Second sight

1 - Winton School, Islington

Winton Primary in Islington, north London, is like many an inner-city Victorian school in that it is on a cramped site with little room to expand. So when the school needed a new sports hall, the only way was up: they built it on top of a single storey classroom building.

James Pickard, director of architect Cartwright Pickard, explains: “We were commissioned to prepare a masterplan for the area, which included the school and adjacent land that had been sold for a modular housing scheme. The school had an existing ball court on top of one of the buildings and it was the only place to put the new hall.”

From the start, Cartwright Pickard decided that off-site manufacturing was the best option. Richard Pickard says: “We had to minimise the impact of construction on the school, and we had very little space on the site to store materials.”

He adds that other major concerns were the inherent health and safety risks associated with building on a very restricted site above, and surrounded by, 300 inquisitive youngsters.

“prefabrication was the safest and most practical solution and a panelised system was the most suitable.”

Disruption to school was also minimised by the residual strength of the Victorian building on which the 20 m × 10 m double-storey sports hall was to be placed. Pickard reports that some underpinning was necessary to increase the load-bearing capacity of the foundations of the existing walls. A structural steel ring beam was also fixed on to the existing roof to transfer the load of the new hall down through the existing walls to the newly strengthened foundations.

Steelmaker Corus carried out the detailed design for a steel framed roof and wall panel system, working from the architect’s outline design. Working on the £750,000 project in a joint venture with main contractor Bluestone, Corus assembled the panels under factory conditions in Norfolk. Before their dispatch to London, a trial erection ensured all the panels fitted accurately together. Panels were delivered fully lined and insulated, with only the need to fix some areas of the western red cedar external cladding once on site.

The wooden theme was continued with the use of high quality plywood to line the internal walls to a height of 2.5 m. An ancillary block contains changing rooms, toilets, storage facilities for sports equipment and a kitchen as well as a lift and staircase. The lift and stairs provide separate access for local community groups, which use the hall outside school hours, but are prevented from gaining access to the rest of the building. Providing facilities for the local community was a prerequisite to obtaining funding for the scheme from Sport England under its Space for Sports and Arts initiative.

“The project was very successful and gave us few problems or issues,” reports James Pickard. “It was finished on time and within budget. And the school is very pleased with the end product.”

The only thing that rankles Pickard is that the ancillary block is not clad in cementitious boards, as originally specified. Foam-filled aluminium cladding panels were used instead after value engineering cut costs.

What next

Winton School was such an unusual project and tackled in such an innovative and effective way that Cartwright Pickard believes it would do little differently if the practice was called up on do a similar scheme tomorrow. Project architect Claire Robertson says: “A panelised system was the best solution, but we had to use scaffolding when bolting the panels together. I wanted to see the building designed to avoid it.”

Pickard adds: “We now have that: a building on site where we have designed out scaffolding by carefully choosing which prefabricated structural and prefabricated cladding systems to use. Scaffolding is a costly and dangerous activity, so the more you can do to avoid it, the better.”

End-user’s report

Although the sports hall has been in service for just over two years, it is showing commendably few signs of wear and tear. Apart from the pupils, the hall is used by local groups at least four nights during the week and often at weekends. Activities include badminton, karate, aerobics and basketball. “We’ve had no problems to speak of regarding repairs and maintenance,” says caretaker Bill Graham. “The only trouble was with one door lock.”

2 Shepton Mallet NHS treatment centre, Somerset

By any standards, Shepton Mallet NHS treatment centre was built remarkably quickly. Only 10 months after off-site manufacturer Yorkon received the go-ahead for construction, the £12m centre was ready to receive its first patients.

The project is the first independent sector treatment centre to be built using off-site construction, although the original intention was for a traditional building. But the loss of revenue that operator UK Specialist Hospitals would have suffered had it missed its contractual start date for treating patients of July 2005 led the project management and design teams at Atkins to go for prefabrication.

Detailed design by Atkins and Yorkon took almost five months to finalise, which dovetailed with obtaining full planning consent. The 4000 m²two-storey building was formed from 96 modules, based on unit size of 14.2 m long by 3.3 m wide, laid on simple-to-construct pad footings. The steel-framed modules are designed to give a clear span of 12 m, which allows flexible planning of the internal layout as walls are non-load bearing so can be sited almost anywhere. Yorkon director and general manager Keith Blanshard says the average fabrication time for each module was around 10 days.

“We believe it is the most complex modular building ever constructed,” says Yorkon project manager Rebecca Thompson. “So you always have to be thinking ahead.”

Insurers like the concept because any water leaks can’t spread into the flats below

The only reported difficulty was getting the utility companies to install the services on the agreed dates. “You have to hassle them,” Blanshard remarks, “but doesn’t everyone have a problem with utility companies?”

