Ngunguru Chief Fire Officer Chris Gibbs said the fire started in a bedroom.
Everyone managed to get out safely and one person was taken to hospital to be treated for smoke inhalation.
Special fire investigator Craig Bain said the blaze was caused by an electrical fault within the wall cavity.
"They were very lucky to get out," he said.
There were three people home at the time of the fire - Mr Browning's mum, his friend Dan, who was boarding with her, and Mr Browning's nephew. He said his mum had rented the house for four years.
"Mum was out on the lawn [last night] devastated."
Yesterday Mr Browning and a group of about nine friends and family spent the day shovelling through the ashes trying to save what they could.
"We're looking for mum's jewellery and all the sentimental stuff."
Mr Browning said they tried everything to help contain the fire.
"Dan tried to use the fire extinguisher, it was all up the wall so we tried putting the hose in the window."
Despite the devastating fire the group still managed to retain a sense of humour.
"What was funny is Dan slept butt naked so he was running around with a naked bum in front of mum," said Mr Browning.