In 2021, British universities were faced with an accommodation crisis. Because of the Covid pandemic, adjustments had been made to the A-level marking system and many more candidates than usual attained their grades. Universities were obliged to honour their offers – but where to put the extra students?
The University of York was already building the £130m Campus East Gateway – a set of 18 three and four-storey blocks, which would provide 1,480 rooms. Was there any way, wondered York, of delivering some of that accommodation early?
In the midst of the pandemic, with sites and factories closed or struggling to maintain interrupted schedules, this may have seemed a forlorn hope. Nevertheless, it is exactly what has been achieved by the team building Campus East Gateway: a partnership between funder Equitix and design-and-build contractor Graham, with architect Sheppard Robson and precast supplier FP McCann. “This was – is – a design, build, finance and operate contract,” says Neil McFarlane, special projects director for Graham.
“If anything went wrong with quality or programme, it would be us who would suffer. So when we looked at the various construction methods and materials we could use, we were thinking about the tight programme, and about risk. And the more we thought about the speed of construction, cost certainty, quality control, compliance, and low ongoing maintenance, the more obvious it became that MMC [modern methods of construction] using precast was the way to go.”
Of course, back when the project was in the planning stages, Covid was not one of the risks that McFarlane envisaged: “But the precast solution turned out to be a hidden gem in our risk management strategy,” he says. “The system of off-site prefabrication and rapid assembly proved extremely resilient. We barely stopped.” In practice, this meant McCann delivering panels on a just-in-time basis to be lifted into position by one of the two cranes on site.
“Each crane had a team of just ten men and, being crawler cranes, they could work on more than one block at once,” says McFarlane. “It took around eight weeks to complete a block and we were working on up to four blocks at a time. It was so fast we were completing the enclosure of each room in an average of 1.9 hours.” This pace allowed the team to deliver 300 rooms a full two terms ahead of schedule.
Situated in a peaceful lakeside location, Campus East Gateway is today a calm and stylish neighbourhood, the first phase of which has just been recognised with a 2023 RIBA Yorkshire Award. The materials palette includes brick and steel, but concrete is predominant, echoing the more brutalist character of York’s 1960s-built Campus West. “Part of the brief was to create ‘Yorkness’,” says Natalia Maximova, associate partner with Sheppard Robson, and RIBA Yorkshire Project Architect of the Year.
“By this, the client was not talking about old York, rather the character of the existing York campus. So while programme and risk were deciding factors for Graham, the decision to go with concrete was a great opportunity for us to replicate some of the design language of Campus West.” This included its panels of concrete artwork by artist Fred Millett.
Each block at East Gateway is constructed almost entirely from FP McCann’s precast panels (see box, page 26). The facades are made from insulated 465mm-thick sandwich panels, while slimmer 160-180mm panels form the internal walls. Each room is completed with a 175mm-thick precast slab or “lid” which cantilevers beyond the room perimeter to form half the ceiling for the internal corridor.
The wall panels for the room above are attached directly to this slab. “Being a crosswall system, the walls are part of the structure,” explains Maximova. “FP McCann joined the team very early in the process, and it helped that we could design from the start with the manufacturer's systems in mind. Having substantial concrete walls to every room means that they perform very well acoustically – you really can’t hear much from next door. It also meant that we exceeded the requirements for fire rating.”
Although the rooms do feature some plasterboard around the en-suite bathrooms, most of the walls are plasterboard-free and the rooms have no false floors or ceilings. “The concrete wall and ceiling panels are so smooth that they just need painting,” she says. “This keeps things simple. Risk is reduced by having fewer materials and fewer trades on site – and that really helped during the pandemic.”
This approach did mean that services conduits had to be carefully worked out early in the design process, and cast into the panels. “"The rooms are arranged so the student desks are situated symmetrically on either side of dividing walls," says Maximova. "We discovered that the panels could not accommodate conduits for two desks, if arranged directly opposite, and the acoustic performance was compromised, so we changed the layout to offset the services. You only find out these things by doing them.”
The slim structure delivered a further important benefit: although the floor-to-ceiling height is 2,525mm, the lack of false floors or ceilings means the floor-to-floor height is only 2,700mm. “Planning restrictions limited the height we could build to, but this system allowed us to fit four floors in more of the blocks and provide over 200 rooms more than were envisaged in the original brief.”
An additional advantage to this “structure- as-finish” approach is that it helps to regulate internal temperatures. “It’s not that unusual these days to have an exposed concrete soffit to benefit from the thermal mass of concrete,” says Maximova. “But our blocks have exposed walls as well – lots of them – so the thermal mass effect is especially significant.”
The buildings are naturally ventilated with user-operated windows that open inwards to allow a considerable flow of air. In summer, this allows the concrete to cool overnight, ready to absorb heat from the spaces the following day. Conversely, in winter with the windows shut, the concrete becomes a store of warmth, thus reducing the need for heating.
