Why the Square Metres in a Property Listing May Be Wrong

Area is the number buyers anchor on. It drives price per square metre, mortgage valuation, tax records and the comparison you make between two properties on the same street. It is also the number most likely to differ depending on who produced it.

This is not primarily a story about deception. It is a story about definitions. Different sources measure different things, at different times, for different purposes — and then all of them get shortened to "m²" in conversation.

One property, several legitimate area figures

Here are the figures you are likely to encounter, and what each one usually represents.

• Estate-agent advertised area — a marketing figure, often the most generous interpretation available, sometimes including terraces, porches, basements or a garage.
• Seller-reported area — what the owner believes, frequently remembered from their own purchase or from work carried out since.
• Registry area — the description held in the land registry, which may date from the original declaration and may not reflect later work.
• Cadastral area — the tax-administration record, maintained for fiscal purposes and updated on its own schedule.
• Architect measurement — a current physical measurement, produced under a stated methodology for a stated purpose.
• Internal usable area — the space inside the walls that you can actually furnish and walk on.
• Gross constructed area — usable area plus internal and shared wall thickness, and often structural elements.
• Terraces, porches and covered outdoor space — sometimes counted in full, sometimes at 50%, sometimes not at all.
• Basement and lower-ground space — often excluded from habitable area even where it is used daily.
• Garage, storage and ancillary buildings — commonly recorded separately, and easily double-counted in a listing.

A worked example

Take a fictional villa. The listing advertises 238 m². The cadastral record shows 209 m². An architect measuring the building today arrives at approximately 261 m². The seller describes the house as "about 250".

Read together, these four figures tell a coherent story: the property has probably been extended or enclosed since it was originally recorded, and the records have not caught up. That is a very different conclusion from any single number, and it points to a specific next question — where is the licence for the additional 52 m²?

So what exactly are you paying for?

This is the question that turns an area discrepancy from trivia into money. When you calculate €/m², which area are you dividing by? If the asking price is €995,500 and you use 261 m², you get roughly €3,814/m². Use 209 m² and the same price becomes €4,763/m² — a 25% difference in the metric you are using to judge value.

Neither calculation is wrong. But if you compared this property against a neighbour's listing that quoted only recorded area, you would be comparing two different things and drawing a confident conclusion from it.

Where area discrepancies have real consequences

Mortgage valuation

A valuer working for a bank generally values what is legally recorded and verifiable, not what is physically present. If 52 m² of a house is not documented, a valuation can come in lower than the price, and the shortfall lands on your deposit.

Resale

Whatever you accept today, your future buyer's lawyer will raise tomorrow. A discrepancy you absorbed at purchase becomes a negotiating point against you at sale — often with less flexibility, because by then it is your paperwork.

Planning and renovation permissions

Extension rights are frequently expressed as a ratio of plot to permitted built area. If the recorded built area is understated, you may believe you have headroom to extend that you do not have — or, occasionally, the reverse.

Tax and running costs

Local property taxes are commonly calculated from cadastral values. Bringing records into line with reality can increase the assessed value and therefore the annual bill. That is not a reason to avoid regularisation, but it should be in your cost model.

Negotiation

Handled well, an area discrepancy is one of the strongest evidence-based negotiating positions available to a buyer, because it is documentary rather than subjective. It is difficult to argue with two records that disagree.

Why the numbers drift in the first place

Records drift for ordinary reasons. A terrace is glazed in and becomes a room. A garage becomes a studio. A basement is dug out and finished. Each change is real, each may even have been done competently, and none of them updates the registry automatically.

There is also honest methodological variation. Some measurements include half the thickness of party walls; some exclude them. Some count covered terraces at 50%. Some include the pool plant room; some do not. Two professionals can measure the same building carefully and produce different totals — which is why the methodology matters as much as the number.

What good looks like

A well-documented property has a registry description, a cadastral record and a physical building that agree within a small margin, with licences on file for any work carried out since construction. That property is easier to mortgage, easier to insure, easier to extend and easier to sell.

A property whose figures disagree is not automatically a bad purchase. It is a property with an open question, and open questions have prices. Your job before offering is to convert the question into a number: cost of regularisation, likelihood of success, timescale, and the discount a future buyer will apply if it is never resolved.

BuyerWingman reads the listing, the registry and cadastral information, the floor plans and the seller's statements together, flags where the areas disagree, and shows which figure came from which source — so the discrepancy is visible before you offer, not after. See also the documents you should request before buying.