It consisted of a garage with an upstairs sleeping area and an attached workshop.
Kaikohe deputy fire chief Wiremu Matene said two appliances responded with crews staying until well after midnight.
The building couldn't be saved but firefighters made sure the blaze didn't spread to flats just a few metres away over the property's back fence.
After examining what remained of the building, fire investigator Michael Champtaloup said the blaze was most likely deliberately lit but he couldn't rule out accidental causes.
Kaikohe police made door-to-door enquiries in the neighbourhood yesterday and urged anyone with information about the fire to call them on (09) 405 2960 or Crimestoppers, anonymously, on 0800 555 111.
Meanwhile, a Kaitaia family had a lucky escape on Sunday after a child's battery-powered hoverboard ignited, setting fire to a wall, carpet and duvet.
The hoverboard's 13-year-old owner and her mother saw flames through the windows when they returned from fetching takeaways about 9.15pm.
They closed the door to stop the blaze spreading then fought the flames with a garden hose through a window until the Kaitaia Fire Brigade arrived.
Station officer Ross Beddows said the family "did everything right" and managed to limit the damage to one room.
The hoverboard, a self-balancing scooter powered by lithium ion batteries, had been used a few hours earlier.
"It was extremely fortunate that the fire started early in the evening, when the occupants were still awake. If it had been the middle of the night when they were asleep it may well have proved deadly," Mr Beddows said.
The owner's grandfather, who did not wish to be named, said the house had a smoke alarm but the battery had died.
His granddaughter had owned the board for two years and had taken it with her when the family flew to Dunedin last Christmas, although the airline had been reluctant to take it.
Many airlines now refuse to carry hoverboards because of their reputation for spontaneously catching fire.
