Contractor brings in its category A subcontractors for a building that will be the new face of Kingston University.
Project: Kingston University Town House
Client: Kingston University
Contract value: £41.3m
Contract type: JCT Design and build
Main contractor: Willmott Dixon
Architect: Grafton Architects
Concrete frame subcontractor: PCE
Start date: April 2017
Completion date: April 2019
Walk north from Surbiton station toward Kingston-upon-Thames and it’s hard to miss Kingston University’s Penrhyn Road campus.
It is marked by two tower cranes that soar over the five-storey flat grey concrete frame of its latest addition: the Town House.
While still a way off completion, this new building will become the focal point of Penrhyn Road, the university’s main site – a sort of front door to welcome students and staff.
Of course, this landmark building will be rather more than just a front door. It will feature dance and creative arts spaces, a performance auditorium, library and resource services, as well as cafes, breakout spaces and study areas.
The Town House will replace a rather dated low-rise building that offered limited facilities and was well beyond its sell-by date, as Kingston University Estates technical co-ordinator Gary Young concedes.
“There was a two-storey building that had been here since the early 1980s,” he says. “It only offered around 3,000 sq m of space. The new Town House will give us three times that at 9,000 sq m, and from a similar footprint.”
Main contractor Willmott Dixon has been appointed to deliver the build for Kingston University under a £41.3m JCT design-and-build contract.
Senior operations manager Tony Mingoia is looking after the project team for Willmott Dixon and is focused on delivering the facility ready for its 2019 deadline and the influx of new students.
“The contract was awarded in December 2016 and we eventually got onto site in April 2017,” Mr Mingoia says. “There was demolition work that needed to be carried out first, and we needed to really get the structural design of the building worked out.”
The university had put the design of the Town House through a RIBA competition, with architectural practice Grafton Architects’ ideas getting the nod. “It is a very open design, despite its small footprint,” Mr Young says. “There are lots of open spaces and high ceilings that convey that sense of space.”
BIM benefits project and students
Willmott Dixon is one company that has embraced the BIM revolution, taking it on and pushing its use through to its supply chain. Mr Mingoia says subcontractors have responded well to this drive, particularly on the Town House.
“We have been lucky,” he says. “Our supply chain has really seen the benefit of BIM and has embraced it. This project is BIM Level 2 and would have been incredibly difficult to carry out if we didn’t have suppliers that bought into it.”
With fortnightly design meetings between precast frame supplier PCE and mechanical and electrical specialists DES Group and CMB Engineering, the team was able to incorporate the completed M&E design within the frame design immediately. Fortnightly clash detection meetings have continued throughout the job.
“We wanted the project to be a full BIM Level 2 scheme,” Mr Young says. “Once again it points to the project being a trailblazer for the industry and for buildings of this type. It has been a fantastic resource for our structural engineering students because of that. They are able to see the quality of building that a precast concrete structure can deliver.”
That feeling is also partially due to the completely exposed surfaces of the precast concrete frame. In the new Town House, the exposed concrete is everywhere; there are no surface fixings. Walk onto the site now and what you see will be – with the exception of a dust-supressing coating on the concrete surfaces, glazing and the odd bit of balustrading – what those first students will see upon its completion.
Achieving a perfect finish
Leaving the structural frame open to such close scrutiny means the surface finish needs to be absolutely spot on. There can’t be any blemishes or air pockets showing to ruin the sleek finish. This finished surface quality was one of the reasons the team went down the route of using precast concrete rather than cast in-situ reinforced concrete.
“Initially we looked at how best we could work around the design,” Mr Mingoia says. “There are a lot of constraints on this site: it is quite a small plot; it is difficult to work on; there are certain design requirements. We recognised quite early on that using precast concrete was the best way forward for the frame.”
The Willmott Dixon team called on its category A firms from its supply chain list, with Tamworth-based concrete and precast specialist PCE accepting the challenge to deliver the structural frame.
“The goodwill of our neighbours and the speed of erection on site were much more attractive benefits of the precast solution”
Gary Young, Kingston University Estates
Normally one of the factors that helps sway the decision to use precast concrete is the amount of repetition through the design. Conventional wisdom dictates that the more there is, the more attractive a precast solution becomes for the structural frame (see box).
