Exposed, geometric concrete is making a comeback in Sheffield with an award-winning complex of artists' studios designed by Feilden Clegg Bradley. But, wonders Martin Spring, will it stand the test of time?
Is New Brutalism ripe for a comeback? The 1960s' taste for raw concrete was hailed by architects as heroic, honest and uncompromising – but was given a decisive thumbs-down by the public, who saw how the British weather took its toll on the absorbent grey material. Now, four decades later, exposed concrete once again exerts an irresistible pull on the younger generation of architects.

A case in point is the £4.25m complex of 51 artists' studios in Sheffield city centre. The architect is Feilden Clegg Bradley of Bath, which is more usually associated with richly textured buildings in brick and timber – but not so here. Known as Persistence Works, the 4000 m2 building takes the form of two parallel slab blocks in smooth fairface concrete – pale grey, unadorned, and austere. At the entrance end, however, this buttoned-down composition suddenly flowers into a sculptural flourish of thrusting cantilevers, sharp angles and curved forms.

Neo-new-brutalism, you could call it – if you wanted to be really brutal, that is. But is the use of concrete here appropriate or merely indulgent? Has it been specified and detailed to counteract the obvious weathering defects of 1960s buildings? And will the public's reaction be any different this time round? Fellow architects, it has to be said, have been beguiled by Persistence Works, and last week hung a national RIBA award on it.

Aside from its bold architectural styling, Persistence Works makes another significant contribution to building design. Yorkshire ArtSpace Society, the developer and owner of Persistence Works, says it is the UK's first purpose-built complex of studios with a shared reception. By tradition, artists' studios are run-down former industrial buildings offering large spaces at rock-bottom rents. Indeed, ArtSpace previously occupied just such a building – a former cutlery factory – a stone's throw from the new building. So well did ArtSpace and its community of artists thrive in this environment that it set the scene for the surrounding district, which was designated the cultural industry quarter by the council.

By 1995, however, ArtSpace had outgrown the cutlery factory, which had never solved the problem of manhandling large, modern artworks – including a 20 ft high steel camel – in and out of the cramped six-storey building.

Kate Dore, Artspace's irrepressible director, relates what happened next: "We drew up a brief for the sort of spaces we wanted. Estate agents said such a building didn't exist. So we thought, why don't we build one ourselves?" Energetic lobbying and organising brought in a £3.7m grant from the Arts Lottery Fund, another £1.5m grant from the European Regional Development Fund and a site from the city council.

A short-list of designer architects was drawn up including Penoyre & Prasad, Stanton Williams, and John McAslan + Partners. Selection through competitive interview came down to personalities, admits Dore. "Feilden Clegg Bradley came across as down-to-earth and very eager to collaborate with artists by using their work as integral to the building rather than just being glued to the outside. They were also the only practice represented at the interview by a woman, Julia Kashdan-Brown."

Feilden Clegg Bradley's design solution was to run two longitudinal blocks parallel to each other. A two-storey block, which is placed hard up to the pavement of Brown Street, contains the larger studios with the main entrance and reception hall at one end. Behind it rises a six-storey block containing smaller studios opening off central corridors.

The two blocks are separated by a double-storey-height mall, through which larger artworks can be lifted in and out of the studios overlooking it. The mall conveniently doubles as an informal exhibition space.

The arrangement offers a variety of studio sizes and levels of daylight to serve a range of artists, from hefty metal bashers to fastidious jewellers, weavers and illustrators. The larger studios on the upper floor of the lower block, for instance, are each graced with two combined rooflights and clerestory windows that stretch across the front and rear of the high ceiling, but only one tiny window on the external wall. Brian Jackson, one of the occupants who works surrounded by his huge abstract oil paintings, comments with satisfaction: "I need wall space." Even the radiators are ceiling-mounted and fan-assisted to leave more hanging space.

But why the ubiquitous insitu concrete, which is used not just for the structural frame but for the self-finished building fabric? And even where the concrete runs out, as in the internal partition walls, it gives way to exposed grey, concrete blocks. Why not use more reassuring brick, as in the old cutlery factory? "It was quite a scary prospect to use concrete," admits Kashdan-Brown. "But we thought that a studio complex was a new building type that called for a new form of expression. We felt that we could explore and manipulate concrete like an artist with raw materials. The aspiration was to use a robust and ordinary material in a unique way, which seemed fitting for a building where fine arts and crafts were to be used. We also thought it should retain the quality of old warehouses from Sheffield's industrial quarter."

