Westonbirt, the National Arboretum near Tetbury in Gloucestershire is one of the most spectacular collections of trees in the world. The 18,000 trees and shrubs, many planted in the mid-19th century, the heyday of Victorian plant hunters, are laid out in a Grade I-listed historic landscape of 600 acres (2.4km2) with 17 miles (27km) of marked paths for visitors.

Thousands of visitors a year come to see the rare and exotic trees planted in the Old Arboretum, the traditional working woodland dating back to the 13th century in the Silk Wood and, in autumn, the magnificent red blaze of its maples collection.

In 2010 the Forestry Commission, who own and manage the Arboretum, commissioned Glenn Howells Architects to develop a masterplan which, over the course of several phases, would improve the experience of visitors to the site. Improvement was needed; parking was haphazard; a single ticket hut caused long queues; toilets and café were scattered around the site and there was nowhere to provide information.

To address these pressing problems, Glenn Howells Architects has designed a new visitor centre, the Welcome Building, which stands at the main entrance to the Arboretum, its curved timber roof acting as a landmark to visitors arriving at the new car and coach park. (The former car park is now being restored to its original historic downland landscape). The new building is the start of every visitor’s journey to the Arboretum.

Discreetly set in a natural landscape hollow, it is deliberately modest in scale to minimise its impact on the historic landscape and to maintain the main focus on the collection of trees. Materials have been carefully considered; in response to its sylvan location, the building has been designed as an exemplar of the use of UK sourced timber and to demonstrate the aesthetics and capability of green materials in construction. In plan the building forms a gentle curve with an open colonnaded entrance space at its centre, giving views of the Arboretum beyond.

Once through the ticket barrier, the building’s facilities are available; toilets and mobility scooter storage on one side of the building and an information centre on the other side, where visitors can learn about the heritage and importance of Westonbirt’s world class tree collection, its management, and the wider role of the tree. The design of the building has been developed to deal with a variety of visitor levels and has the flexibility to allow the Forestry Commission to manage visitor flows.