A trust has taken over the running of a 19th Century listed building from Somerset County Council.
The licence, issued to Hestercombe Garden Trust, will help Hestercombe House to become a national centre for landscape and conservation studies.
Cabinet member, David Huxtable, said: "It will be great to see part of our Somerset heritage fully restored and thriving once again."
The Trust will seek heritage lottery funding for the development project.
The county council bought the house in 1977 for office space and the trust owns the surrounding landscaped gardens.
Devon and Somerset Fire and Rescue Service also lease a section of the building but this is due to expire in October.
The council said moving the house to the trust's control had the advantage of removing the "heavy potential liability" and having to pay for ongoing maintenance.
"There are lots of planning restrictions by the district council and a listed building to boot, so quite huge liabilities," said Mr Huxtable.
"Although a nominal value of £900,000 has been put on it by the district valuer, we thought the best deal for the county council was to divest ourselves of it and give it to the trust to use it as collateral to bid for National Lottery money."
Once the revamp is complete, the house will be opened up to the public and free access will be given to Somerset residents in the first two years after the refurbishment.
Chief executive of the trust, Philip White, said: "We want to restore the main rooms to something approaching the original designs, and then allow the public into the house so they can see the gardens from inside the house, which is the way they were meant to be seen."