The likely result of this change is that many will be under-insured - whether by design or accident. And the insurer will no longer foot the bill.
"The idea of sum insured is really terrifying, particularly for people in Canterbury, because you can never have enough information," says the relationships manager for community network Cancern, Leanne Curtis.
"We've been unfailingly trusting that we pay insurance and the insurer pays us out. This has shown people really don't know their policies and, even if they do, the insurer can make changes after the event.
"So many things are hidden. Don't even begin to expect that what you sign for and what you get are the same thing."
The new system requires homeowners to specify the sum insured - the maximum the insurer will pay if their home needs to be rebuilt or extensively repaired. To be fully covered, they'll need to factor in not only construction and material costs, but architect, planning and consent fees, the cost of demolition and removal of debris.
These costs, particularly repair and replacement, are notoriously uncertain and subject to rapid rises The sum insured will have to rise annually to keep pace, as will the premium.
Premiums were already rising, and the industry is making other changes, including higher excesses and limits on payments for retaining walls and "recreation features" such as tennis courts and swimming pools.
Insurance Council operations manager Terry Jordan says reinsurers have realised New Zealand is a high earthquake risk country and full replacement cover left them over-exposed.
Most homeowners in standard homes can expect small premium increases, Jordan says, "but where people have matai flooring or Italian slate tiles and granite benchtops they will be assessed on their property rather than the average for the region.
"Christchurch has changed the world as we know it. Insurers have told us it's the most complex natural disaster ever."
But Auckland insurance lawyer Andrew Hooker says the basis for the change is spurious.
"Why should I pay more for my premium because of Christchurch? Insurance is about risk so when I insure my house what is the risk of fire or natural disaster?"
Hooker says earthquake risk in northern New Zealand hasn't changed because of Canterbury or this week's Cook Strait quakes.
The change has been well-flagged by the industry, and insurer websites have detailed explanations and an online calculator to help homeowners estimate their cost of rebuilding. But critics say the transition remains a soft-sell and many homeowners will be caught out if disaster strikes.
"Insurers are presenting it as very simple and 'trust us'," says Curtis. "I don't think they've put enough education and support in place."
The Australian Cordell rebuilding cost calculator, adapted for New Zealand conditions, is accepted by the industry and mortgage lenders as tolerably accurate for the average home, but it is less reliable for architecturally designed, high-spec homes and properties with special features or on challenging sites.
Curtis and others warn that to get a fair deal, homeowners will need to do a lot more homework - and not rely on the calculator.
"Unless people get qualified quantity surveyors in, they are going to miss something," Curtis says. "A bigger concern is that people don't really understand enough about what their insurance covers."
Insurance ombudsman Karen Stevens says homeowners will have to think hard about the features of their home and the replacement costs.
"There are an awful lot of issues to get their heads around and it's up to them to do it."
Stevens says some Christchurch owners with sum-insured policies found they were woefully under-insured. The new system may give less wriggle-room for insurers but it's a double-edged sword: "The sum is the sum - it provides certainty but what is the cost of that certainty?"
She says disputes have arisen over policy wording and technical meanings. Some with full replacement cover have lost because their policy had incorrectly recorded the size of house and the insurer paid only for the square metres covered.
Disputes over rebuild materials are common. Homeowners expecting "like-for-like" replacement have found insurers specify lower-quality materials and features, such as replacing native timber flooring or panelling with particle board.
Most policies have clauses allowing replacement with "materials in common use", frustrating owners of older villas and bungalows.
Christchurch has also highlighted the hidden costs in slab foundations and underground services.
Lending institutions are concerned that mortgage-holders are adequately insured under the new system.
ASB Bank's head of insurance products Craig Haycock says borrowers can expect gentle reminders if the bank feels their insurance has slipped significantly below replacement cost.
"It doesn't heighten the risk about lending but it has heightened our focus to ensure customers adequately insure their property."
Philip O'Sullivan of building consultancy Prendos says a valuer's assessment - costs start at around $400 - should be sufficient guide for most homeowners, but more complex properties will require a building or quantity surveyor.
He expects most owners to weigh up the cost of an assessment and likely higher premiums against the risks of being under-insured.
But he warns that hidden costs in repairs are often not revealed until they are fully investigated.
"Christchurch shows that costs have been highly under-estimated."
geoff.cumming@nzherald.co.nz
