The North Island is an active volcanic region, and while eruptions (and the earthquakes that often come before them) are rare, we can’t predict them.
Homes can be damaged by falling ash, lahar (mudflows), pyroclastic flows (a flowing mass of hot gas and rock), landslips and fire.
Homes near an active volcano are most likely to be damaged but the wind can spread ash for large distances, causing damage to homes well away from the volcano.
The GNS Science website has information about how to deal with ashfall.(external link)