Hidden treasure

If bold architectural statements are what great buildings are all about then it’s safe to say that the architects had a real challenge when designing the new extension to the Ashmolean Museum in Oxford. Hemmed in on three sides and hidden behind an existing 1845 neo-classical frontage, the building has no visible elevations, and its 39 new galleries had to be squashed into just five storeys over a 10,000m2 footprint.

But thanks to the clever manipulation of interior space and light, and some ingenious construction techniques implemented by main contractor HBG Construction, there’s actually a great deal more to this museum than first meets the eye.

When it was opened in 1683, the Ashmolean was the world’s first public museum, heralded as a beacon of learning for a new scientific age, housing art and archaeology of great national and international importance. Over the centuries the museum expanded: a Greek revival structure was built by Charles Cockerell in 1845 – subsequently grade I listed – and this was supplemented by new courtyards and blocks to the rear as departments grew.

There was little co-ordination of the overall design, as Ashmolean special projects manager Roger Hobby explains: ‘The way it had been built up was very wasteful of space and subsequent attempts to make it more efficient had simply divided it into an incoherent mass of boxes. By the 1990s it looked like a shantytown from the back and the structure was no longer producing the appropriate environmental conditions for a museum.’

Unsure of how to proceed, in the late 1990s the museum’s owner, Oxford University, asked London-based Rick Mather Architects to devise a solution. Controversially, Mather recommended ripping everything out, apart from the Cockerell building to the south, and starting from scratch.

‘Although drastic, the rebuilding meant we could take a completely fresh approach to how the museum’s collections are being displayed,’ says Hobby, who is acting as liaison between the museum and the site. ‘Other museums may improve or refurbish from time to time but few can reinvent themselves almost from scratch.’

Arranged over five floors the new Ashmolean will provide 100% more display space than before, which means many objects that have been kept in storage can now be displayed, while new environmental controls will allow the rarest and most fragile items to be exhibited. A separate six-storey education centre and administration building, accessed via a side entrance, will sit at the rear, offering new research facilities and community use, while a steel and glass rooftop restaurant provides picturesque views across Oxford.

Another useful addition is pedestrian access to the cast gallery, which houses one of the oldest collections of casts of Greek and Roman sculpture in the UK and was previously only accessible via a separate street entrance.

The confined site presented many challenges. ‘Because there’s literally no room for expansion when the building’s finished, everyone’s under considerable pressure to get things right first time,’ says HBG project manager Tony O’Keefe. ‘For example, we’ve had to install grade 4 waterproofing on the lower ground floor in case of future flooding, however unlikely. It’s not something you can go back in and do at a later date.’

When it came to constructing Ashmolean, much like a ship in a bottle the whole museum had to be assembled via a tiny 3.8m wide passage at the rear of the site. ‘The tight site and planning issues forced us to ferry everything – materials, plant, men, waste – in and out of that single passage,’ says O’Keefe. ‘It’s accessed via St Giles road, which is one

of Oxford’s main thoroughfares, so tightly scheduling deliveries was vital to avoid any disturbance,’ he adds.

‘The site was so inaccessible we had to erect the tower crane inside the building and work around it,’ says HBG construction manager Anthony Nagle. ‘At around 40m tall the crane has a jib capable of lifting a maximum 6.5 tonnes at 60m full outreach – that’s enough to lift anything coming onto site. When the job’s finished a huge mobile crane will lift it out through the roof and over the Cockerell building. We’re expecting a crowd for that one.’

I’ve heard people compare entering the building to Dr Who’s tardis

Anthony Nagle, HBG Construction

With the passage the only way out of the site, it was a case of building themselves out of the job as HBG completed each level of the concrete frame in stages from south to north towards the rear of the building and then out through the passage. ‘It got to the point where there was just a tiny area you could back a lorry down,’ says O’Keefe.

The building, largely hidden externally, has a surprise internally: a huge atrium space at it’s centre. ‘I’ve heard people compare entering the building to Dr Who’s Tardis. It is quite startling to experience this much light and space unexpectedly,’ says Nagle. ‘The towering atrium penetrates the entire five storeys and is flooded by light from a 15m x 5m roof light above.’

The atrium is one of several physical and visual devices used by Rick Mather architect Stuart Cabe to enhance visitors’ experience.

A staircase to the roof, zigzags up one side of the atrium, stepping back at each level as it rises, further enhancing the feeling of space. Constructed with reinforced insitu concrete it will be clad on one side with Portland stone and on the other with polished plaster. A glass/stone balustrade will add a transparency effect.

The new galleries could have felt cramped, as they must match up to the floor heights in the original Cockerell building. To overcome this potential problem, the architect and the museum’s conservators devised a new display concept for the galleries which in turn has informed the building’s architecture.

The new concept, Crossing Cultures, Crossing Time (CCCT), aims to show how the civilisations that shaped modern societies developed as part of an interrelated world culture rather than in isolation. Architecturally this translates to the interlocking of single and double-height galleries. ‘By visually and physically linking the single and double-height galleries, visitors will feel more comfortable inside the building,’ says Hobby.

Slim steel bridges which traverse some of the atrium and double-height spaces linking different galleries together are already in place. ‘These are extremely slender and incorporate glass balustrades to increase the feeling of openness, whilst reflecting the CCCT concept,’ says Nagle. Each bridge is wide and very heavy – the heaviest weighs in at about 9.2 tonnes – and built using 15mm-thick solid steel plates top and bottom with a welded fin incorporating services sandwiched between. Steel brackets anchor each bridge to the concrete frame.

The need to maximise space has also led to the invention of a new concept: the ‘fat wall’. ‘Rerouting services through “fat” widened walls instead of through suspended ceilings meant we could increase the ceiling heights,’ explains Nagle. ‘The fat walls also incorporate spaces for exhibition display cases – another technique devised to maximise gallery interiors. These protrude just 75mm from the surface of the wall.

It meant a lot of work for us co-ordinating with the museum and the fit out team. State-of-the-art ventilation systems were also fitted to preserve the artefacts.’

An air circulation system also runs through the walls, drawing in heat generated as people walk around the museum through openings at the top of the fat wall and pumping it back out through a plenum at the base.

Construction work on the Ashmolean is continuing apace. The concrete frame is up, as well as the structural steelwork for the atrium’s rooflight and to house a rooftop cafe. Structural carpentry has begun, alongside internal works in the galleries, lower ground and ground floors.

Work is due to finish next January, and the completed building should be open in autumn 2009. It should be worth a visit, as long as you remember that looks can be deceptive and it’s what’s inside that counts.