If you are buying a villa on the Costa Cálida — around Mazarrón, Puerto de Mazarrón, Águilas, Los Alcázares or the inland huertas of Murcia — there is a very good chance the property does not match its own paperwork. A glazed terrace, a covered porch, an enlarged pool deck or a rooftop solarium has often been added years after the villa was built, without being declared. In most cases this can be legalised, but the route and the cost depend on when the work was done and where the villa sits. This article explains, in plain terms, how to tell whether an extension is a problem and how to fix it before you sign.
The short version: an undeclared extension is a "discrepancy" between what physically exists and what is recorded in the escritura (title deed), the Land Registry and the catastro (cadastre). If the extension is old enough and does not sit on protected land, it can usually be regularised with an obra nueva por antigüedad (declaration of old works based on prescription), signed at the notary and updated at the registry and cadastre. If it is recent, unlicensed, or on the wrong type of land, you may need a retrospective licence — or you may not be able to legalise it at all. Never complete on a villa without knowing which situation you are in.
An undeclared extension is any built element that changes the buildable footprint or living area of the villa but was never registered. On Costa Cálida and Costa Almería villas the usual culprits are:
The key test is not whether it looks nice — it is whether the built surface area on the ground and the number of usable rooms match the figures in the title deed and the cadastral record.
Spain records property in two parallel systems. The escritura and its Land Registry entry establish ownership and legal rights. The catastro is a tax and mapping database run by the Ministry of Finance that records the physical description — surface area, layout and the "valor de referencia" used as the tax base. The two are meant to align, but historically they drift apart, especially on older resale villas where owners built terraces and solariums quietly over the decades.
When you order the nota simple you get the registry's version; your lawyer should then cross-check it against the current cadastral certificate and, ideally, a physical measurement of the property. A gap between them is an escritura vs catastro discrepancy. It does not automatically make the property illegal, but it must be resolved so that what you buy on paper is what you actually take possession of.
Bear in mind that the cadastral valor de referencia also sets your purchase-tax floor. In Murcia (Costa Cálida) resale ITP is 7.75% in 2026 (the widely-quoted 8% figure is out of date after Ley 3/2025), calculated on the higher of the price or the valor de referencia. If an extension is later added to the cadastre, the reference value — and therefore your future IBI and tax base — can rise. That is one reason sellers sometimes leave works undeclared.
Spanish planning law gives town halls a limited window to act against unlicensed building works. Once that window closes, the authority can no longer order demolition or impose the original planning fine — the infringement has prescribed. This is the legal basis for the obra nueva por antigüedad: a notarial declaration that a structure has existed, undisturbed and unchallenged, for longer than the enforcement period.
In the Region of Murcia the general enforcement period for works on ordinary urban or developable land is four years from completion. Once that has passed and provided the works are not on specially protected land, you can declare them as old works and register them. Crucially, prescription bars enforcement — it does not grant a licence retrospectively and it never runs at all on protected soil (coastal Ley de Costas zones, green belt, special rural protection). On such land, unlicensed works can be pursued indefinitely and cannot be legalised by the passage of time.
There are two broad routes, and which one applies depends entirely on the age and location of the works.
| Route | When it applies | What's needed | Typical cost |
|---|---|---|---|
| Obra nueva por antigüedad (old-works declaration) | Works older than the enforcement period (≈4 years in Murcia), on non-protected land | Architect's certificate dating the works + cadastral/aerial proof; notary deed; registry + cadastre update | Architect ~€400–900; notary ~0.2–0.5%; registry ~0.1–0.25%; gestoría ~€300 |
| Retrospective licence (legalización) | Recent works, or where the town hall still has enforcement power and the build complies with current rules | Full project by architect, town-hall application, possible planning fine, technical approval | Architect fees + licence tax (ICIO ~2–4% of works value) + any fine; €1,500–6,000+ |
| Not legalisable | Works on protected/rústico-protegido land, coastal setback zone, or exceeding buildable limits with live enforcement | May require demolition; walk away or renegotiate | n/a — a red flag |
The obra nueva por antigüedad is the common, affordable path for the typical enclosed terrace or 15-year-old solarium. A registered architect (arquitecto) issues a certificate stating the surface area and estimated age of the structure, usually backed by historical aerial photography from the catastro or PNOA image archives. Your lawyer and notary then execute a new obra nueva declaration, which is inscribed at the Land Registry and pushed through to the cadastre so all three records finally agree.
