The small rural home in Glenore, about 10km from Milton, was fully involved by the time fire crews arrived about 3pm.
Five crews battled for about an hour to bring the house fire under control.
A Fire and Emergency New Zealand (Fenz) spokesman said crews from Milton, Lawrence, Waitahuna and Balclutha attended the incident on the Manuka Gorge Highway (State Highway 8).
The single-storey 20m by 20m dwelling was located up a long drive on a hillside section surrounded by trees.
It could be seen burning from the highway, and a plume of black smoke was visible from several kilometres away.
By 5pm the blaze was under control, but had ''almost half-destroyed'' the house, Fenz said.
A digger had been requested to remove roofing iron from the embers and allow further damping down to take place.
A fire investigation officer had been summoned to determine its cause.
The homeowner was at the scene being comforted by friends, and declined to comment.
