The move will see the neo-Georgian building, Northcote House restored and the surrounding land redeveloped as a retirement village providing 103 apartments for people aged over 55.
The site will also see the development of 168 new homes.
Northcote House was sold to the Government in 1947 and was used as a training centre for civil servants until 2012. In recent years, the building had been used as a conference centre and hotel.
Berkeley Group Chairman, Tony Pidgley said: “We are delighted to be moving ahead with this exciting project and look forward to working with the Royal Borough of Windsor and Maidenhead and local people to create a fantastic community at Sunningdale Park, alongside a beautiful new 42 acre public park for everyone to enjoy.”
The retirement village will be built by the Audley Group.
Nick Sanderson, the Chief Executive of the Audley Group said: “This site presents a unique opportunity to create an aspirational mixed use development to serve the whole community.
“The demand for high quality retirement living options, with a holistic approach to housing, care and health, continues to grow and we’re proud to be leading the way.”