Temperate House at Kew Gardens reopens

Donald Insall Associates as Architects

The design and construction of the Temperate House (1859-1899) at the Royal Botanical Gardens, Kew was predicated on a Victorian obsession with the observation and study of the natural world. On reopening in May 2018 after a major five year restoration programme with Donald Insall Associates as the conservation architects, the Victorian glasshouse will continue to fascinate researchers and visitors alike. Its collection of 10 000 plants from around the world, including many rare and threatened species, will also be better cared for in a building where the environment can be fine-tuned using modern technology.


Designed by Decimus Burton (1800- 1881), the Temperate House is a series of five Grade I Listed pavilions standing prominently on a raised earth mound, aligned on an axis with the Kew Pagoda. It is one of a number of other Decimus Burton projects at Kew that include the Victoria Gate and the majestic Palm House. Covering a floor area of 4,880 square metres and extending to 19 metres in height, the Temperate House is twice the size of the monumental Palm House. It is, in fact, the world’s largest Victorian glasshouse and is often described as an “architectural wonder”.


Donald Insall Associates were appointed in 2012 as conservation architects to the Temperate House as part of a multidisciplinary team whose role has been to repair, restore and bring the building back to life for the general public. Importantly, the team’s brief was focused on creating an environment offering the best possible conditions for plants within the Temperate House. Improving standards of air-flow, for example, along with optimum lighting levels for plant life was foremost in the team’s mind.


This notion of “designing for plants” was something Donald Insall Associates was already familiar with at Kew having previously completed a Conservation Management Plan for the Temperate House. The plan has been instrumental in both the technical and visual approach to the restoration works. It also revealed how far ahead of his time Decimus Burton was when designing the Temperate House.


He was, for example, one the first architects in England to adopt the use of cement render which significantly sped up the building process at Kew. Burton’s ornate and distinctive ways of disguising building services are also now better understood through research conducted by Donald Insall Associates. To celebrate such revelations, the architects have repaired the ornate cornucopia urns that acted as chimney flues for the building’s now redundant boilers. Other original building services features have also been restored and retained as part of the building’s history. These include the entombed heating pipes and actuators, although neither of these is any longer in use.


Aimée Felton, Associate at Donald Insall Associates and Lead Architect on the project, says:

“Every conservation technique has been realised in a way that retains the bold spirit of this elegant marriage of Victorian architecture and engineering. To this end, we have employed the many different tools and approaches of conservation architecture to breathe new life into the Temperate House. These include restoration, reconstruction, preservation and adaption. ”In our approach to the project we have benefitted from Donald Insall Associates’ 60 years of expertise working on significant historic buildings. We have also carried out our own painstaking research on Decimus Burton and the Temperate House taking samples of old materials and studying these carefully whilst working with the highly skilled craftsmen to ensure all interventions have integrity and to ensure that this unique building will flourish for future generations.”


The Process

As part of the enabling works, the building was stripped of its living botanical collection, save for nine trees which were deemed too horticulturally significant to risk moving. The very memory of the plants, even when absent, is apparent in every joint opened by root systems, in remnant plant hooks and in exhausted soil.

Paint analysis revealed that early decorative schemes within the 1860s buildings had stone- coloured walls with pale blue and off-white decoration on the structure. The later-19th-century North and South Blocks originally had a dark green colour scheme. The modern titanium dioxide white decorative scheme first applied in the 1950s has been replaced with polychromatic stone colours, picking out architectural details and high level sculpture, following the paint analysis research.


Cleaning of the structure, utilising ultra-high pressure water and crushed garnet blasting to remove the build-up of corrosion, has revealed the original casting marks and metalworkers’ stamps, evidencing the quality and pride in craftsmanship of the Victorian era. New stamps will be added where new materials are used including lead work, replacement castings to the snow guards and finial details. Stamps have been omitted purposefully from the new glazing to maintain the purity of light transmission and reflection. These works acknowledge the passage of time and Donald Insall Associates’ part in that process.


Technical

To facilitate the re-painting and re-glazing of such a large structure 69,151 individual component parts had to be dismantled, recorded, logged and stored. Using tablets with latest coding software has allowed the team to do this and register originating position, grid line and current location. In retrospect, dismantling the building was the easy part. Reinstatement created many challenges especially when working in contemporary elements into the structure whilst taking into account the aged junctions and weathering details.


Apprenticeships managed by Royal Botanical Gardens Kew

Sixteen apprentices have been employed as part of the project, learning the skills of building conservation and horticulture. The project has developed strong local connections between education and place. It has also reinforced the critical scientific work undertaken at Kew and the sublime architecture within its grounds.


Better visitor experience

Landscaping, both internally and in the approach to the building, has been improved, providing inclusive access to all visitors. The visitor experience will also be enhanced through interpretation facilities, guiding the passage of the public through a suite of five interconnected buildings. This will allow visitors to take in temperate worlds, all the while located in leafy suburban TW9. A new dedicated education space on the site will offer Kew greater opportunities to engage with their audiences and reinforce the scientific basis of its foundation.

The Temperate House opens on 5 May 2018, marking the end of the practice’s six-year tenure on this project. However, Donald Insall Associates’ involvement at Kew Gardens will continue, with exciting prospects ahead including several private residences within the estate.


Aimée Felton, Associate at Donald Insall Associates and Lead Architect on the project, says:

“The restoration of the Temperate House has been a complex and immensely rewarding project, recalibrating contemporary understanding of Victorian architecture and the development of past innovations. New glazing, mechanical ventilation systems, path and bedding arrangements all took their founding principles from Decimus Burton’s own drawings, held within Kew’s archives.

The time it will take for the newly propagated plants to reach maturity will offer visitors a full and unobstructed view of the incredible metal skeleton in all its glory: a cutting-edge sanctuary for plants.”


Temperate House Timeline

1845-1861 Design of Temperate House Decimus Burton

1860 Temperate House constructed

1863 Original opening of the Temperate House

1970 Temperate House fell into disrepair necessitating its closure

1979-1982 Last restoration work by Property Services Agency

2003 Royal Botanic Gardens declared a UNESCO World Heritage Site

2012 English Heritage proposed placing Temperate House on the Buildings at Risk

Register

2012 Conservation Management Plan by Donald Insall Associates

2013 Temperate House closed for works to reopen in May this year

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