Mace has beaten off competition from Bovis Lend Lease and Balfour Beatty’s Heery International subsidiary to win a £100m extension to the British Museum in London.

Mace has been appointed to construction manage Rogers Stirk Harbour + Partners’ North West Development scheme, which will involve a science and conservation centre, temporary exhibition galleries and storage space.

The consultation and design process for the North West Development are under way, although a planning application has yet to be submitted. The scheme, which is the first phase of a 20-year masterplan to upgrade the museum, is due for completion in 2011 or 2012.

Zoe Hancock, the museum’s director of projects and planning, said: “There’s still some way to go in the design and planning process, but it is a complex project and a complex site, and Mace’s early involvement will be of great benefit.”

The Great Court was a landmark project for us. To be invited back is an honour

Gareth Lewis, Mace

The expansion is necessary because the popularity of the museum has begun to outstrip its capacity. When completed, the extension will allow more of the museum’s collection to be displayed and increase visitor capacity from 5 million to 6 million a year.

Mace acted as construction manager on Foster + Partners’ Great Court project at the museum, which was also worth £100m. That involved installing a glazed roof over the central courtyard and restoring its reading room. It was completed in December 2000.

Gareth Lewis, a director of Mace, said: “The Great Court was one of our landmark projects. To be invited back to work on the museum’s next major construction project is an honour.”