More than 60 local groups, support and government agencies and building companies are involved in the weekend event at the CBS Arena.
The primary focus is to give the public the latest information on rebuilding the city, and on insurance and home repair issues.
But community-run groups are also making their voices heard, such as an organisation representing people who own the potentially most unstable green-zone land.
The TC3 group says it has 1600 members whose homes were badly affected in the earthquakes, many of whom are still waiting for repairs.
A representative, Maria Thackwell, says it's important to have a presence at the expo because the Government is not listening to them and is not talking to grass-roots people.
Public seminars are being held on issues such as rebuilding on TC3 land and what homeowners should know when making repairs to their houses. The expo is also hosting panel discussions with insurance company representatives.