How Underinsurance Happens in Office Buildings (And How to Avoid It)

Introduction

Underinsurance is one of the most expensive surprises in commercial property claims. It happens when the declared value on your policy is lower than the true cost to reinstate the building and/or replace its contents. In office buildings, it’s especially common because costs change quickly, fit-outs evolve over time, and responsibilities can be split between landlord, managing agent, and tenants.

If you’re underinsured and suffer a major loss (fire, flood, escape of water, storm, malicious damage), the insurer may apply “average” (the underinsurance clause). That means your claim payment can be reduced in proportion to how underinsured you are — even if the claim is relatively small.

This guide explains how underinsurance happens in office buildings, the warning signs, and the practical steps you can take to avoid it.

What “underinsurance” means in office building policies

Underinsurance usually relates to one (or more) of these insured values:

• Buildings sum insured (reinstatement cost): the cost to rebuild the office building after a total loss, including professional fees and demolition/clearance.

• Contents sum insured: office furniture, IT equipment, fixtures, and sometimes tenant improvements (depending on the policy).

• Business interruption (BI) / loss of rent: the amount of gross profit or rental income you’d lose during the rebuild period.

The key point: market value is not the same as rebuild cost. A building in a prime location may have a high market value but a rebuild cost that’s higher (or lower) depending on construction type, specification, and current labour/material prices.

Why office buildings are particularly exposed

Office buildings have a few characteristics that make underinsurance more likely:

• Frequent changes: refurbishments, reconfigurations, new partitions, upgraded HVAC, and tenant fit-outs.

• Complex reinstatement: modern offices often require specialist systems (fire alarms, access control, lifts, air handling, comms rooms).

• Inflation volatility: construction inflation can move faster than general CPI.

• Split responsibilities: landlord insures the structure; tenants insure contents and sometimes improvements; managing agents arrange cover.

When multiple parties assume “someone else is handling it,” values can drift out of date.

The most common ways underinsurance happens (and how to avoid each)

1) Using market value instead of reinstatement cost

How it happens: A landlord or director uses a property valuation, purchase price, or estate agent estimate as the buildings sum insured.

Why it’s risky: Reinstatement cost includes demolition, debris removal, professional fees, and rebuilding to current standards. It’s not tied to sale price.

How to avoid it: Use a reinstatement cost assessment (RCA) from a qualified surveyor. Review it regularly (typically every 3–5 years, or sooner after major works).

2) Not accounting for professional fees and site clearance

How it happens: The sum insured is set to “rebuild the walls and roof,” but excludes:

• Demolition and debris removal

• Architects, engineers, surveyors

• Planning and building control costs

• Project management

How to avoid it: Ensure your buildings sum insured is based on a proper RCA that includes fees and clearance. If you’re estimating, build in a realistic allowance.

3) Construction cost inflation outpacing indexation

How it happens: Policies often apply index-linking, but construction inflation can exceed the index used, especially after supply chain shocks.

How to avoid it:

• Confirm what index is used for index-linking.

• Review sums insured annually at renewal.

• Consider a mid-term review if you’re in a high inflation period.

4) Major refurbishments not declared

How it happens: Office refurbishments are common: new reception areas, upgraded toilets, new flooring, LED lighting, air conditioning upgrades, glazing, lifts, or roof works. If the insurer isn’t told, the sum insured may be too low and the risk profile may change.

How to avoid it:

• Tell your broker/insurer about planned works.

• Update sums insured after completion.

• Check whether the policy requires notification of works above a certain value.

5) Tenant improvements and “who insures what” confusion

How it happens: In multi-let buildings, tenants may install partitions, kitchens, comms cabling, or specialist fit-outs. Sometimes the lease says the landlord insures the structure, but it’s unclear whether tenant improvements are included.

How to avoid it:

• Review the lease and schedule of dilapidations responsibilities.

• Clarify whether tenant improvements are insured under the landlord’s policy or the tenant’s.

• If the landlord policy includes them, make sure the buildings sum insured reflects it.

6) Underestimating the cost of compliance and “betterment”

How it happens: After a major loss, you may need to rebuild to current regulations (fire safety, accessibility, energy efficiency). Older office buildings may require upgrades that weren’t part of the original construction.

How to avoid it:

• Discuss compliance costs with your broker.

• Ensure the policy includes adequate cover for increased cost of working and compliance-related reinstatement.

• Use an RCA that considers building type and likely compliance impacts.

7) Not insuring for the right reinstatement period (BI / loss of rent)

How it happens: A landlord chooses a 12-month loss of rent period, but a major rebuild could take 18–24 months (or longer) due to planning, tendering, and contractor availability.

How to avoid it:

• Stress-test your timeline: claims handling + design + approvals + rebuild.

• Consider 24 or 36 months for more complex buildings.

• Make sure the loss of rent figure matches realistic occupancy and rent levels.

