens the meeting point between the materials. The timber beam fixing position could be adjusted on the fin plate to take up the tolerance deviation and enable the beams to be perfectly aligned. “Again, we were able to design the connections around very tight tolerances,” says Harold, “which meant we didn’t have to accommodate so much movement and could rationalise those details.”
The facade is similarly controlled, with a number of raised vertical details, neatly aligned joints and thoughtful contrasts between smooth, grit-blasted and acid-etched finishes. “We were able to work in that extra level of texture,” says Martin, “and also create some quite heavy profiling to highlight areas such as the cafe. That’s the sort of detailing you can only really do in precast.” In total, 149 single-skin panels cover more than 2,800m2 of the facade. The ground-floor units are about 6m high and 3.3m wide, while the upper levels were cast as doublestorey, 9.3m-high panels. The glazing was pre-installed, with solid halfpanels either side completing the unit. The vertical joints between the units are subtly shaded by 300mmdeep projecting fins, which bring a rhythmic elegance to the ensemble and shield the windows from the afternoon sun.
The precast solution came into its own during the cladding programme, carried out just as the UK was forced into lockdown, as fixing the panels to the structure involved relatively little manual work. “Remarkably, they lost very little time during that period,” says Martin, “because they were able to maintain the 2m distance between operatives on site.” In all, a site team of about 20 people and a single tower crane have been able to piece together an impressive piece of architecture. In a building that’s all about joining people together, this assemblage of columns, slabs, beams, wall and cladding panels is perhaps the most impressive connecting act of all.