The government says exceptions are impossible.

Sparing individual homes within Kaiapoi's condemned red zone is not an option because fixing the land requires an area-wide solution, the government says.

Last week Kaiapoi couple Brent and Shirley Cairns spoke to theSunday Star-Times about their battle to save their home and business, which has been condemned by the government because it sits in the middle of a residential red-zone. They believe their land, which shows no visible signs of damage, can be rebuilt on and therefore they should be allowed to stay put.

A week ago a protest rally they organised in Kaiapoi attracted around 200 people who are also upset by the prospect of having to walk away from their homes.

But the government said a mass exodus was the only viable option.

Commenting on the Cairns' situation, a spokesman for Earthquake Recovery Minister Gerry Brownlee said regardless of what the couple believed about their land, it was in an area prone to liquefaction and which had suffered significant damage.

"The Cairns might feel their land is not badly damaged but the geo-tech engineers say otherwise," the spokesman said.

If the government had decided to spend money on fixing the land, the Cairns and others in their situation would have had to move out of their homes for at least five years while the work was done.

Advice from geo-tech engineers was that, with modern foundations and building techniques, a property required at least 1.5m of firm ground, known as the crust, over any liquefiable material to be able to adequately support a residential dwelling. In Kaiapoi North, where the Cairns live, the crust thickness ranged from 20cm at its thinnest to 1m at its thickest.

"The majority of the land in the area ranges from 40cm to 70cm. None of the land in the Kaiapoi North is the required 1.5m thick, which means remediation of that land would require the removal of all houses followed by repeated addition and compaction of soil and stone, among other treatments," the spokesman said. Water and waste pipes would have to be removed and replaced.

"The cost of this far exceeded the cost of buying every house and section in the area at 2008 rating valuation ... and the work would have taken at least five years."

The government buy-out package, which gives people in the red zone the choice of either selling their land and house to the government (known as Option 1) or of selling the land to the government and negotiating a price for the house with their insurer (known as Option 2), were the only viable alternatives and gave people the chance to move on, the spokesman said.

Canterbury Earthquake Recovery Authority (Cera) chief executive Roger Sutton said about 378 property owners had indicated they wanted to chose Option 1 and 563 had chosen to go with option two.Those in the red zone have nine months from the date they receive their offer letter to chose an option; so far only around 900 have made a decision.

At the same time around 300 property owners had requested to have their land re-zoned.

"There's 286 people who are currently green, who want to be orange or red, and there's 26 who are red who want to be orange or green," Sutton said.

Under the zoning system, areas that are red are condemned, areas that are orange require further evaluation, and areas that are green are safe to rebuild on.

- Sunday Star Times