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Specifier's choice: Students' union building, Southampton

Tim Coel of Perkins Ogden talks to Sutherland Lyall about converting an iconic building into new uses, and ensuring it was robust enough to withstand the antics of drunken students

The Basil Spence-designed students' union building at the University of Southampton is a steel, glass and concrete structure, whose four blocks cascade modestly down a very steep slope. The university originally commissioned architect Perkins Ogden to carry out a very small feasibility study - the founding partners are former Hampshire architects and have built a reputation for education work. But with a waxing and (mostly) waning budget and a disparate client body made up of a lot of student organisations, the small feasibility study developed into a big one. Eventually, says project architect Tim Coel, 'we came to the abridged-abridged version'. This was agreed and Perkins Ogden found itself having to tender for the architectural commission.

Happily, it won.

The four separate rectangular blocks of the existing union building are connected by a north-south circulation route, which runs down from the lateral block at the north and exits at three levels between the two south blocks. One of these is the main sports hall, the other is a group of squash courts. The physical and visual link between the sportshall mass and the north block was a square debating chamber. On the other side of the central route was a freestanding squash court, with access, as to the other squash courts, from a level below. Main entrance was via the top block, running east-west, with access to the refectory on the floor below - and offices on the floor below, half buried in the slope.

The new work involved the refurbishment of the existing spaces and conversion of one of the squash courts into WCs. The major change was the conversion of the debating chamber into a multi-purpose entertainment facility. Work concentrated on the insertion of a glazed link between the top and bottom of the site; an enlargement of the old open circulation route and its transformation into a two-level foyer with bars on each level serving the new entertainment space.

Coel says: 'What was unusual was that there were two main staircases, which meant that whichever way you went you were confused. I'd like to think that the scheme we have done is what Sir Basil would have done if he had had a bit more money.'

Designers and clients The university appointed the individual members of the design team - an increasingly common and seemingly necessary consequence of the spread of fee bidding. It can be a shotgun marriage, but it seems to have worked well enough here. As Coel says: 'We had worked with the surveyors and the engineer before and we were very lucky that the engineer we got was very good.' Formally described as project manager, Perkins Ogden gave project manager instructions but effectively had the traditional architect's role.

The client body included students. Coel says: 'We were lucky that the entertainment bloke, a postgraduate student, was brilliant.

He went off to trade shows, had demonstrations of all the lighting and sound systems staged and attended all the meetings. He bought all the lighting on behalf of the union.

Similarly, the union film people were hugely proactive and we had consultations with them so their equipment would integrate with our installations. They were all brilliant. And they now have an awesome sound system.'

Starting up running Coel explains the early stages of the project:

'It was tight. We had gone through so many variations of the schemes and had to get on site in a few months because we had to get it done in a year. So we didn't have time to vet a project manager. That also meant they decided to go through a two-stage process for the main contract. They put out tenders on the basis of negotiated prices, plus a fee for pre-contract advice.

'Once we had Bluestone on board it was a partnership, and once the full set of drawings had been completed, it was a process of open-book price negotiation. It got us going quickly. It also allowed us to do the enabling work on the services on site while we were negotiating. We had our ups and downs, but to a large extent we were working together;

Bluestone is promoting the partnering idea and did work well. We got a lot out of their expertise and they saved us money on some sections, thus releasing it for others.'

The safeguards are that negotiating the contract price is an open-book process.

Overheads and profits had been tendered as fixed-lump sums. Crucially, a reduction in base construction costs results in an increase in the contractor's general fee.

Fans of Macs Perkins Ogden has used Macs from the beginning; it currently runs OS9 and used version 8.5 of VectorWorks for Southampton. Coel had come from an AutoCAD office but found VectorWorks (in earlier incarnations known as MiniCad) much friendlier. It even inspired him to upgrade his home PC to a Mac.

'VectorWorks is simple and not as complicated as AutoCAD, ' he says. 'It's more than adequate for our work - we use maybe 10 per cent of its capabilities. I think it gives a more consistent set of drawings.' VectorWorks can output AutoCAD-friendly DWG files and integrates well with Artlantis, the package the practice uses for 3D rendering. A compelling argument for VectorWorks is the cost - with ArtLantis it is still less than £1,000 per seat.

Unusual contract The project used a PC/Works (1998) contract - a form based on the government contract devised in collaboration with the Construction Clients' Forum. Coel says: 'We had heard of it, though not used it, but our quantity surveyors, Northcroft, recommended it. We had to modify our instructions and valuation forms but the process was pretty much the same as JCT.'

Happily nobody had cause during the job to make recourse to the contract. 'We had no gripes with it, ' says Coel. 'We had done a comparison with JCT, which showed that it was simpler, more comprehensible, less complex and less biased against the employer.' The contract went a little over budget and an extension of time was given for early unexpected complications, but everyone seems to have been happy with the result.

The complications included asbestos, major cabling runs embedded in slabs and the discovery of a former crane base, which Coel describes as 'an enormous bit of concrete right where we wanted to put the piles'.

Although the contract was mildly unusual, the architectural team stayed with the National Building Specification (NBS), which enables architects to specify products by name, or a satisfactory equivalent. Perkins Ogden normally specifies British Gypsum and did so here; it has Dulux written into its standard NBS paint clauses; and it almost always specifies Humphrey Stretton doors - here with Phillip Watts Design 60mm wide stainless-steel framed vision panels.

