The former headquarters of Powys Teaching Health Board at Bronllys near Brecon, would include five-star accommodation, with over 40 en-suite bedrooms and a new Ball Room.
Bronllys Hall, would create new employment, business and economic opportunities in the area, Hughes Architects says.
It will put in a planning application next month for the venue which could host private, corporate and public events from weddings to conferences.
A 28-day pre-planning consultation is underway.
Doug Hughes, managing director of Hughes Architects, said: “This is a significant investment to restore and enhance Bronllys Hall to its original architecture as a private house in early Victorian times. The former Mansion House has dilapidated over time having been boarded up for the past four years since becoming surplus to the requirements of the previous owner.”
Elements included in the restoration and improvement of the Hall will be the creation of a new Ball Room, restoration of the main house function rooms, and creating keep-fit and spa facilities. The historic ‘Victorian’ and ‘Walled’ gardens are to be restored .
The history of the property dates back to around 1500 when the Duke of Buckingham is recorded as being the owner of the estate. It has had some other notable owners and redesigns over the centuries before being sold in 1913 to the King Edward VII Welsh National Memorial Association. King George V opened the Mansion House as a TB sanatorium in 1920.
It returned to private ownership earlier this year when the conversion concept, planning and internal renovations began under the management of Bronllys Estates Ltd.
“Our vision is to bring back and sympathetically extend a spectacular and well-known building to its original glory, creating employment and associated inward investment, not only into the immediate local area but for the whole of Mid Wales as a region,” said a spokesperson for Bronllys Estates Ltd.
“Above all, we intend to restore and enhance Bronllys Hall, it having come close to becoming uneconomic to repair through dilapidation. It has significant historical value to the area and can help bring even more economic opportunities, including jobs.”
Details of the pre-planning consultation can be found at www.hughesarchitects.co.uk.