The same property can be advertised at 120 sqm, described in the tax register at 96 sqm and permitted at 140 sqm. None of these figures is necessarily wrong: they measure different things. Confusing them is one of the most common causes of disagreement between buyer, seller, lender and planning authority.
Net floor area
The floor area of the rooms, measured inside the walls, excluding walls, columns, ducts and common circulation. It is the area actually used, and the fairest basis for comparing similar properties.
Gross private area
Adds to the net area the internal walls and half of the walls shared with other units or common spaces, plus enclosed balconies and private annexes. It is normally the area stated in the unit's documentation and the basis for several tax calculations.
Gross dependent area
Covers covered spaces in exclusive use but ancillary in nature: garage, storage, covered terrace, accessible loft. It contributes to value, but not with the weight of habitable area.
Construction area
The sum of the areas of all floors, measured to the outside of the walls. This is the figure that matters for permitting, because planning ratios are applied to it. It is usually the largest of the four.
Where each figure appears
| Document | Area normally stated |
|---|---|
| Tax register (caderneta predial) | Gross private and dependent area |
| Land registry certificate | Composition and described areas |
| Permitted design | Construction area and room areas |
| Sales listing | Varies, often the most favourable |
| Valuation report | Measured areas and the source of each |
Practical consequences
- Comparing prices per square metre without knowing which area was used produces errors of 15 % to 25 %. That is enough to distort a purchase decision.
- Differences between documents and reality must be explained. An enclosed balcony, a converted loft or an annex built later change areas and may amount to a planning breach.
- Lending valuations measure and reconcile. Where the measured area does not match the documented one, the difference is recorded and can affect the loan.
What to do before signing
Obtain the tax register, the land registry certificate and, where it exists, the use permit, and reconcile the areas against each other. If they differ, establish the cause before contracting: it is almost always fixable, but rarely quick once the promissory contract is signed.
DINAMESTRIA measures, reconciles and documents areas in valuations and in inspection and due diligence work. If you have doubts about a property's areas, our Property Valuation unit can clarify them.