"From the exterior, the wooden house looks intact, but the interior is pretty much destroyed," Mr Rush said.
An exterior wall and the roof area of the house next door were also damaged.
Mr Rush said the incident provided an important reminder to check all electrical equipment.
"Heaters, extension cords and fans should all be checked to make sure they are working and safe."
The recent fire at Utiku in north Rangitikei, in which 28-year-old farm worker Hamish Allen died, was caused by a faulty heater, Mr Rush said.
Last night the two fire teams were at the house for up to four hours, dampening down hot spots.
"It is old timber and the fire gets deep-seated in the timber."