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Underinsurance in UK Property Claims: What It Means for Your Claim
Rebuild Costs, Policy Wording and What to Check If Your Insurer Raises Underinsurance
Written by Darren Carter. Last Updated on October 12, 2026
When Underinsurance Becomes a Problem During a Property Claim
Underinsurance in UK property claims often becomes apparent only after damage has occurred. An insurer may say that the building, contents or other insured property should have been insured for a higher amount.
That can affect the claim. However, a proposed reduction should not be viewed as an automatic consequence of underinsurance.
The policy wording matters. So does the value the insurer believes should have applied, how that figure was calculated and how the original sum insured was established.
What Does Underinsurance Mean in a Property Claim?
Underinsurance generally means that the insured value is lower than the amount required under the relevant policy.
For buildings insurance, the important figure is usually the cost of reinstating or rebuilding the property. This is different from its market value.
Underinsurance can also affect contents, stock, machinery and other insured property. Businesses may have additional issues involving business interruption values and indemnity periods.
It can become relevant after a partial loss as well as a total loss. For example, an insurer may raise underinsurance following fire, flood, storm or escape-of-water damage even where only part of the property needs repairing.
When Does Underinsurance Become Relevant During a Claim?
An insurer may raise underinsurance after reviewing the insured values against its estimate of the property’s rebuild or replacement cost.
If this happens, ask the insurer to explain:
- The value it believes should have applied
- How that value was calculated
- The evidence or valuation methodology used
- Which part of the policy it is relying upon
- How any proposed claim reduction has been calculated
Do not assume that the insurer’s figure is necessarily wrong. Equally, a proposed reduction should be capable of being explained and supported.
Underinsurance can affect partial losses as well as total losses. It may therefore become relevant following fire, flood, storm, escape of water or other insured property damage, even where only part of the property needs repairing.
Underinsurance for Homeowners, Landlords and Businesses
Homeowners
For homeowners, buildings underinsurance often centres on the difference between the building sum insured and the estimated reinstatement cost.
Where consumer insurance rules apply, the information requested when the policy was arranged or renewed may also be relevant. This can include how the rebuild figure was established and what information or guidance was provided.
Landlords
Landlords should consider the individual property and policy arrangement. Extensions, conversions, unusual construction and significant alterations can all affect reinstatement costs.
Where landlord contents or other property are insured, those values should also reflect the basis of cover required by the policy.
Businesses
Commercial insurance can involve several separate insured values. These may include buildings, plant, machinery, equipment, contents and stock.
Business interruption cover requires separate consideration. The insured financial values and indemnity period should reflect the circumstances of the business and the realistic recovery period following an insured event.
Why Underinsurance Can Develop
Underinsurance can arise for several reasons. Rebuild costs may change, property information can become outdated, or the original sum insured may have been based on an unsuitable figure.
Market Value and Rebuild Cost Are Not the Same
A property’s market value is influenced by factors such as its location, land value, demand and local property prices. Rebuild cost looks at something different: what may be required to demolish, clear and reinstate the building following serious insured damage.
Depending on the property, this may include labour and materials, demolition and site clearance, professional fees, building regulations, outbuildings and other relevant reinstatement costs.
This is why using a property’s purchase price or estimated sale value as a shortcut for its buildings sum insured can produce the wrong figure. A Rebuild Cost Assessment may provide a more property-specific estimate where a simple calculator is unsuitable.
Changing Rebuild Costs
Construction costs can change over time. Labour, materials, professional fees and regulatory requirements can all affect the cost of reinstating a building.
As a result, a sum insured that was appropriate several years ago may need reviewing. Index linking can help account for changes over time, but it may not correct a figure that was inaccurate when the policy was first arranged.
Property Changes and Outdated Information
Extensions, conversions, changes in use and significant alterations can affect the appropriate rebuild cost. Older valuations may also become less reliable if the property has changed since they were prepared.
Reviewing the buildings sum insured after significant changes can help reduce the risk of the property becoming underinsured.
How an Average Clause May Affect an Underinsured Property Claim
Some insurance policies contain an Average Clause. Where applicable, this may allow an insurer to reduce a claim in proportion to the level of underinsurance.
For example, suppose a property has an estimated rebuild cost of £500,000 but is insured for £400,000. That represents cover equal to 80% of the estimated rebuild cost.
If an applicable Average Clause operates on that basis, a £100,000 insured loss could potentially be reduced to £80,000.
However, this is only an illustration. It does not mean every policyholder who is 20% underinsured will automatically receive 80% of their claim. The policy wording, calculation and individual circumstances all need to be considered.
Some policies may also contain different methods, thresholds or tolerance provisions. For a fuller explanation, read our guide to how an Average Clause can affect an insurance claim.
Why an Underinsurance Reduction Is Not Always a Simple Percentage Calculation
The percentage calculation is only part of an underinsurance issue. You may also need to establish whether the relevant policy term applies, whether the insurer’s rebuild or replacement value is properly supported and how the original insured value was established.
For consumer home insurance, the Financial Ombudsman Service may also consider the circumstances in which the policy was arranged. Relevant factors can include the questions the insurer asked, the information or guidance provided, whether the policyholder’s answer was reasonable and whether the policy actually contains an Average Clause.
