The house was due to be receiving earthquake damage repair in two weeks, fire investigator Kelvin Hampton said.
The cause of the blaze remains undetermined, although witness statements are consistent, Mr Hampton said.
"From the point of view of the Fire Service, I would suggest to anyone in the similar situation of discovering an early fire to think very carefully about risking their safety to attempt to extinguish it.''
"A house is property and human life is way more important,'' he said.
"In the time it takes you to go away and get a pot, a fire can get a lot bigger by the time you get back.''