Legalising the works on paper does not always give you a valid cédula de habitabilidad for the extra habitable area, nor a first occupation licence covering it. If the extension added a bedroom or an enclosed living space, check whether that space is recognised for habitability and utility-supply purposes — otherwise you may struggle to set up or upgrade utilities or to obtain a tourist rental licence that counts the extra beds.
Many Costa Cálida and Costa Almería villas sit on rústico (rural) land. Here the picture is different again. Andalucía uses the AFO certificate (Asimilado a Fuera de Ordenación) to recognise unlicensed rural builds that can no longer be enforced against; Murcia has broadly comparable "out of ordinance" mechanisms. In both cases the house is tolerated rather than fully legal, and extensions on protected rural soil generally cannot be regularised at all. If the villa relies on a borehole rather than mains supply, read our guide to rural water connections as well, because an undeclared extension often coincides with informal services.
This is negotiable and should be pinned down before the reservation deposit. Three common outcomes:
Whatever you agree, do not let a mortgage complicate it. Lenders and their valuers care about legality: an undeclared area may be excluded from the bank valuation (tasación), reducing how much you can borrow, and some banks will not lend at all until the registry description is corrected. If you are financing the purchase, factor this into your non-resident mortgage planning early.
None of this should scare you off a great Costa Cálida villa. Undeclared terraces and solariums are extremely common and usually resolvable for a few hundred to a couple of thousand euros. What matters is discovering the discrepancy before you sign the escritura, not after.
Not necessarily. An undeclared extension is a discrepancy between the physical property and its records. If the works are old enough that the town hall's enforcement window has passed (around four years on ordinary land in Murcia) and they are not on protected soil, they can usually be legalised through an obra nueva por antigüedad. Recent or protected-land works are more serious.
It is a notarial declaration that a building or extension has existed unchallenged for longer than the planning enforcement period, backed by an architect's certificate and aerial evidence of its age. Once signed, it is inscribed at the Land Registry and updated in the cadastre, bringing the escritura and catastro into line.
For an old-works declaration, expect roughly €400–900 for the architect's certificate plus notary (~0.2–0.5%), registry (~0.1–0.25%) and gestoría (~€300) costs. A retrospective licence for recent works costs more because of the full project, the ICIO construction tax (~2–4% of works value) and any planning fine.
Sometimes. On ordinary rural land older works may be recognised via mechanisms similar to Andalucía's AFO certificate. On specially protected rural soil or within the coastal Ley de Costas setback, prescription does not run and the works generally cannot be legalised at all — a serious red flag.
Yes. Bank valuers may exclude the undeclared area, reducing your loan amount, and some lenders will not release funds until the registry description is corrected. Resolve discrepancies early if you are borrowing.
It can. Updating the cadastre with extra surface area raises the valor de referencia, which feeds into your annual IBI and can affect the tax base for future transactions. It is still far cheaper than the risk of an unresolvable discrepancy when you come to sell.
Every villa on the Costa Cálida, Costa Blanca, Costa del Sol and Costa Almería is different, and paperwork discrepancies are exactly the kind of detail that separates a smooth purchase from a stressful one. Our team checks the escritura against the catastro on every property we sell and works with trusted lawyers and architects to get extensions legalised the right way. Contact Mediter Real Estate today to find a villa with clean papers — or to check the one you have fallen in love with before you sign.
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