To calculate your buildings sum insured, you need the full reinstatement cost of your property: the total expense of demolishing what remains after a loss, clearing the site, and rebuilding from the ground up to current building regulations. That figure has nothing to do with market value, purchase price, or what your mortgage lender estimated.
For a standard estate-type home, the Society of Chartered Surveyors Ireland provides a rebuild calculator that gives you a reliable minimum base figure in minutes.
For commercial property, apartments, period buildings, and high-value homes, that calculator doesn’t apply. Using it anyway is how the most serious underinsurance problems in Ireland start.
What Is a Buildings Sum Insured?
Your buildings sum insured is the maximum amount your insurer will pay to reinstate your property following a total loss. It’s based on the full reinstatement cost: the total expense of demolishing what remains, clearing the site, and rebuilding the structure from the ground up, in compliance with current building regulations, to the same standard as before.
Market value is a different figure entirely. It includes the land, the location, and whatever demand exists for property in your area at a given time. The rebuild cost covers only the physical structure and everything required to reinstate it. In Dublin and other major urban centres, the rebuild cost is now often higher than the open market price.
In rural areas, the reverse tends to be true. Basing your sum insured on a sale price or a mortgage valuation is one of the most common causes of underinsurance I encounter in my work.
How Does the SCSI Rebuild Calculator Work?
For standard estate-type homes built in Ireland since the 1960s, the Society of Chartered Surveyors Ireland (SCSI) publishes annual rebuilding rates by region. These form the basis of the SCSI rebuild calculator, the tool most homeowners and brokers use as a starting point.
The process is straightforward. You calculate the gross internal floor area of your property by measuring the internal dimensions at each floor level and adding the figures together. You then enter that total floor area into the SCSI rebuild calculator, select the correct house type and region, and account for any additional costs: a separate garage, higher-than-average kitchen fittings, built-in wardrobes, or outbuildings such as sheds.
The figures produced are minimum base costs. They include demolition costs, professional fees, and VAT at 13.5% on building works and 23% on professional fees. For a full breakdown of regional residential rebuild rates across Ireland, including the most recent SCSI figures, see my earlier guide on rebuild costs.
It’s a useful tool. For the right property type, used correctly, it gives you a reliable floor figure to work from.
The problem is that most of the properties carrying the most significant underinsurance risk are the ones this calculator was never designed to assess.
Which Properties the SCSI Calculator Does Not Cover?
The SCSI state this clearly on their own calculator page. The rebuild calculator covers estate-type homes only. It doesn’t apply to the following property types.
Commercial buildings. Offices, retail units, warehouses, industrial premises, and mixed-use developments sit entirely outside the scope of the SCSI residential calculator. Commercial rebuild costs are driven by mechanical and electrical services, specialist finishes, commercial-grade cladding, fire suppression systems, and floor loadings designed for business occupancy.
None of these factors appear in a residential calculation. A commercial property owner who uses residential rates is almost certainly underinsured from the moment the policy is written.
Apartments and multi-unit developments. Block insurance requires a whole-building reinstatement assessment: common areas, structural elements, lifts, communal services, and shared infrastructure all need to be included. A residential calculator built around individual houses can’t produce that figure.
Period and protected structures. This is where the gap between calculator estimate and actual cost tends to be largest. Victorian and Georgian properties, listed buildings, and other protected structures require specialist materials and craftsmanship that have no equivalent in standard modern construction. Recreating period joinery, lime mortar stonework, or ornamental features means sourcing skilled tradespeople at a premium an average rate per square metre won’t capture.
One-off rural and bespoke homes. Architect-designed properties, self-builds with non-standard construction methods, and thatched properties all carry rebuild costs that deviate significantly from estate-type norms. So do homes with restricted site access, which adds to demolition and construction costs in ways the calculator doesn’t account for.
Properties with more than three storeys or with basements. The SCSI calculator provides no rates for these configurations. Full stop.
High-net-worth homes. Premium finishes, extensive smart systems, large outbuildings, and significant landscaping all push the reinstatement cost well above any standard regional rate. A valuation needs to account for what is actually there, not what a typical estate home contains.
If your property falls into any of these categories, the SCSI calculator will not give you a reliable sum insured figure. Using it anyway does not protect you. It produces a number that carries the appearance of credibility while leaving you materially underinsured.
What a Commercial Sum Insured Must Include
For commercial property owners and managing agents, calculating the correct sum insured involves a level of detail that goes well beyond a residential assessment. The consequences of getting it wrong are proportionally larger. A commercial claim following a fire or major flood can run into millions. The average clause applied at that scale produces a shortfall measured in hundreds of thousands of euros.
A correct commercial sum insured needs to account for the following.
