10 C O N T E X T 1 4 4 : M A Y 2 0 1 6 Last renovated in 1970 by Posford, Pavry and Partners and nowby a teamwithDonald InsallAssociates as conservation architects,the precinct is in need of a comprehensive restoration, reinvigoration of visitor interpretation and improved access.The building houses important historic living plant collections, including a number of plants of exceptional size and unique heritage value. TheTemperate House range of buildings has a number of longstanding defects, all related to inherent failures in the original construction detailing. As an architect, Decimus Burton was a leader in the innovative use of metalwork for large spanning structures and in the early use of cement. Study of the extensive archive records, including original drawings held at the National Archives, has helped inform the subsequent restoration. The North and South Blocks both, unusually, incorporate wrought-iron posts and angled braces in their masonry piers, possibly to speed up construction, enabling the main structure to rise before the masonry was completed. This feature is coupled with the use of dense cementitious renders throughout the whole building. Together these give rise to problems of entrapped moisture, iron corrosion and cracking of masonry. Without complete dismantling and rebuilding of the structure, the solution proposed is the introduction of a new cathodic protection system, designed by Ramboll UK, the structural engineer on the project. It is hoped that the range of techniques proposed will suppress the corrosion of the metal structure and metal components within the masonry by providing the electrochemical condition to control the corrosion process. This will result in less cyclical differential movement and resultant cracking of the cement render. This restoration, project-managed by Turner + Townsend, will strip the building down to reveal its original metal and masonry core, carry out repairs, and repaint with the latest high-technology, long-lasting and protective paints.The existing irrigation and ventilation systems are no longer functional and sustainable; effective solutions are being implemented to provide the very best conditions for the new collection of plants. The existing piped and electrical services, largely more than 30 years old, are reaching the end of their lives.They no longer comply with contemporary codes of practice and the two Octagon Basements services areas were badly planned and arranged. Royal Botanic Gardens Kew was the first UNESCO world heritage site to receive the ISO14001 standard. As such the organisation believes that its operation should be undertaken with minimal adverse impact on both the local and global environments. Environmental considerations are therefore at the heart of RBG’s corporate strategy. In line with this ambition Hoare Lea, consulting services engineers, have designed a new heating and servicing strategy for the building, utilising a new biomass boiler situated within the, back-of-house, StableYard Energy Centre to provide sustainable energy for the heating of the glasshouse. The original glazed roofs of the Temperate House included hand-operated timber sash frames.According to site notes from the 1970s, these were beyond repair and were replaced with an aluminium glazing system.As part of the current restoration, the aluminium system is being overhauled and cleaned, fitted with improved glazing and connected to a new actuator opening mechanism to provide the fine control of ventilation required by the horticultural team. Scaffolding rising in Centre Block (Photo: Donald Insall Associates)
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