Volunteer firefighters from Kawakawa and Towai were called to Tipene Rd, Motatau, about 1.15pm on June 7 after neighbours raised the alarm.
It is thought the house was almost complete but not yet occupied.
The house was half an hour's drive from Kawakawa fire station so the volunteers had little chance of saving it.
Firefighters on the second truck had to use chainsaws to cut up a tree that fell across Matawaia-Maromaku Rd in a storm, blocking the route to the blaze, after the first truck had passed.
The fire was soon deemed suspicious given the lack of a power supply or other ignition source, and threats that had allegedly been made to burn the house down.
The two accused are understood to be related to the homeowner.
In the Far North so far this year at least 10 dwellings, most of them in and around Ahipara, have been destroyed by arson.