This does not mean that an underinsurance reduction will necessarily be incorrect. Instead, it means the policy wording, valuation evidence and circumstances should be considered alongside the calculation.
Commercial insurance can involve different policy terms and legal considerations. Business policyholders should therefore avoid assuming that guidance applying to consumer home insurance will automatically apply to their policy.
You can read more in the Financial Ombudsman Service guidance on underinsurance.
FAQs – People Also Ask:
What does being underinsured mean in property insurance?
Being underinsured means the insured value is lower than the amount required under the policy. This can affect a claim, but the outcome depends on the policy wording and circumstances. A proportional reduction should not be assumed unless an applicable Average Clause or other relevant policy provision supports it.
How do I know if I’m underinsured?
For buildings insurance, compare the current buildings sum insured with an appropriate rebuild-cost assessment. A calculator may be suitable for some standard properties, while unusual, listed, heavily altered or complex buildings may need professional assessment.
What happens if I make a claim and I’m underinsured?
The insurer may raise underinsurance during the claim and may propose a reduced settlement, depending on the policy wording and circumstances. Ask it to explain the insured value it believes should have applied, the policy term relied upon and how any proposed reduction has been calculated.
Does the Average Clause apply to contents or business interruption insurance?
It can apply where the relevant contents or business interruption policy contains an applicable Average Clause or similar provision. The wording and calculation can differ between policies, so check the relevant section rather than assuming the same approach applies to every type of cover.
How to Reduce the Risk of Underinsurance Before a Claim
Rebuild costs change over time, so an insured value that was suitable several years ago may need reviewing.
In August 2026, BCIS reported that its residential rebuild cost models had increased by an average of 4.9% in the year to January 2026. However, costs can vary between individual properties and different elements of construction. An average percentage should not therefore be treated as the correct increase for every property.
- Review the rebuild cost at appropriate intervals. Check the figure at renewal and after significant changes to the property.
- Do not use market value as a substitute for rebuild cost. The figures measure different things and can vary significantly.
- Review the property after alterations. Extensions, conversions, changes in use and significant improvements may affect reinstatement costs.
- Check what the insured value needs to include. Depending on the policy, this may include outbuildings, demolition, professional fees and other reinstatement costs.
- Review other insured property separately. Contents, equipment, machinery and stock may require their own appropriate values.
- Review business interruption cover where relevant. Businesses should consider both the insured financial values and whether the indemnity period remains realistic.
- Keep evidence of how important figures were established. Retain valuations, assessments and relevant information from policy inception and renewal.
For straightforward residential properties, an appropriate rebuild-cost calculator may provide a useful starting point. More complex, listed, unusual, high-value or substantially altered properties may require a professional Rebuild Cost Assessment.
What to Do If Your Insurer Has Raised Underinsurance
If your insurer has raised underinsurance or proposed applying an Average Clause, ask for the reasoning and calculation in writing before deciding how to respond.
Useful points to check include:
- What insured value does the insurer say should have applied?
- How was that figure calculated?
- What valuation or other evidence supports it?
- Which part of the policy wording is being relied upon?
- How was your original sum insured established?
- How has any proposed settlement reduction been calculated?
It can also be useful to review the policy schedule, full policy wording, renewal documents, previous rebuild valuations, details of property alterations and any correspondence about the sum insured.
Independent Loss Adjusters can provide free initial insurance claim advice where underinsurance has already become an issue. If underinsurance has been raised during a property claim, our insurance claims management service may be able to help you review the policy wording, available evidence and the insurer’s position.
Depending on the circumstances, we may be able to help by:
- Reviewing the relevant policy wording
- Reviewing the insurer’s underinsurance calculation
- Considering the valuation or reinstatement evidence
- Examining information relating to how the sum insured was established
- Identifying points that may require clarification or further evidence
- Communicating with the insurer or its representatives where we are appointed
We cannot guarantee that an underinsurance or Average Clause reduction will be changed or withdrawn. The position will depend on the policy wording, evidence and individual circumstances.
If the proposed reduction forms part of a wider disagreement about the amount offered, our guide to reviewing a low insurance settlement explains other points that may need checking.
Preventing Underinsurance Before a Future Claim
If no claim has occurred and you are concerned about the buildings sum insured, the appropriate next step may be to review the property’s rebuild cost.
Our Rebuild Cost Assessment guide explains the difference between a simple calculator and a professional assessment. It also covers some of the property features that can make a more detailed valuation appropriate.
Where specialist valuation support is required, Exactum provides BCIS-based Rebuild Cost Assessments for homeowners, landlords and commercial property owners and is regulated by RICS.
A Rebuild Cost Assessment cannot guarantee how an insurer will deal with a future claim. However, it can provide clearer evidence when setting or reviewing the buildings sum insured.
Darren Carter
Head of Marketing & Technology, Independent Loss Adjusters
Posted by Darren - Over 15 years' experience in online marketing within the insurance claims sector and works with ILA's loss adjusters and claims professionals to turn practical claims knowledge into clear, useful guidance for policyholders.
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