Vs Nat­u­ral homes the Christchurch earth­quakes

NZ Lifestyle Block - - Feature -

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.” ■

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