Have the Christchurch earthquakes altered foundation design?

The Christchurch Earthquakes that have persisted since 2010 have provided New Zealand with a unique oppertunity to examine the structural performance of New Zealand building designs both in the main quake and during the multiple aftershocks. Unfortunately traditional slab construction was the poorest performing foundation system. Foreshadowing changes to the New Zealand Building Code, the immediate response from New Zealand's Department of Building and Housing has been to recommend ribbed raft waffle slabs as a preferred alternative for domestic and light commercial construction.

“Encouraging wide, stiff foundation systems such as stiff rafts eg, waffle slab…is considered to be the best way of improving performance”

"An observation from the Canterbury earthquake is that there are significant advantages in people being able to remain in their homes for as long as possible after the event. This means employing building practices to limit the damage so that buildings remain habitable and ultimately gain a Green (Inspected) placard from council. Encouraging wide, stiff foundation systems such as stiff rafts (eg, waffle slab) or stiff inter-connected footings is considered to be the best way of improving performance with respect to both amenity and collapse, and thereby improving homeowners’ confidence in repairing or rebuilding these locations."

Download the full document <guide-canterbury-earthquake.pdf>