The 'or equal' proviso in NBS was exercised occasionally. 'As a cost saving, the Custom beer-keg and provisions lift was substituted for the one we specified, ' says Coel. 'And the stainless steel WC cubicle system and vanity tops were substituted by the contractor with a laminate system from Maxwood. It works well and is economical.

Stainless steel, it's true, is difficult to clean.'

The main structural item was the steel frame of the link building by Hawk Engineering and Construction, with a composite steel profile, ply warm roof, steel profile and concrete floors from Composite Profiles.

Converting the old debating chamber into a multi-purpose entertainment space involved installing concrete planks with built-in lenses, supported by dwarf brick walls laid along the old stepped concrete seating tiers. There was also about 150m 2of new brickwork, which Ibstock was asked to match with the old.

Acoustic roof The roof over the new entertainment space had to be insulated acoustically with precast concrete planks from Hanson Birchwood, this time without lenses and supported on 1m deep I-beams across the space. The standard single-skin, warm-roof membrane is from Protan and was laid by roofing subcontractor Roofing (Euro). 'We specified Sarna, ' says Coel, 'but the contractor came back with a cost-saving plan based on Protan. We went through the process of verification and it seemed very good - it helped out a lot.'

In the ceiling of the link are four big multi-bladed roof fans. Coel says: 'In early M&E meetings we came up with the idea of the big fans and eventually they became part of the design. CE-Air International developed fans with 4m diameter blades, which work at the very baseline of their capability, whirling around at 300 revs instead of 2,000.'

The fans rotate in squat plasterboard ducts cut into the link's ceiling and hung from the steel frame of the roof. They are controlled by a building management system, in which heat is reclaimed back into the local districtheating system. From outside, these are enclosed by square boxes with sloping glass patent-glazing lids from Duplas Architectural Systems, a company Perkins Ogden had used before. There are hidden neon lights to enhance the drama.

Link, light and shade The great west curtain wall to the link is Trame Horizontale from Technal, installed here by Solaglas Architectural Systems. It has mullions but the transoms are mastic joints, so that the glass reads as vertical strips. Above the ground-floor level, the mullions have cedar brise soleil from Levolux attached to them.

'They were one of those things that turn up one day and they just look lovely, ' says Coel.

'Levolux does a lot of standard stuff but it does bespoke as well and we went through a lot of design work to get them right.'

At ground level there is direct access to the newly decked courtyard though frameless sliding glass doors from Alco Beldan. 'At 3m, they are at the absolute maximum of their recommended height, ' explains Coel.

'And they are absolutely brilliant. Because they are frameless, there is a 3-4mm gap between glass leaves but there hasn't been an issue with loss of heat. We made sure to ask the client about taking the risk of a frameless system but it went in very well and there seem to be no problems.'

The corner of the new WC block, a converted squash court, sticks out into the southwest corner of the link and is wrapped in AME insulated-steel cladding. Coel says: 'We liked it because it's very flat and has equal horizontal and vertical joints, with a flat rubber seal, so it all looks like one lump. It was difficult to get details out of AME and we thought it was going to be troublesome because of the junctions, but two guys from the fixing contractor, ICS, came on site and it turned out very well.

Hot spot The new multi-purpose space has a balcony at one end, which is the upper-level exit for the retractable seating and also provides a base for the elevated projection booth. The original shuttered concrete had been repainted repeatedly. The architect chose Keim concrete paint to mimic cast concrete, and elsewhere used a Eureco sealer on exposed concrete.

Underfoot The concrete planking has built-in circular lenses, although it was difficult to get assurances about the durability of the glass with people stamping on them. There are bluegelled fluorescent lights mounted on each side of the dwarf walls supporting the floor, which pulsate in time with music. The floor surface is Armorex - concrete that has had metal powder sprinkled on its still-wet surface, which is subsequently floated and polished.

Soft room Because most of the surfaces are very hard, there was a need for acoustic attenuation, especially when the space is in its cinema configuration. So every surface above a height of 2.4m is coated in 50-100mm of Cousti Foam from Sound Reduction Systems. On vertical surfaces this is faced with a mesh of galvanised steel from Thielco Grating, bolted back through the foam to the mainly blockwork walls. The mesh has the dual function of being a stylish visual surface and also preventing students from picking away at the foam. The cinema screen was an expensive item and, as it was feared students might throw beer cans at it when in its rave incarnation, it is protected by a retractable screen from Crawford HAFA.

Quick change The electrically operated retractable seating is by Audience Systems. 'The seating system was very complex, ' says Coel. 'Audience Systems had come up with the system in a job it had previously done for Granada.' The seats and the floors are concertinaed into a column the width of the room and held at the back wall under the balcony. 'When they are needed they slide out to the edge of the balcony on floor tracks. The whole thing is then concertinaed out and the seats are flicked down. It's truly flexible - it takes about 15 minutes to convert the space from an auditorium to an events space. Because it is stored in a smoky environment we had overlapping fascia panels made up, which form a near-seal in front of the seating.' There is also a duct at high level behind the seating to produce positive air pressure to keep smoke at bay.

Safety first The entrance at the upper level of the transverse north block leads to the top of the big staircase in the glass link. The link is a fire compartment but Coel wanted to keep the junction as fluid as possible, so fire control agreed to substitute fire doors at the head of the stair with a roller fire screen (people can push it through in an emergency) from Cooper Group, which drops down at an alarm and can be reset quickly. Nullifire intumescent paint was applied to the steelwork by Elite Fire Protection. Gable supplied the man-safe roof equipment, and the internal cleaning cradle for the glass wall to the link is by South West Cradles. The outside glass is cleaned using ladders and a spray of water.

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