What next

Yorkon has developed a module that enables designers to avoid simple square or rectilinear-shaped buildings. The modules have a facet of 10 degrees that, arranged side by side, create a curved façade. And the company is developing a system for six-storey buildings with open plan modules offering 12 m clear spans. It should be available next year and is targeted primarily at the education and healthcare markets.

End-user report

Glenys Mansfield, registered manager at the centre, has little to fault with the building. The centre can carry out 12,000 operations per year such as knee and hip replacements, cataract operations and general surgery. Mansfield says the layout of the building has a very good “flow path” for patients to progress from reception through the various stages of treatment such as consultation rooms; diagnostic rooms with X-ray, ultrasound and MRI scanners; before finally entering one of the four operating theatres.

She says: “When I first came here, I didn’t realise it was a modular construction. There is nothing to distinguish it from a normal building, except perhaps it is very easy to keep clean.” The only slight niggle is storage space. “You can never have enough,” says Mansfield. Patients seem to like the building as well. On discharge, patients are asked if they would recommend the building and their treatment to others. Over the past three months, the approval rating has been 100%.

3 Baron’s Place, Waterloo

Tucked around the back of London’s Old Vic theatre is a small housing scheme that is helping push back the boundaries in off-site manufacturing. The six-flat Baron’s Place development was conceived by housing provider Peabody Trust and agency Keep London Working as an affordable rent solution for housing key workers.

The NHS alone has about 60,000 staff around the country wanting places to live which are not student-style cluster apartments with shared facilities like kitchens and bathrooms.

To achieve the objective of being able to offer a 36 m² single occupancy apartment for a rent of around £85 per week, the scheme had to be built for about £1100/m².

Peabody and Keep London Working appointed fledgling housing specialist Spaceover to help develop the concept in accordance with the key requirements of meeting cost constraints and ensuring housing modules could be easily relocated, to allow use of land that would be available only for a few years.

Baron’s Place was built of 15 modules measuring either 3.6 m × 5 m or 3.6 m × 7 m, with all the units craned into position over a single weekend. It comprises three, single-person flats and three, 54 m², two-person shared apartments. In these both sharers have their own entrance door, shower room and bedroom, with the communal kitchen and lounge area sandwiched between. The ground floor of the three-storey building is being used by Spaceover as show flats, which have attracted more than 5000 visitors. Total build time was around seven months, with the first residents moving in during September 2004.

The project is unusual in that Spaceover acted like a management contractor. It employed Proctor and Matthews as architect; Ayrshire Metal to make the modules’ metal frames; Rollalong to fully assemble the units; and Clancy Docwra as general contractor.

All the services for the apartments are contained within ducts that can be reached without entering the building, which means any maintenance or repair work can be undertaken while residents are at work. Steve Barrett,

co-founder of Spaceover, says the acoustic and thermal performance of the modules better the current Building Regulations by around 15%. The system was the first to receive LPS 2020 accreditation – the standard for innovative methods of dwelling construction – and Barrett says the system is “mortgageable and insurable”.

He explains: “Insurers like the concept because any water leaks can’t spread into the flats below. The modules are rigid and their load is uniformly distributed, so they can stand up to a fair degree of subsidence of the foundations. And because we use dry building techniques, there is none of the shrinkage that you get with the wet trades and no need for coving to hide any cracks.”

Where next

Since Baron’s Place, Barrett says Spaceover has received a lot of interest from a mix of prospective clients from NHS trusts to private developers and from housing associations and registered social landlords. The company has projects worth £11m on site. So far, the Spaceover system has only gone as high as four storeys, although Barrett says the modules, which are fabricated from fully welded galvanised steel, are suitable for up to 10 storeys.

The company says that one of the biggest challenges is finding ways to work more closely with utility providers. Although many housing projects suffer from delays in getting the service connected, the problem is exacerbated with

off-site manufacturing because of the speed of construction. Barrett says architects are beginning to appreciate that OSM “doesn’t mean you have to have a rectilinear box”. He adds: “Because we use a fully welded system, you can have modules of almost any shape – one with semicircular ends or like a wedge of cheese.”

End-user assessment

David Gregory worked on the project for Keep London Working. “It is quite an exceptional building and was designed with two key things in mind,” he says. “First, the modules had to be built as rigid boxes to take the stresses if they were ever moved to another site. Second, the services had to be accessible and unpluggable so there would be a minimal amount of work to do if the building was relocated.”

Peabody says involvement with Spaceover well before planning permission was sought allowed for more accurate cost forecasting. The trust says it learned that the short construction period means any design or planning issues must be resolved before work starts on site. At Baron’s Place, unresolved problems involving construction of the staircase, security gate and landscaping delayed completion by a few weeks. Few faults were noticed either during construction or in the subsequent defects period and all were easily rectified, Peabody reports.