Building: Castle extension, Couston, near Aberdour, Fife

Architect: Morris & Steedman Architects

Stone type: Clashach columns and flooring; hand-cut roofing slates from Easdale in Argyll

Construction type: Loadbearing columns

A common approach when extending a historic structure is to replicate the form and construction of the original, but at Couston Castle, the architects Morris and Steedman opted instead to make a clear distinction between the previously-restored tower house dating from the 15th century and its 21st century addition. The design of the new extension draws on historical sources for its inspiration, most notably the loggia built in the early part of the 20th century at Dunderave Castle on Loch Fyne by Sir Robert Lorimer.

The owners of Couston Castle desired additional ground floor accommodation which would provide better views across the loch than those available from the small windows in the tower, and the new extension is constructed on the site of a former walled garden to be only 10 metres from the water’s edge. The modern, light-filled garden room is accessed from the tower’s kitchen and uses stone and slate to echo the wall and roofing materials of Scotland’s traditional architecture.

The horizontal emphasis of the extension’s design contrasts strongly with the verticality of the tower and in this wholly contemporary structure the design of the glazing capitalises on the views to the landscape beyond whilst the glass itself is effectively rendered invisible. The new extension appears simple but its unframed glass panels are detailed to check into the stone columns in order to maintain clarity between solid and void. The round columns are fitted around steel rods and are formed from 60 semi-circles of oxide-veined Clashach sandstone.