Civil Defence Minister John Carter says an estimated 100,000 houses were damaged by the earthquake on Saturday.
He says it's not clear how many of these are unliveable as a result.
The known number of houses in the Waimakariri, Selwyn and Christchurch areas is 160,000.
Mr Carter says it could be a week before a full assessment of all the damaged houses, is completed.
He says welfare centres will remain open for as long as they are needed and alternative accommodation may be considered.
Prime Minister John Key says it's not yet clear how many of the damaged houses are uninsured; the national average is 5%.
He says the Government has to tread carefully with the uninsured because it has to send the message that homeowners must have insurance.
But, he says, it will be treated on a case-by-case basis.
Most Housing NZ tenants secure
About 650 of Housing New Zealand's 6000 homes in the Christchurch area have been affected by the quake.
More than 200 state houses are being assessed for damage by engineers and some of those will have to be demolished.
Housing New Zealand's chief executive, Lesley McTurk, says however that not many tenants have had to leave their homes.
The agency has been checking on its tenants, she says, and taking elderly tenants to stay with friends and relatives.