The blocks also benefit from a high degree of airtightness, due to the fine tolerances to which the precast panels are manufactured, and the close fit that results. This helps preserve the “storage-heater” effect of the concrete’s thermal mass. “We were achieving airtightness close to Passivhaus. Combined with a considerable thermal mass, it resulted in energy-efficient sustainable buildings: after the first year of use, the energy use is significantly lower than the predicted level.”
The passive temperature control offered by the thermal mass means each room has just a small electric heater, and the blocks need no active air-conditioning or mechanical air supply. “This cut down the M&E services – again keeping things quick, simple, and reducing the need for labour on site.” Outside, the architectural dialogue with the original 1960s campus is clear to see.
A typical facade sandwich panel, for example, comes complete with windows, brick panelling and, above the brickwork, what appears to be a concrete crossbeam. Rows of such panels, one on top of another, give the impression of exposed concrete beams or floor slabs, though the concrete in question is entirely non-structural, being merely part of the external skin of the sandwich panel.
But perhaps the most significant nod to the original mid-century styling are the patterned precast art panels that Maximova designed herself. An artist as well as an architect, Maximova became fascinated by the history behind the Fred Millett panels which can still be seen in Campus West. “Fred died in 1980, but I became so interested in his work. I was able to contact his daughter who remembers the moulds for the York panels being constructed in the family’s garden. The precast company that made them, Evans Bros [now Evans Concrete], is still operating.”
‘The key to efficiency is repetition’
To create the 18 accommodation blocks at York, FP McCann provided 7,177 individual precast units including walls, floor slabs and external architectural sandwich panels. Because of the scale of the contract, panels were supplied from three facilities: Byley, Littleport and Grantham.
”We had to be careful to maintain a consistent colour and appearance across the three sites,” says Gavin Lowe, structural and architectural precast manager with FP McCann. “But we batch our own concrete and this was a fairly standard mix, so we had few problems with that.”
The mix contained about 30% fly ash (FA) to lower the carbon content: “It also helps provide the smooth, consistent appearance required when the panels are simply going to be painted as an internal finish. It helps too that our mix is self-compacting.”
The larger facade elements weigh 10 tonnes and are 2.7m high and two rooms long – or just over 6m. These insulated sandwich panels comprise a 150mm-thick structural concrete inner skin designed to carry its own dead loading and that of the external skin. Added to this is a 200mm layer of insulation and a 115mm outer cladding of concrete, in many cases with cast-in brick panels.
“These are made on steel tables onto which we place a CNC-cut timber form with precision-cut indents for the position of each brick,” explains Lowe. “Most of the bricks are cut in half, and we use both halves, placing them face down in the mould. Some designs featured projecting bricks and so, for those, we used whole bricks. We then place removable strips between the bricks and cover with a little dry sand to prevent concrete leaking through to the visible brick faces.”
The bricks are covered with steel mesh before the first layer of concrete was poured. Then, while the concrete is still soft, the insulation is added on top and fibre-reinforced resin pins with low thermal conductivity are pushed through to bond it to the cladding. Some of each pin is left projecting – so when the rebar and concrete is added to form the structural inner layer, this too is bonded to the insulation. Once de-moulded these external panels are finished with a light acid etch.
Simpler to make were the uninsulated internal panels, typically weighing seven tonnes. The ceiling slabs were simply cast flat, and with most spans only 3m long, or the width of a room, there was no need to prestress them. The internal wall panels were made in the same way. “With a job like this, the key to efficiency is repetition,” says Lowe. “So we worked hard on the design of the wall panels to ensure that, as far as possible, they all had the same conduit set cast in.”
FP McCann also supplied precast pillars to support the blocks’ overhang “porches”, and precast staircases. In all, the contract lasted 56 weeks – a significant time saving on the original estimate of 18 months.
A key difference between Millett’s work and the new designs is that while he made a few one- offs, Maximova had to design for mass production. “There are three different designs: one quite placid, inspired by the stillness of the lake, one more active, like the light filtering through moving leaves, and a third featuring sawtooth designs. Each design includes three depths – 50mm, 80mm and 120mm – not as deep as Fred’s, but enough to cast distinctive shadows. Any deeper would risk water retention and excessive staining.”
These panels, a floor high and up to 5m in length, were manufactured by FP McCann using a proprietary “architectural mix” and bespoke flexible form liners. “The trick was to stop the design becoming boring through repetition, so roughly half the panels are cast with the form liner rotated 180°,” says Maximova. “The patterns looks quite different that way. We also needed different sizes, so each design has a place where the panel can be safely cut without eating into the indented designs and creating fragile edges.”
Changing the size, orientation and using the three different designs in different ways throughout the blocks creates a surprising amount of variety from just three mould shapes: “People tend to think there are more than just three designs." So did the MMC approach work for the architect? “It does mean a longer upfront preparation period to sort out the design in detail,” she says. “But once on site it’s exceptionally quick and reliable. As for crosswall construction, you couldn’t use it everywhere – we looked at it for a hospital, but the length and variety of spans involved made it unsuitable. But for projects like student accommodation, or hotels, it’s a very practical, high- quality solution.”