The Torwoodlee Estate spreads across 3,000 acres (1,200 hectares) in the Scottish Borders.
Improvement works have been carried out to the rest of the building over the years but the east wing has remained largely untouched since the 1980s.
Now an upgrade will take place including removal of internal partitions to enlarge existing living space, and moving both the kitchen and ground floor bathroom, while adding a first floor shower room.
The building was described – most likely in the local press in the late 18th Century – as a “magnificent barn” due to its “pretty square-looking design”.
Its east wing has been derelict for decades but will now be restored to a liveable space.