Structural reinstatement. The full cost to rebuild the structural shell: foundations, frame, floors, walls, roof, and facade, using materials that meet current building regulations and replicate the original specification.
Demolition and site clearance. Before any rebuild begins, the damaged structure must come down and the site must be cleared. For commercial buildings, this can involve specialist demolition contractors, asbestos surveys and removal for older buildings, and disposal costs for commercial quantities of debris.
Mechanical and electrical services. Commercial properties contain HVAC systems, commercial electrical switchgear, fire detection and suppression systems, data cabling infrastructure, lift installations, and in some cases specialist process equipment. These must be explicitly included in the assessment.
Professional fees. A commercial reinstatement requires a team of professionals. Fees for a chartered building surveyor or architect, a structural engineer, a chartered quantity surveyor, and building control compliance certification are all part of the total. These fees typically add 12 to 15 percent to the core build cost and are one of the most common areas of underinsurance when property owners estimate their own figures without professional input.
VAT at the correct rates. VAT at 13.5% applies to building works. VAT at 23% applies to professional fees. Both must be included in the total reinstatement figure.
The declared value and the sum insured. The distinction matters and it catches people out. The declared value is the full reinstatement cost produced by a professional assessment. The sum insured is the declared value plus an inflation provision, typically between 20 and 50 percent on top, to account for construction cost movement over the policy period. Get the declared value wrong at the outset and the sum insured will be wrong too, regardless of whatever inflation uplift the insurer applies to it.
What Is a RICS Reinstatement Cost Assessment?
For commercial buildings, period properties, and high-value homes, the correct replacement for the SCSI calculator is a RICS Reinstatement Cost Assessment. Conducted by a RICS-regulated chartered building surveyor, it produces a declared value based on a physical inspection of the property, a detailed elemental analysis of all construction components, and the application of current construction cost data.
The process begins with an on-site survey. The surveyor inspects the property in full, records the construction specification, takes measurements, notes any specialist elements, and documents the features that affect reinstatement cost. That on-site data then feeds into an elemental cost analysis, working through the building component by component from substructure to external works, applying current tender price indices and relevant location factors.
The report delivers a declared value that a RICS-regulated professional is prepared to stand behind.
That matters when a claim is made. Loss adjusters appointed by insurers to assess major commercial claims will verify the sum insured figure as part of their investigation. A declared value from a professional RICS RCA is one they can work with. A figure from a residential calculator, a historical valuation, or an unverified estimate is one they can challenge. And frequently do.
I’ve spent 20 years working across building surveying and insurance claims in Ireland. The cases where underinsurance causes the most damage are rarely the ones where the property owner knew nothing about reinstatement costs.They’re the ones where a figure that felt reasonable, often a number carried forward from a valuation done four or five years earlier, was never professionally verified before the claim came in.
I’ve seen commercial properties in Dublin where the declared value hadn’t been updated since 2019. By the time the loss adjuster ran the numbers, the gap was substantial. That gap closes before a claim, not after.
For period homes, high-value residential properties, and architect-designed homes that fall outside the SCSI calculator’s scope, an on-site RCA serves the same function. It replaces an estimate with a professionally calculated figure.
How Often Should Your Sum Insured Be Reviewed?
National average rebuild costs rose by approximately 21% in 2022, around 12% in 2023, 6.2% in 2024, and a further 7% in 2025, according to the SCSI’s annual House Rebuilding Guide. Even at the more moderate rates seen in recent years, a commercial property whose declared value has not been reviewed in three years may already be materially underinsured. On a property with a declared value of €1 million, a 7% annual construction cost increase over three years adds approximately €225,000 to the true reinstatement figure. That gap does not appear on the policy. It appears at the claim.
In my experience, a full on-site RCA every three to five years is the appropriate interval for most commercial properties, with annual index-linked adjustments applied between reviews. Most commercial policy wordings align with this frequency.
At Rebuild Valuation, we also offer desktop rebuild cost reviews at the two to three year point between on-site assessments. These allow the declared value to be updated without the full cost and time of a new site inspection. Desktop reviews aren’t RICS-regulated assessments. They’re a cost-effective interim measure, appropriate between formal on-site reviews, not a replacement for them.
If you have made significant changes to your property, an extension, a fit-out upgrade, new M and E systems, or any structural alteration, the sum insured should be reviewed immediately rather than waiting for the next scheduled renewal.
What Happens If Your Sum Insured Is Too Low?
The average clause is the mechanism insurers use to reduce claim settlements when a property is underinsured. Its application is straightforward. Brutal, but straightforward.
If your building is insured for 70% of its true reinstatement cost, your insurer will pay 70% of any valid claim. Regardless of the size of the loss.
