Is Your NZ Home Underinsured? The Hidden Risk Affecting Thousands of Kiwis

The Underinsurance Problem in New Zealand

Underinsurance is one of the most widespread and underappreciated risks facing New Zealand homeowners. The problem is simple: you insure your home for less than it would actually cost to rebuild it. When disaster strikes, your insurer pays out up to your policy limit — and you cover the rest yourself.

After major events like the Canterbury earthquakes and Cyclone Gabrielle, assessors discovered that a significant proportion of affected homes were insured for substantially less than their true rebuild value. Some homeowners faced rebuild shortfalls of $100,000 or more — money they had to find themselves at the worst possible time.

Why Underinsurance Happens

Most homeowners don't deliberately underinsure their properties. It happens gradually, through a combination of common mistakes:

Setting and forgetting: The sum insured is set when the policy is first taken out and never reviewed, even as rebuild costs rise with inflation
Using the purchase price: The market value of a property includes land — which is not insured. Your buildings insurance only needs to cover the rebuild cost of the structure, but many people use their purchase price as a starting point, which may be too high in some cases and dangerously low in others
Not accounting for construction cost inflation: NZ construction costs rose sharply through 2022–2024, driven by supply chain disruption, labour shortages, and material price increases. A sum insured set in 2020 may be 25–35% too low today
Forgetting permanent improvements: Renovations, extensions, new kitchens, and landscaping all add to the rebuild cost but are often not reported to the insurer
Ignoring site-specific costs: Demolition, debris removal, professional fees (architect, engineer, surveyor), and compliance with current building codes all add to a rebuild — sometimes by 15–20% above the raw construction cost

What Is the Rebuild Cost?

The rebuild cost — also called the replacement cost — is the amount it would cost to demolish the existing structure and rebuild your home to its current standard from scratch, on your existing site, using today's material and labour costs. It is not the same as:

The market value of your property (which includes land)
The rateable value (RV/CV) set by your local council
The price you paid for the property
What a neighbour's property sold for

The rebuild cost depends on the size of the house (floor area in m²), construction type (timber frame, brick veneer, concrete block, etc.), quality of finishes (standard, mid-range, premium), location (regional construction costs vary significantly), and any special features (pool, workshop, sleepout, deck, retaining walls).

How to Calculate Your Rebuild Cost

Option 1: Use the Cordell Sum Sure Calculator

The Cordell Sum Sure Calculator — developed by CoreLogic and widely used by NZ insurers and brokers — provides a free, reasonably accurate rebuild cost estimate based on your property details. It takes around five minutes to complete. While not a substitute for a professional valuation, it is a reliable starting point and is widely accepted by insurers as a reasonable basis for setting sums insured.

Option 2: Use a Quantity Surveyor or Registered Valuer

For high-value, unusual, or heritage properties, a professional insurance valuation from a registered valuer or quantity surveyor is the most accurate approach. Expect to pay $400–$1,500 depending on the property. This valuation should be updated every three to five years, or sooner following significant renovation.

Option 3: Review Your Insurer's Rebuild Cost Estimate

Some insurers provide their own estimate of your rebuild cost at renewal. Review this figure carefully — if it seems low relative to your understanding of current construction costs, query it with your adviser.

The Proportional Payout Problem

Some buildings insurance policies contain an "averaging" or "co-insurance" clause. If you are insured for less than the full rebuild cost and you make a claim — even for a partial loss like a damaged roof — your insurer may only pay a proportional share of the claim.

For example: your home has a true rebuild value of $700,000 but you are insured for $500,000 — 71% of the actual value. You make a $100,000 claim for storm damage. With averaging applied, your insurer may pay only 71% of $100,000 — just $71,000 — leaving you $29,000 short, plus your excess.

Not all policies apply averaging clauses, and some apply them only after you are more than a certain percentage underinsured. Ask your adviser whether your policy includes this clause and how it works.

Construction Costs in New Zealand: 2024–2026 Context

According to CoreLogic and BRANZ data, New Zealand construction costs rose an average of 7–10% per year between 2021 and 2024. While cost inflation eased in 2024–2025 as supply chains normalised, overall construction costs remain 30–40% higher than pre-2020 levels. This means a home insured in 2019 based on 2019 cost estimates is likely significantly underinsured today, even if the policy has had annual CPI adjustments applied.

Labour shortages, particularly for tradespeople, continue to put upward pressure on rebuild timelines and costs. After a major event like an earthquake or severe weather, when many properties are damaged simultaneously, rebuild costs typically rise further due to demand pressure — a phenomenon insurers call "demand surge."

How to Fix Underinsurance

Run a Cordell Calculator estimate for your current property details
Compare the result to your current sum insured — if there's a significant gap, contact your insurer or broker
List all permanent improvements you've made since the policy was set
Ask your adviser about inflation-linked sum insured options — some policies automatically adjust the sum insured annually based on construction cost indices
Set a reminder to review annually, ideally at renewal time

Getting the right sum insured is one of the most important things you can do as a homeowner. Speak with one of our advisers — they can help you assess whether your current cover is adequate and identify the best policy for your property.