The iconic and instantly recognisable external facade of Park Hill Estate, SheffieldThe Park Hill Estate in Sheffield was built as a council estate between 1957 and 1961. It was designed by Jack Lynn and Ivor Smith in a brutalist architectural style and has always divided opinons. Described as revolutionary for its time, the concept was `Streets in the Sky` with wide deck areas and distinctive concrete frame. Whilst demolition of the site was being considered, in 1998 the estate was listed by English Heritage and given Grade II* status which was considered very controversial and attracted much criticism. It is the largest listed building in Europe and, with its protected status, it was decided to renovate and redevelop the site as a joint venture between Urban Splash and English Heritage.

The future of the scheme was to develop the site into desirable upmarket apartments, business units and social housing and the success has been widely publicised, including features in almost all architectural and concrete magazines, with a shortlisting for the 2013 RIBA Stirling Prize.

The key involvement for Keim Mineral Paints was renovation of the extensive concrete frame. The discoloured concrete gave a drab and dirty look to the building – not the desirable, upmarket effect that the designers were looking for. The first consideration was to paint the frame in its entirety but this would have led to the loss of what is considered to be the most iconic feature of the building. So the challenge was to renovate the frame, improve the colour and finish without creating a painted effect.

The answer was to use Keim Concretal Lasur. This innovative paint system is a colourwash or stain which is applied onto concrete to cover blemishes and enhance the appearance, whilst, most importantly, keeping the look of natural concrete. Keim Concretal Lasur has all of the features integral to Keim Mineral Paints such as a permanent and highly protective chemical bond, complete UV stability and resistance to mould and fungal growth. Keim Concretal Lasur is diluted with a complementary product using differing ratios and opacities to achieve the required colour and coverage, whilst still enabling surfaces to look like unpainted concrete. The system can also be employed to minimise any unsightly repairs to concrete. The versatility of the system allows almost complete coverage of repairs, or slight coverage, if preferred, which enhances the natural look of the concrete but gives the effect of a more visually appealing finish.