Challenging restoration of historic orangery is achieved through teamwork
Buro Happold has played an integral role in the challenging design of a glazed timber gridshell roof to restore a Grade I-listed Orangery at Chiddingstone Castle in Kent.
The practice worked closely with architect Peter Hulbert in providing structural design advice for the 12m long by 5m wide Orangery roof, which has created a 21st century events venue at the estate near Edenbridge.
Located within Chiddingstone Castle’s picturesque grounds, the Orangery is an 18th century stone structure. The trustees of the estate were keen to restore its shell and provide a new roof to make the most of the Orangery’s licence for civil marriage ceremonies, as well as use it for other functions.
A timber gridshell was proposed as the solution for a lightweight modern structure that could be distinguished from the original Orangery structure. Buro Happold teamed up with woodwork specialists Carpenter Oak & Woodland to produce the single-domed, double-curved timber gridshell, using local chestnut as the main component.
The gridshell shape is generated by the length of each chestnut lathe, its starting position and orientation. The chestnut lathes that form the gridshell are 40mm by 30mm in cross-section, with 30mm by 34mm shear blocks between the two layers. They are secured to a ring beam and transfer the load through 10 galvanised steel columns to a new concrete raft foundation. This supports the new roof as a shelter independent of the historic structure within which it sits.
The laminated and toughened glazing is supported onto the timber structure by bespoke stainless steel fixings, which offer a degree of movement and up to about 50mm tolerance at each node. The fixings were designed by Antony Smith, former director of Haran Glass and now a director of newly-formed Inspiring Projects Involving Glass (IPIG). They integrate with a patented node clamp (designed by Buro Happold, The Green Oak Carpentry Company and Edward Cullinan Architects for the Weald and Downland Museum gridshell), which locks the double layer of criss-crossing chestnut lathes into a precise alignment and holds tension cables in place.
Buro Happold carried out extensive computer modelling to determine the curvature of the gridshell. It had to be subtle enough to enable it to be erected within the existing Orangery structure, yet dramatic enough to work as a design feature.
Richard Harris, associate director and leader of the timber engineering team at Buro Happold, said: “Chiddingstone Castle Orangery is one of Buro Happold’s smaller projects but has been incredibly challenging nonetheless. Although glass is a predominant feature of orangeries, its interface with a timber gridshell is an interesting development. No previous timber gridshell has supported frameless glazing before so, in that sense, it’s an engineering first.
“This sensitive restoration and refurbishment project proves the flexibility of gridshells, as well as the adaptability of the practice’s engineers and other members of the project team. The project has not been without its difficulties but the finished product is an example of high quality, fine craftsmanship.”
The residual space around the glass ellipsoid is filled with a copper clad lightweight timber deck, acting as a gutter.
Ends
Project team:
Client: Chiddingstone Castle Trust
Architect: Peter Hulbert
Structural engineering consultant: Buro Happold
Woodwork contractor: Carpenter Oak & Woodland
Glazing contractor: Antony Smith, IPIG (formerly of Haran Glass)
Groundworks / structural restoration: AM Design & Construction
Notes to Editors:
Buro Happold
Press Office and practice information at www.burohappold.com
Images of Chiddingstone Castle Orangery are available on request.
For more information, please contact:
Louise Gaiger
Press officer
Tel +44 (0)1225 321764
Fax +44 (0)8707 874148
Email louise.gaiger@burohappold.com
Buro Happold is a multi-disciplinary international practice of consulting engineers established in 1976 offering civil and structural engineering, mechanical and electrical engineering, quantity surveying, building services and environmental engineering, health and safety management, infrastructure and traffic engineering, ground engineering, façade engineering, fire engineering, computational fluid dynamics analysis, inclusive design consultancy, project management, urban design and a range of specialist CAD services.
Chiddingstone Castle Orangery’s gridshell roof continues Buro Happold’s lineage of lightweight, environmentally sensitive structures that goes right back to the practice’s roots 30 years ago. Buro Happold founder Ted Happold was involved in making the world’s biggest timber gridshell before the practice was even formed. He had, while at Ove Arup and Partners, worked with architect Frei Otto on the Mannheim gridshell in Germany in 1975.
Richard Harris was also lead engineer for the roof of the UK’s largest timber gridshell structure - The Savill Building at Windsor Great Park in Berkshire, which opened in summer 2006. In addition, he worked on the Downland gridshell at the Weald and Downland Museum in Sussex, completed in 2002. An artefact store and workshop for the museum, it was the first large timber structure to be built in the UK but is a quarter of the size of The Savill Building. Richard is also part-time Professor of Timber Engineering at the University of Bath.
Chiddingstone Castle
The historic building, which houses furnishings and paintings, Royal Stuart memorabilia, Japanese lacquer, Egyptian and Buddhist antiquities of passionate collector Denys Eyre Bower, is currently undergoing renovation. Eyre Bower left his home and its contents to the nation when he died in 1977. It is now owned by a registered private charitable trust, which is restoring the estate to its former glory.
For more information visit www.chiddingstone-castle.org.uk
