Firefighters from Alexandra and Clyde were called to Jackson Pl, in Alexandra, about 7.50pm, and arrived to find a house "well involved in fire'', a Fire and Emergency New Zealand spokesman said.
Two fire appliances from Alexandra attended initially, but they called in an additional appliance from Clyde, together with a support vehicle, after arriving at the scene, the spokesman said.
It was unclear whether the occupants were at home at the time of the fire, but there were no reports of injuries.
The house was believed to be extensively damaged, but the cause of the fire was also not yet known, he said.