Chief fire officer Garth Campbell said fire crews were called to the fire at about 6.20pm and by the time they arrived the house was "fully involved" and "was a difficult fire to get back under control."
He said the chimney fire had quickly progressed into the ceiling space and roof cavity and the A-frame house "didn't make for an easy fight."
St Johns ambulance attended the scene but there were no injuries.
It is understood the house belonged to well known Wanaka mountaineer Geoff Wayatt and his wife Beryl who were in the house at the time.
Chief officer Campbell said there would have been a lot of mountain climbing and rescue memorabilia and personal items in the house.
He said Mr Wayatt had been a member of the Wanaka LandSAR and was a "good community person" .
