Polished performance

Its exterior is a riot of colliding textures and colours – brick, terracotta tiles, glass and stone all vie for attention – but the floor surfaces inside Plymouth’s Drake Circus shopping mall are made from a single material: polished pink granite.

This project serves as a showcase for Chinese granite, an increasingly popular specification choice, and the Xiamen factory in particular. But it also highlights a potential problem with natural stone flooring – it’s slippery when wet.

Completed in November last year, Drake Circus is a covered shopping centre built by Bovis Lend Lease for P&O Developments.

It was conceived to replace a 1970s complex which, with its poorly designed public spaces and use of low-quality materials – it suffered from ‘concrete cancer’ – was well past its sell-by date.

The hope is that the new Drake Circus, designed by retail expert Chapman Taylor, will provide shoppers with a centre that will last well into the future. Its longevity will be due, in part, to the high-quality materials specified throughout the development, and the flooring was a critical element.

Stone specialist Szerelmey was responsible for the £1.2m flooring works, which covered 5,400m2 over three storeys. The cost of the granite was £35/m2 and was part of a £2.2m contract which also included stone cladding.

Szerelmey’s senior contracts manager Gary Williams had already sourced products from China on a previous job. Nevertheless, he describes working with the emerging Chinese market as a learning curve. ‘I won’t say it’s easy because it’s not!’

‘There’s a basic lack of stone knowledge in China and a huge variance in the quality of production facilities,’ adds Williams. At Drake Circus Szerelmey was able to pass huge savings on to the client because of reduced material costs, but in its first experience of sourcing from China profits were hit by poor cutting tolerances. ‘We spent as much money rectifying the problem because the range was so different. We had to reorder a lot of material,’ says Williams.

It was a different story when Williams began sourcing for Drake Circus. With the architect, contractor and client, he travelled to China to meet up with stone company Best Cheer, which operates the biggest cut-to-size stone facility in the world at its Xiamen factory. After selecting the granite, Best Cheer dry-laid the entire mall floor to see how all the pieces fitted together. Consequently it was easy to spot any delivery errors, which on Drake Circus, were negligible. ‘If a stone was scheduled incorrectly it wouldn’t fit so we’d know instantly if there was a problem. Bearing in mind you have five weeks on a ship and customs to clear, it’s a weight off your mind,’ says Williams.

Szerelmey was on site at Drake Circus for 14 months, starting in August 2005. The Chinese granite tiles sit on two different beddings, one reinforced, the other standard. The ground floor, which features a flamed surface finish incorporates manifold underfloor heating systems (see diagram, left) and Williams says the installation of this was relatively painless. ‘I think in total we laid around 2200m2 of heated floor and we had to remove about 6m2 because of one leak – on a site that size, that’s pretty good.’

Williams used a number of techniques to ensure the job was well managed and completed on time. For example, to cure the concrete and release water from the make-up his team attached boilers to each underfloor bail and ran hot water through them over Christmas. This meant the floor was ready for the tiles to be laid after the break.

Williams wanted to steer clear of night shifts, which are often considered necessary for flooring contractors as the end of the project looms. ‘When you’ve got guys working on the day shift, switching to the night and then back again causes metabolism problems that result in sluggishness and poor workforce efficiency,’ he says.

Furthermore, Williams went the extra mile when interpreting the architect’s specification. One small area of flooring at Drake Circus required reinforcement despite no instruction on the drawings. So Szerelemey strengthened the make-up with an anti-crack mesh, placing it just off the bottom of the sand cement bed. ‘It wasn’t asked for, it wasn’t paid for, but it was the right thing for us to do.’

The granite needed to be protected. Large maintenance equipment is used for cleaning the windows and during the build, this plant posed a risk of cracking the floor. ‘We ran two layers of plywood over a soft membrane, to prevent scratching. It can take the weight of heavy machinery too,’ says Williams.

Once the granite had been specified the inherent problem of what to do with wet, slippery floors needed to be addressed. Sandberg, which did slip testing on the granite (see box, left), recorded very good results for dry conditions – ranging between 74 and 85 (extremely low potential for slip) depending on surface roughness, but delivered a 6 (high potential for slip) under wet conditions.

Downstairs the designer specified a flamed granite around the entrances. ‘Flamed’ means a thermal shock, usually a hot gas flame, has been applied to the surface and it roughens the stone up, making it less slippery. And it included self draining mat wells at the entrances to cope with rainy days.

Upstairs, the floor has not been flamed, and where smaller entrances open onto the polished surfaces, new mats have had to be put down. ‘We’d have taken a different approach had we been contracted for the design,” says Williams.

Drake Circus was a success for Szerelmey. Two months from completion it had finished 90% of the floor. Williams says: ‘It took a fair degree of fighting, kicking and scrapping... good management in other words. I did what a good contracts manager does – put people in line.’ If Williams sounds like a bruiser, you’d be wrong. He says that because most of the team were working away from home and separated from their families, they socialised together. ‘It forged a strong team spirit and you begin to realise everyone’s human. So if you hit a major problem, you’re more likely to talk about it rather than pen a letter.’

It was this management nous, coupled with Szerelmey’s market knowledge and installation know-how that led to a slippage-free project.