Donald Insall Associates has been named conservation architect for a major overhaul of Grade I-listed Wentworth Woodhouse near Rotherham, South Yorkshire
The studio defeated an undisclosed shortlist to win the publicly tendered Historic England contract worth around £650,000.
The appointment comes three months after the practice was chosen to work alongside BDP on the multi-billion restoration of parliament.
The practice will oversee a major restoration of the crumbling 23,000m² Baroque country house, which features a 185m façade and is thought to be the largest private dwelling in the country.
Planned to complete in 2020, the phased project is backed by Woodhouse Wentworth Preservation Trust which purchased the enormous 18th-century complex earlier this year.
Donald Insall Associates chair Tony Barton said: ‘Our team can’t wait to make a start and we look forward to helping secure the future of this very special building. The full range of our technical, creative and analytical skills will again be applied at Wentworth Woodhouse.’
The latest project is divided into two phases with the first element covering essential roof and external repairs to the south-east wing and nearby riding school. The second phase will repair the main 19-bay east façade along with the chapel, oak staircase and grand staircase. Repairs to the floors and ceilings of the long gallery, and the south-east and the north-east pavilions will also be included.
Wentworth Woodhouse was built by several architects between 1725 and 1750 for Thomas Watson-Wentworth, marquess of Rockingham. It features around 365 rooms, 1,000 windows and several kilometres of underground passages.
Its 73ha estate was used as a teacher training college during much of the 20th century, and its most recent owner was the architect Clifford Newbold who planned to transform it into a £200 million spa.
Woodhouse Wentworth Preservation Trust purchased the building in March. It plans to open it to the public and create an events space in the north wing. The stables will be converted into offices and a small number of residential, short lease units will also be created.