The character of the finished building is industrial to a fault. Viewed from the front, the walls are flat, smooth skins with strip windows set flush with the external surface. Out of the rear wall of the six-storey block, double-storey-height balconies are gouged. Internal and external walls, ceilings and floors are hard, utilitarian and grey, with surface-mounted electric trunking and ductwork and industrial pendant lights. If anything, the building brings to mind local authority multistorey flatted factories.

Kashdan-Brown admits that the building had originally been designed with more texturing and modulation in the form of blue colouring, ribbed surfaces, external cornices and deep-set windows, but these had all been stripped away to fit the budget after tendering. Even so, considerable effort was put into refining the concrete specification and detailing, involving structural engineer Buro Happold and main contractor Gleeson (see "Exposed concrete without tears", previous page).

To those willing to suspend common prejudices against concrete, the building does exhibit special qualities. Unlike the exposed concrete of the 1960s, the material here is of a consistent, creamy, light-grey finish – even in the rain – with a strokeably smooth surface. Cast panels are edged by precise V-joints, and they combine with the flush windows to tap out a subtle rhythm across the flat, crisp-edged skins of the external walls. And at the entrance end of the building, the disciplined linear blocks have been allowed to break into a joyous little dance involving an outward-jutting upper floor, a sharp, prow-like corner and a twisted crescent – all in exposed structural concrete.

Yet another reason for adopting concrete as the main material is that, in Kashdan-Brown's words, "the building provides a backdrop to the artwork". Seven creations by resident artists have been incorporated into the fabric, the most prominent being a patterned glass screen by Jeff Bell, which borders the pavement along the front facade. The screen of translucent glass panels combines an intriguing textured surface created by the imprints of cutlery with a shimmering effect caused by a backing of shiny aluminium foil.

The 89 artists seem to have taken to the building like ducks to water, with the industrial finishes relatively resistant to their attendant mess. As for director Kate Dore, she can hardly contain her delight. "The building is phenomenally successful – we now have 60 on our waiting list," she enthuses. "When you walk inside, it has a really warm, open, light, bright, sturdy feeling. The spaces work well together. And I adore the concrete – I love stroking it."

To casual visitors, the building does exhibit an austere, disciplined integrity. The structural concrete acrobatics around the main entrance rise attain a heroic level, but as they are executed in pale grey concrete, they all too often recede into the dull, grey skies of Yorkshire. In the final analysis, the building, like its 1960s predecessors, will stand or fall on how well it weathers over the years. This is where the painstaking design skills of Feilden Clegg Bradley will come into play.

Exposed concrete without tears

At Persistence Works, reinforced concrete has been cast in situ to construct self-finished loadbearing walls and floor slabs. Its specification and detailed design were carefully researched and repeatedly tested to avoid the poor finishes and weathering that blighted exposed concrete buildings in the 1960s. The costs of all concrete works (excluding substructure) equate to £275/m2 of gross floor area. The concrete was supplied by RMC Readymix and cast by the main contractor, MJ Gleeson, with the steel shutter pans supplied by SGB Scaffolding. Concrete mix
Smooth, light-coloured concrete was desired by the architect, but white cement was ruled out as too expensive. Instead, a GGBFS fuel ash was used as creamy-grey coloured cement substitute in 60:40 mix with ordinary Portland cement. A fine, consistent mix was achieved by using rounded gravel of maximum 10 mm size. Cracking caused by shrinkage and tensile stresses was eliminated by using the fuel-ash mortar and additional reinforcements respectively. Fairface finish
A smooth fairface finish was achieved using phenolic-faced plywood to line the steel shutter pans. Detailing
The flush surfaces of the concrete walls are divided into panels by distinct V-joints. The joints were cast using simple plastic extrusions that are commonly used for kitchen and bathroom tiling and could be readily stripped out without damaging the surface. The same joint was used for three conditions – the constructional joint between concrete pours, movement joints and false decorative joints used to create a regular pattern of panels. Copings, cornices and other devices were eliminated to cut costs. Thermal insulation
In the external walls, insulation is provided in the cavity between the outer leaf of insitu concrete and the inner leaf of concrete blockwork. Workmanship
The highest class C of concrete quality was specified. However, several arrises to the V-joints were defectively cast, and these were made good using a meticulous repair technique that did not need to be rubbed down, and which matched the surrounding concrete perfectly. Sealant
To counteract weathering and staining, a water-repellent sealant was painted on all exposed concrete surfaces. The coating, Keim Mineral Products’ Lowtexsan, is clear, colourless and virtually invisible on the surface of the concrete. A further advantage is that, as the coating is water-repellent, the underlying concrete does not turn a dismal dark grey in the rain.