Six fire crews have spent the night tackling a blaze in the Dartmoor village of Cheston.
The intial call, received just after 8pm on Saturday, reported a chimney fire at the property, located between Wrangaton and South Brent.
But the caller then updated the fire service to say more of the building was ablaze.
Six crews spent nine hours extinguishing the fire, which had taken hold of the first floor of the property.
A spokesman for Devon & Somerset Fire & Rescue Service said it appeared to have spread unseen through the walls, with crews cutting away and using thermal imaging cameras to identify hotspots.
Fire and Emergency Support Services from the Red Cross attended the scene to offer welfare support to the occupants of the property.
By 5.15am only one fire engine remained at the incident.