8) Contents and IT values quietly grow over time

How it happens: Office businesses add laptops, monitors, servers, AV equipment, and furniture over years. The contents sum insured stays the same.

How to avoid it:

• Do an annual contents inventory.

• Include leased equipment where you’re responsible for replacement.

• Check sub-limits for portable equipment and items away from the premises.

9) Misunderstanding “day one” / declared value policies

How it happens: Some commercial property policies use a “declared value” or “day one” basis to reduce underinsurance risk, but it still relies on accurate declared values and correct inflation provision.

How to avoid it:

• Ask your broker whether a day one basis is suitable.

• Confirm what percentage uplift is applied and whether it’s adequate.

• Still review declared values regularly.

10) Relying on old valuations or desktop estimates

How it happens: A reinstatement figure from 8–10 years ago is reused, sometimes copied from one renewal to the next.

How to avoid it:

• Treat RCAs as time-sensitive.

• Refresh every 3–5 years (or sooner after major changes).

• Keep documentation so decision-makers can see when and how values were set.

How the “average clause” can reduce your claim

Many commercial property policies include an underinsurance clause (often called average). Here’s a simple example:

• True reinstatement cost: £2,000,000

• Buildings sum insured: £1,500,000 (25% underinsured)

• Claim amount: £200,000

If average applies, the insurer may pay only 75% of the claim:

• £200,000 × (1,500,000 ÷ 2,000,000) = £150,000

You’d need to fund the £50,000 shortfall (plus any excess). This is why underinsurance can hurt even on partial losses.

Practical checklist: how to avoid underinsurance in office buildings

Use this as a renewal and mid-year review checklist.

Buildings (landlord or owner-occupier)

• Commission a reinstatement cost assessment from a qualified surveyor.

• Confirm the figure includes:

  • Demolition and debris removal

  • Professional fees

  • External works (car parks, boundary walls, signage)

  • Specialist plant and systems (HVAC, lifts, fire systems)

• Review after refurbishments, extensions, or major upgrades.

• Check index-linking and whether it reflects construction inflation.

Contents (tenant or owner-occupier)

• Update contents sums insured annually.

• Confirm cover for:

  • IT equipment (including portable items)

  • Items away from the premises

  • Fixtures and fittings you’re responsible for

• Check single item limits and sub-limits.

Business interruption / loss of rent

• Choose an indemnity period that matches realistic rebuild timelines.

• Ensure gross profit or rent figures are up to date.

• Consider increased cost of working to keep operations running.

Governance and documentation

• Assign an owner: landlord, managing agent, finance director, or facilities lead.

• Keep a record of:

  • Valuation date and methodology

  • Major works and costs

  • Annual review notes

• Don’t rely on “last year’s numbers” without checking.

Warning signs you might be underinsured

• Your buildings sum insured hasn’t changed in 3+ years.

• You’ve refurbished, reconfigured, or upgraded services since the last review.

• Your building has specialist systems (lifts, air handling, comms rooms) but the sum insured seems “low.”

• Your BI/loss of rent indemnity period is 12 months by default.

• You’re using market value, purchase price, or a mortgage valuation.

FAQs: underinsurance in office buildings

What’s the difference between market value and reinstatement value?

Market value is what the building could sell for. Reinstatement value is the cost to rebuild it after a total loss, including fees and clearance.

Does index-linking guarantee I’m not underinsured?

No. Index-linking helps, but it may not keep pace with construction inflation or reflect major changes like refurbishments.

How often should I get a reinstatement cost assessment?

Typically every 3–5 years, and after major works. High-spec or complex buildings may benefit from more frequent reviews.

Can tenants be underinsured too?

Yes. Tenants can be underinsured on contents, tenant improvements, and business interruption. It’s common when office equipment grows over time.

What is the “average clause”?

It’s a policy condition that can reduce claim payments if the sum insured is too low compared to the true value at risk.

Does underinsurance affect small claims?

It can. If average applies, even a partial loss claim may be reduced proportionally.

Are landlord and tenant policies ever overlapping?

They can be. That’s why it’s important to clarify who insures what under the lease and avoid gaps or duplication.

Can a broker help prevent underinsurance?

A good broker will ask the right questions at renewal, recommend RCAs where needed, and help you structure buildings, contents, and BI cover correctly.

Conclusion

Underinsurance in office buildings usually isn’t deliberate — it’s the result of outdated valuations, changing fit-outs, inflation, and unclear responsibilities between landlords and tenants. The fix is straightforward: base your sums insured on proper reinstatement assessments, review values regularly, update cover after works, and make sure business interruption and loss of rent reflect real-world rebuild timelines.

If you want a quick sense-check of your current sums insured and policy structure, speak to a specialist commercial broker who can help you reduce the risk of claim shortfalls and keep your cover aligned with your building’s true exposure.