Vs Natural homes the Christchurch earthquakes

Natural homes are designed to include reinforcing like steel rods or timber to make up for their lack of tension. Without it, while they are strong in compression (downwards pressure), they can be moved sideways by very high winds or the lateral pushing force of an earthquake.

“By adding reinforcing into buildings we overcome that inherent weakness and we can make buildings that are earthquake resistant,” says Graeme.

In the 1980s and 1990s, Graeme led a group of pioneers from the Earth Building Association to come up with the official NZ Standards which most earth buildings are now built to, creating the most comprehensive earth building standards in the world says Graeme. Straw bale is yet to get its own standards.

But when you live in a seismic country, there is always room for improvement so after the Christchurch earthquakes, EBANZ undertook a reconnaissance of some of the modern earth homes in the area built to the NZ Standard.

“They all came through fine. It was a good test of our standards, they’ve had nearly 20 years of service and proved to be very good,” says Graeme. “One or two had problems because the ground had moved – the building was absolutely fine but there was a 150mm slope across it.

“At the moment we in the process of revising the standards… we’ve imposed a few more restrictions on what can be designed without an engineer. After the Christchurch earthquakes, it wasn’t so much what we saw in earth buildings but what we saw in other masonry buildings. Some areas of buildings were just too vulnerable to leave to people without engineering calculations.”

Gable ends – the triangle end of buildings – were a concern.

“Just about every one popped out of buildings in Christchurch. We thought that will happen in earth buildings too if we’re not careful so we put in a few more restrictions about them.” ■