Cast your eye

Stockport-based concrete specialist SCC is a private limited company set up in Manchester more than 21 years ago. After spotting a niche market in construction and grabbing it, the company became a design and build main contractor.

Having specialised in in-situ reinforced concrete until the late 1980s, the company identified a healthy market for prefabricated components and went on to form an association with consulting engineering practices.

It was not long before the company recognised opportunities in structures that most people saw as the ultimate in monolithic concrete eyesores: the much-maligned multi-storey car parks (MSCPs).

"Multi-storey car parks have a bad name because of those built in the 1960s," says Glynn Rhodes, a partner with Harrogate-based consulting engineer Hill Cannon, which has worked for SCC. "They were concrete boxes that were put up with little thought and many now need demolishing."

Not only were MSCPs ugly, they were perceived as being unsafe as well. According to Peter Crofts, SCC precast design build manager, one of the reasons for this was (unlike public buildings and bridges) there was no requirement, until recently, for structural checks on MSCPs.

However, changes are under way. In line with recent guidelines issued by the Institute of Civil Engineers, more care is being taken in their design. An example of this is a structure SCC completed last year: a six-storey MSCP outside Sheffield railway station.

Intended for the sole use of rail commuters, as opposed to shoppers, the MSCP offers 684 spaces on six levels and is clad in pre-cast concrete architectural panels. A local artist supplied designs for the in-fill panels on the structure's gable ends.

"Although you need a lot of openness with a car park, in that there have to be plenty of fresh air openings, the last thing planners want is to see is the raw structure," explains Crofts. "It might still be accepted at airports, but not in a city centre."

Ingenuity is called for in the design of an MSCP, particularly in the case of the car park destined for Sheffield's rail commuters. For while the layout of the core structure cannot change, the shell is expected to blend in with the surrounding buildings.

But before architects get excited about MSCPs and their potential for sweeping flights of fancy, Crofts adds a rider. "With a car park, the emphasis is on the engineering. If you start messing around with fancy floor plates, you run the risk of ending up with a car park with lots of columns that people can't drive around. The interior is the primary consideration and the shell is the add-on."

An ingenious design has been used at Sheffield. It is called the Vertical Circulation Module (VCM) layout system, and Hill Cannon believes it is unique in that it eliminates the need for special pedestrian ramps - thus creating more car parking spaces - and gives pedestrians flat access to all parts of the parking decks, which is particularly helpful for people with pushchairs, shopping or luggage trolleys.

Initially, VCM is a flat plate that comprises eight 2.4m-wide stalls that enable an 18.8m diameter turning circle. "A good car park is one that people of all driving abilities can drive around," says Hill Cannon's Rhodes.

The access way linking adjacent decks is level on its outer edge and slopes at one in 20 on its three inner sides while all other surfaces remain plane (see diagram, left). In the middle of the access way, the slope is one in 40. However, Rhodes says that this is of little consequence to motorists and pedestrians alike.

"The perfect layout is a totally flat deck that allows pedestrians to negotiate walkways with good surveillance," he adds.

Despite the sophisticated level of engineering, there is still plenty of scope for architects to display their abilities.

Proof of artistic ingenuity is demonstrated at another SCC project. At Leith's Ocean Terminal in Scotland, both ends of the MSCP were designed to look like the bow and stern of an ocean liner with wooden shutters emulating towels hanging over the ship's rails.

Other ways of softening the customary severity of an MSCP's appearance, and thereby escaping the clich' of the concrete box, include incorporating planters with automatic sprinklers to achieve that verdant appearance. The aim is to achieve a tiered look or, as is the case at Sheffield, to surround the structure with pre-cast concrete panels that incorporate specially chosen sand (intended to resemble Bath stone) along with terracotta coloured bricks.

MSCPs used to be constructed out of 100% in situ concrete. The ratio has moved to 80% of precast concrete components and 20% in-situ. But SCC has gone even further.

By producing the majority of the components in its manufacturing unit at Reddish near Stockport, Crofts says that 98% of the Sheffield MSCP is prefabricated, with the remaining 2% of the concrete structure poured in-situ.

"Once a deck's components have been laid, we stitch them together with in-situ concrete," explains SCC construction director Eamon O'Donnell.

O'Donnell acknowledges that SCC's success in taking a leading role in the market is thanks to the close relationship the company has built up with practices like Hill Cannon.

"We have both fed off each other's expertise and we've broken down the in-situ market and turned it into a pre-cast composite option," says O'Donnell.

The company refuses to rest on its laurels. Having had a hand in turning round the production method, O'Donnell sees long-term advantages for SCC as a design and build main contractor. "With obvious benefits in terms of increased quality for local authorities and clients," he says. n