But at Kingston University there is very little repetition. Ductwork for services, pipes, cables and communications are cast within each structural member. There are barely two sections the same. “It wasn’t a consideration for us,” Mr Young says. “The goodwill of our neighbours and the speed of erection on site were much more attractive benefits of the precast solution.”
When not to pile
Despite the weight of the frame, the building is founded on a reinforced concrete ground-bearing slab which varies in depth from 1 m to 2.5 m at the crane bases. The team did look at piling the foundations, but the required pile dimensions forced a rethink.
Back to the traditional
There is, however, one section of the building that is traditional. Despite all the precast concrete frame, colonnade, stairs and slabs, the architects still wanted a traditional hand-laid, full brick finish to the cladding panels installed across the exterior elevations.
These small infill sections give an architectural nod to the surrounding buildings and the designs wanted the finish to be in keeping with the rest of the local building stock.
Bricklayers will use the precast colonnades as working platforms when hand-laying the panels.
“There are sections of Portland Stone cladding which were designed to be in keeping with Surrey County Hall, and the brickwork ties in with other university buildings,” Mr Young says. “We didn’t want the uniformity that a precast panels and brick slips system gives. It is not what you would normally expect on a job so dependent on precast concrete, but we wanted to have the hand-laid look.”
“It just didn’t work out,” Mr Mingoia recalls. “The size of the piles and the difficulty of working on the site without disturbing residents, or the day-to-day working of the university, just made it a more complicated solution than it needed to be.”
Outside the main structural frame there is a precast concrete ‘colonnade’ that wraps around the Town House’s north, south and western elevations. This will double as a working platform for the teams installing the glazing and curtain walling as well as the bricklayers that will hand-lay the traditional brick cladding inserts (see box). Traditional scaffolding will be erected on the eastern elevation where there is no colonnade.
“The colonnade is around 5 m deep and will provide some solar shading, which is important, particularly on the south elevation,” Mr Mingoia explains. “The curtain walling is complicated too – there is lots of it.”
The completed building will aiming for a BREEAM Excellent rating for its sustainability, a contractual requirement that puts the Town House in line with other newly built additions to the university’s estate. A photovoltaic array, large SUDS system, underfloor heating system, the frame’s own thermal mass as well as green roofs and roof gardens help it meet that exacting standard.
“It is very important to us that we hit those high environmental standards both in the construction and the operation of the building,” Mr Young says. “We want the Town House to be an exemplar for others to follow.”
Next year’s Kingston University undergraduates certainly have a lot to look forward to.
Call the A-Team
There are normally a few checkpoints that make a precast concrete frame a more desirable option.
Manufacturers will usually call for repetition throughout the frame with a limited number of changes in the shape and size of the different elements, while developers and clients will look toward the speed of construction and quality of finish.
Conventional wisdom dictates that the less repetition within a design, the more complicated it is to precast, negating any productivity and financial advantage that may have been gained.
At the Town House, it was the Willmott Dixon team that urged the client to go down the precast route. This was despite the fact that complicated service channels and ductwork needed to be cast through each element, thus ensuring barely any repetition at all throughout the frame and 1,843 precast concrete components across the project.
“There are very few pieces that are identical,” Mr Mingoia says. “The hidden services play their part and the variance throughout the frame means that most of the column and beam junctions are individual.”
Despite the frame’s complexity, he says that being able to call in one of Willmott’s category A specialists from its supply chain has paid dividends.
“We are able to have the early conversation with our suppliers and make sure that everything in the design is catered for,” he says. “We can position fixings and ducts – even lifting points – at a very early stage. It means that when we get to site there shouldn’t be any problem. True enough, the frame has gone up very quickly.”
Some of the precast concrete beams span up to 12 m, with the bulk of them 500 mm deep. The largest are 750 mm deep and weigh as much as 22 tonnes. All are lifted into position directly from the delivery wagon, which pulls into a lifting area alongside the main structure.
The floor slabs are of composite construction, with a ‘Twin T’ 50 mm-thick and 2 m-wide plank that houses the wet underfloor heating system fixed in place before concrete is poured to bring it up to full slab depth.