The Landmark Trust has funding for Llwyn Celyn farmhouse in Monmouthshire, with the aim of restoring its 500-plus years of architectural legacy.
The Grade 1 Listed medieval hall house is considered the most significant inhabited "at risk" building in Wales.
Welsh heritage body Cadw and the National Heritage Memorial Fund (NHMF) gave grants totalling Â£670,000.
Thought to date from around 1480, the property is said to represent key developments in Welsh architecture between the 15th and 18th Centuries and a textbook example of the development of the British manor house.
Largely untouched for the past century, the house is in more than six acres (2.6 hectares) of ground, near Llanvihangel Crucorney in the Llanthony Valley, and still has smoke-blackened roofs from its early years - the chimneys and floors were added in the 17th Century.
Jennifer Stewart, of the NHMF, said the aim of the work was to "build up the story and the story book of who lived in the property at different stages".
She said: "Because it has been in private hands for 100 years, we really don't know that much about it.
"Unlike modern houses, we don't know what is behind the panelling. We want to see what this house is like inside and what it was like to live in this house. There's a huge amount to be discovered there."
However, it is thought that the original owner must have been someone of considerable status and wealth and there is possibly a connection with Llanthony Priory which is situated less than six miles away.
The Landmark Trust is to begin fundraising for the restoration and the house, which sits within the Brecon Beacons National Park, will be available for rent as holiday accommodation.
SOURCE: Cadw
Ms Stewart added: "Often the way to preserve [buildings like this] is to find them a use. This is an other way to find a modern use for an ancient building.
"This is helping the building to "breathe" if you like. If people have enjoyed their stay, they may well provide additional funds."
Peter Pearce, director of the Landmark Trust, said: "The importance of Llwyn Celyn in helping us understand the development of high status Welsh houses more fully cannot be understated."
It may not look like much now, but this in-need-of-attention property is set to be a holiday let for history fans.