Here’s what that means in practice. You own a commercial unit insured for €800,000. A fire causes €250,000 of damage. The loss adjuster’s inspection during the claim determines the correct reinstatement cost is €1,100,000, meaning you were insured for approximately 73% of the true value. Under the average clause, your insurer pays 73% of the €250,000 claim, which is €182,500. You cover the remaining €67,500 yourself, out of resources you wouldn’t have expected to need.
The same proportional reduction applies whether the claim is for partial loss or total loss. The insured party has no recourse. The clause is standard, its application is lawful, and the shortfall is the policyholder’s responsibility.
The difference between an estimated sum insured and a professionally calculated one on a large commercial property can run well into six figures. That gap can’t be recovered after a claim. It can only be addressed before one.
What Brokers Should Know About Commercial Reinstatement Figures
If you place commercial property insurance for clients, the accuracy of the declared value on their policy matters as much to you as it does to them.
When a major claim arises and a loss adjuster determines the property was underinsured, the shortfall falls on your client. But the questions that follow often extend to the professional advice they received: what they were told about getting the sum insured right, and whether a formal assessment was recommended at any point.
A broker who has consistently flagged outdated reinstatement figures and recommended professional assessments for commercial risks is in a defensible position. A broker who has accepted client-supplied figures without question is not. The phone call that follows a major underinsured claim is not a conversation any broker wants to have twice.
We work with insurance brokers across Ireland to provide RICS-compliant Reinstatement Cost Assessments for commercial property clients. If you manage a book with commercial property risks and want to discuss a working relationship, view our on-site assessment service.
Your Buildings Sum Insured Questions Answered
How do I calculate my buildings sum insured for a commercial property?
You can’t do it reliably with an online tool or a residential rebuild calculator. The correct approach is a RICS Reinstatement Cost Assessment: a physical inspection by a RICS-regulated chartered building surveyor, followed by a full elemental cost analysis of the building. That process produces a declared value you can actually rely on.
What should the sum insured value be for a building?
The full reinstatement cost. That means demolition and site clearance, structural rebuild, mechanical and electrical services, professional fees, VAT at the correct rates, and an inflation provision for the policy period. It should never be based on market value or purchase price.
What happens if my sum insured is too low?
Your insurer applies the average clause and reduces your settlement by the same proportion you’re underinsured. Sixty percent of the true reinstatement cost means sixty percent of any claim, whether it’s a total loss or a burst pipe. The shortfall is yours to cover.
Do I need a chartered surveyor to calculate my sum insured?
For a standard estate-type home, the SCSI rebuild calculator gives you a reliable minimum base figure. For any other property type, including commercial buildings, period homes, apartments, non-standard construction, and high-value residential properties, yes. Using a residential calculator for these property types isn’t a conservative estimate. It’s an unreliable one.
How often should I update my buildings sum insured?
Every three to five years for a full on-site RCA, with annual index-linked adjustments in between. Any significant change to the property, an extension, a fit-out upgrade, new M and E systems, should trigger a review immediately rather than waiting for the next scheduled assessment.
What is the difference between declared value and sum insured?
The declared value is what a surveyor calculates the property would cost to reinstate today. The sum insured is that figure plus an inflation provision added by the insurer, typically between 20 and 50 percent, to cover construction cost movement during the policy period. Both need to be right. An error in the declared value flows through to the sum insured and you won’t know about it until a claim.
Get a Professional Reinstatement Cost Assessment in Ireland
If your property is commercial, non-standard, or high in value, a professional assessment is the correct starting point. Not an estimate, not a calculator, and not a figure carried forward from a valuation several years ago.
As a RICS Chartered Building Surveyor with over 20 years working across building surveying and insurance claims in Ireland, I provide on-site Reinstatement Cost Assessments that produce a declared value insurers and loss adjusters can work with. The assessment gives your broker what they need to place the risk correctly. It means that if a claim arises, the process starts from solid ground rather than a disputed number. Relative to the financial exposure of a six-figure underinsurance shortfall, a professional RCA is one of the lower-cost risk management decisions a commercial property owner can make.
If you’d like to know the correct declared value for your property, the next step is a short conversation. We’ll discuss the property type, confirm whether an on-site RCA is the right approach, and give you a clear picture of what the assessment involves before you commit to anything.
Most people find it takes less than fifteen minutes to establish whether a full assessment is needed and what that looks like. Use the contact form on our website or call the office directly.
Trevor Kelly is a RICS Chartered Building Surveyor and Managing Director of Rebuild Valuation (trading name of Trevor Kelly Insurance Claim Solutions Ltd), RICS Regulated Firm No. 860896. He is a member of the Society of Chartered Surveyors Ireland, the Insurance Institute of Ireland, and the British Damage Management Association.