Stunning Savill Building opens to Royal approval
Buro Happold-engineered timber structure is graceful new landmark for Windsor Great Park
The UK’s largest timber gridshell structure, the roof of The Crown Estate’s new Savill Building at Windsor Great Park in Berkshire, has been officially opened this week (26 June) by HRH the Duke of Edinburgh. Buro Happold provided the structural engineering design for the roof of the building – a spectacular yet graceful, 90m long by 25m wide three-domed undulating timber structure – which will form a new focal point for the park. It has been open to the public since 27 June.
As well as the flowing shape of the exterior, intended to mirror the skyline created by the trees surrounding the structure, the gently curving grid of the timber gridshell – clearly visible on the inside – provides another impressive view of the building. Having the structure on display gives a remarkable insight into the way the roof works and proves that a building’s structure and interior can be as graceful as its exterior.
The building, located in the Savill Gardens in the south-eastern corner of Windsor Great Park, houses a ticket office, shop, self-service restaurant, seminar rooms, offices and a small garden centre.
The brief from the client, The Crown Estate, created some seemingly contradictory demands which are met by the choice of the timber gridshell. The roof uses the latest technology and engineering expertise alongside traditional craft skills to create a structure which is dramatic yet sensitive to its surroundings. Buro Happold engineers worked closely with the team at Glenn Howells Architects, to successfully create a structure made of timber sustainably harvested from the woodlands of Windsor Great Park.
More than 20km of 80mm by 50mm larch timber is used in the gridshell. The gridshell roof structure weighs 30 tonnes – much less than a similar roof in concrete, reducing the loads on the legs and foundations.
This is the latest timber gridshell that Buro Happold has designed, continuing a lineage of lightweight, environmentally sensitive structures that goes right back to the practice’s roots 30 years ago (See note 1, below). The design of this gridshell builds on the experience gained in the engineering of 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. The Savill Building project reunited Buro Happold with the Green Oak Carpentry Company (GOCC), the woodwork specialist which also worked on the Downland gridshell.
Richard Harris, Buro Happold associate director and lead engineer for the project said: “This has been a great project to work on and the end result is as impressive as we all hoped it would be when we saw the initial design.”
“It’s been a real team effort and while Buro Happold brings great structural engineering knowledge and experience, this amazing gridshell would not have been possible without the design flair of Glenn Howells Architects and the remarkable three dimensional understanding of wood that the Green Oak Carpentry Company has,” said Harris, who also worked on the Downland gridshell.
“Close collaboration was also required between us and HRW engineers, who looked after structural engineering for the rest of the building,” added Harris.
A gridshell is based on the naturally strong structure of a shell. It can be constructed of timber, steel or concrete – it is effectively a shell with holes, with the structure concentrated into strips.
Timber gridshells are immensely strong, but while under construction the individual timber elements are pliable. This allows for the structure to be deformed into a shape and then locked in the desired form. The components of the shell are laid out on a flat platform and then carefully raised or lowered into the desired shape. For the Savill building roof this was achieved through a bespoke scaffolding system through which the height of the roof was adjusted at 200 points across the plan area.
A double curved structure can minimise use of materials in spanning a space through using a set of straight, prefabricated, identical components. The Savill gridshell is made up of a regular one metre grid of 80mm x 50mm sections of larch timber.
Ideally, a gridshell would be supported firmly all around its perimeter, as is the case with the Downland gridshell where its walls are part of the timber gridshell. But to accommodate the dramatic structure envisaged by the architect, which includes high openings into the surrounding gardens, the Savill Building roof is supported at discrete points on steel quadruped legs. To contain the load concentrations of the structure, steel tubes were also introduced for the perimeter ring to which the wooden structure is bolted on to.
To act as a shell, the structure must be strong and stiff in its plane. Initially the concept included steel cables to triangulate and thus brace the shell in its plane. But to save cost and make a more elegant structure the cables were omitted and the plywood covering, which is needed to support the raised seam roof, was used instead. In supporting roof loads, this in-plane structure is just as important as the more visibly obvious laths.
On top of the gridshell is 160mm of insulation, covered by an aluminium roof system and a profiled standing-seam skin which is the waterproof layer and support for the oak rain-screen. Oak was specified for its natural resistance to the elements and for the silvery-grey look it will assume as it weathers.
Project team
Client: The Crown Estate
Architect: Glenn Howells Architects
Buro Happold services: Structural engineering (for the roof only)
Woodwork contractor The Green Oak Carpentry Company
Structural engineer for the rest of the building HRW Engineers
ENDS
Background information for editors:
Press office and practice information at www.burohappold.com
Contact:
Neil Wilks
Press officer
Tel: 01225 321764
Email: neil.wilks@burohappold.com
Images of the Savill Building are available. Please contact the press office.
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, disability design consultancy, project management, urban design and a range of specialist CAD services.
Note 1 Buro Happold founder Ted Happold was involved in making the world’s biggest timber gridshell before the practice was formed. He had, while at Ove Arup and Partners, worked with architect Frei Otto on the Mannheim gridshell in Germany in 1975. Given the many benefits of the construction method, which enables double curved structures to be constructed quickly, efficiently and cost-effectively, Ted was a firm advocate of timber gridshells and would often remark that he could not understand why it was not more widely adopted.
The Savill Garden, a royal garden, set in a royal landscape, is one of the greatest woodland gardens in England. The work of master landscape gardener Sir Eric Savill, it was created in the 1930s, and offers visitors interest year-round with its colourful displays of interesting and rare plants.
The opening of The Savill Building in June 2006 provides, for the first time, a visitor centre worthy of Windsor Great Park. Built to a unique and innovative gridshell design, made with timber harvested from Windsor Great Park, The Savill Building forms the gateway to The Savill Garden and The Royal Landscape. In addition to exhibition facilities, visitors to The Savill Building can enjoy a delicious selection of food and drink in the restaurant run by the esteemed caterers, Leith’s, and choose from a range of plants, gifts and books in the new shop.
The Royal Landscape is an area of a thousand acres of gardens and parkland, accessible to the public, at the southern end of Windsor Great Park. It includes The Savill Garden, The Valley Gardens and Virginia Water lake. It is a man-made landscape, which has been shaped and planted over a period of 400 years. Visitors can find further information by logging on to: www.theroyallandscape.co.uk
The Crown Estate is the owner and steward of Windsor Great Park.
The Crown Estate is an estate valued at more than £5 billion, including substantial blocks of urban property, over 120,000 hectares (300,000 acres) of agricultural land in England, Scotland and Wales, and around half the foreshore, together with the seabed out to the 12 mile territorial limit.
As owners, managers and guardians of one of the world’s most important and diverse urban, rural and marine property portfolios are underpinned by the three core values of commercialism, integrity and stewardship.
The Crown Estate is part of the hereditary possessions of the Sovereign “in right of the Crown”, managed under the provisions of the Crown Estate Act 1961 by The Crown Estate who have a duty to maintain and enhance the capital value of the Estate and the income obtained from it, which goes to the Treasury for the benefit of the tax payer.
www.thecrownestate.co.uk
