There's all sorts behind brick exteriors! Some houses are prefabricated wood, or molded concrete slabs. Some are blockwork and others are double skinned brickwork.

If you want to build a house/renovate it etc, then your local council will have regulations on construction. In some areas it's acceptable and perfectly safe to have brick or concrete construction, where other areas require wooden structures due to earthquake activity.

NZ building regs are very different from area to area. Here in the Waikato, there are many different councils, such as Hamilton City, Waikato District, Waipa District, Matamata-Piako and so on, each with different building regulations. In some places you even need permits to move earth around in your own garden.

The answer to any building question is: Consult your local council first.

Drawbacks of the wooden houses are usually high maintenance, meaning having to be painted quite often, and the foundations being piles, which need replacing after a while. Damp can also be an issue in some older homes, which may require recladding to avoid some potential health risks. Make sure when you look at buying, that you get the building inspected by someone who performs moisture penetration tests on the walls.