Thousands of buildings need to be demolished and rebuilt or repaired due to damage caused by the Christchurch earthquake, a new report shows.
The Earthquake Commission's Stage 2 geotechnical report assessed the quake damage to 22,500 properties around Canterbury.
It classified 3,300 properties as 'Zone C', meaning they have suffered major damage from land liquefaction and shaking.
Many of those properties will need to be completely rebuilt or undergo large scale repair work, the report states.
It also describes how the cracked and shifted land around the damaged houses could be stabilised.
"Zone C is the land which has generally suffered very severe or major land damage, or is close to the areas of major remedial works."
"In these zones a more coordinated and strategic approach is recommended to repair the land and to allow more robust reconstruction of buildings and infrastructure."
Houses on the banks Avon River in Christchurch were hit hard by the quake, the report shows.
They suffered heavy damage from the soil near the river liquefying and shifting their foundations.
Large area of the suburbs Burwood, Dallington and Richmond are classified as severely damaged.
Widespread land liquefaction also hit dozens of houses in North and South Kaiapoi.
The first repairs to the significantly damaged 'Zone C' houses are expected by August 2011.
Repairs to the 19,200 'Zone A' and 'Zone B' properties with minor or moderate are able to start now, the report states.
Some "older, well established" are not covered by the report's recommendations, as it would require what is described as impractical and unnecessary large scale demolition.
Earthquake recovery minister Gerry Brownlee said the report gave new certainty to Canterbury homeowners.
"For the majority of property owners, the recovery process is relatively straightforward and the repair process can start now."
Mr Brownlee urged Cantabrians to lodge damage claims with the Earthquake Commission before a cut-off date on Saturday.
Information packs about the Stage 2 report, including "individualised" letters, and a fact sheet on the claims process, were yesterday posted to Canterbury residents who had lodged claims before November 19, he said.