Firefighters were called to the blaze on Woodgrove Ave just before 9am on Friday.
Fire and Emergency New Zealand shift manager Lyn Crosson said it thought the fire was suspicious and a fire investigator was assessing the scene.
Police are also investigating. A police spokeswoman said it was believed no-one was inside at the time.
A nearby resident told Starnews.co.nz they saw lots of black smoke coming from the house.
"They [Fire and Emergency New Zealand] were on to it straight away, but I tell you what, if they weren't that place would have burnt to the ground," the resident said.