Buying a house with an illegal extension on Mallorca: Legalise, price reduction or accept?

You've found the perfect finca between Llucmajor and Algaida – or your parents left you the stone house with the conservatory that your grandfather already added on. And then the disillusionment: the extension isn't in the municipality's building plan, the town hall calls it "illegal". This is no isolated case on Mallorca – according to a study by the Col·legi Oficial d'Enginyers Tècnics en Topografia (CQNE), around a third of the island's rural buildings are illegal or only partially legalised. This guide shows you when such a house can be legalised, how much of a price reduction is realistic when buying, when you can simply accept the risk – and what you need to do if you inherit rather than buy a house with unclear building status.

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Why illegal extensions are so widespread on Mallorca

The cause is rarely malicious intent. Between the 1990s and the early 2010s, extensions on Mallorca were often carried out "quietly", without municipalities systematically checking. Conservatories, terrace roofs, garages or a shed converted into a guest house – all of this usually had no legal consequences. It was only with the founding of the Agència de Defensa del Territori (ADT), an authority subordinate to the Consell de Mallorca, that this changed: instead of warnings, the ADT now issues real fines and demolition orders.

Note: In the Balearics there are an estimated 30,000 buildings on rural land (suelo rústico) that were not built legally or not fully legally – for many of these, the authorities can no longer prosecute the original violations due to the statute of limitations, but that doesn't automatically make them legal.

Buying or inheriting: three paths at a glance

Whether you buy or inherit – in the end, you basically have three options open to you. Which one suits you depends on the age of the extension, its location (building land or protected zone), and whether a legalisation window is even still open.

Route 1 – Cure it: The legalisation procedure

Since the Decree-Law of 24 May 2024, there has for the first time been a structured procedure in the Balearic Islands to legalise such legacy issues within a three-year period under certain conditions. The decree is intended to create legal certainty for owners, provide additional revenue for municipalities, and at the same time improve environmental and energy standards.

1. Check the urban planning status at the relevant town hall (building permits, possible AFO – "Asimilado a Fuera de Ordenación")
2. Check whether the property is located in a protected zone (suelo rústico protegido) – legalisation is usually excluded there
3. Have a technical project drawn up by an architect/aparejador
4. Submit the application for legalisation together with payment of the fine
5. After approval: registration of the change in the Cadastre and the Land Registry

Please note: Not every unauthorised building can be legalised. If the extension is located in a protected zone such as the Tramuntana, or was built after the respective municipal deadlines had expired, demolition is often the only option – as in the case of a couple near Llucmajor, whose conservatory, registered in the Land Registry but never applied for at the town hall, could not, according to the municipality, be legalised retroactively, even upon payment of taxes and fines.

Grandfathering vs legality: the crucial difference

Many buyers and heirs confuse "grandfathering" with "legality" – an expensive mistake. A building is only legal if it was constructed in accordance with the regulations of the respective municipality in force at the time of construction (boundary distances, height, built-up area, type of use), with a building application, permit, and final inspection. Grandfathering, on the other hand, only means that the authority can no longer sanction an original violation because the deadline has expired – the building nevertheless remains "not legal" under building law, with restrictions on conversion, expansion, and sometimes on sale.

Route 2 – Negotiating a price reduction: realistic ranges

If the extension can in principle be legalised, a price reduction is often the most pragmatic approach. What is typically negotiable are the expected costs for the legalisation project, the fine, and fees – plus a risk premium in case the municipality proves difficult. Important: before making a reservation, get a written assessment from a local architect or lawyer before agreeing on a specific reduction.

Note: Without a clear legal status, you should not sign a reservation contract. Clarify the urban planning status beforehand – you'll find details on the safe process in the guide to the reservation contract.

Route 3 – Accepting: When the risk is bearable

Accepting doesn't mean looking away, but consciously living with the limitations. This can make sense if the extension is old enough that the authority can no longer pursue the original violation (grandfathered protection/Bestandsschutz), you're not planning any extension or change of use, and you don't intend to resell the property in the short term. Professional estate agents nowadays often no longer take illegal houses into their portfolio unless at least grandfathered protection has been proven – you should apply the same standard.

Warning: In 2019 alone, the ADT issued dozens of demolition orders, with several hundred further proceedings ongoing. "No longer an isolated case", as a legal expert from a Palma law firm emphasises – anyone relying purely on sitting it out should not underestimate the authority's current enforcement course.

Special case inheritance: Illegal extension in the estate

If you inherit a property with an illegal extension, you automatically also take on the building-law liabilities – legally, there's no "no thank you" without renouncing the entire inheritance. The assessment basis for Spanish inheritance tax is the market value of the property at the time of death; for non-residents, the tax authorities scrutinise this value particularly closely. Before deciding on acceptance, legalisation or sale, you should bring in German and Spanish advisors in parallel, as inheritance tax and building-law status influence each other – an unclear extension usually lowers the market value relevant for tax purposes, but can also trigger disputes in disagreements with the tax office.

1. Check the certificate of inheritance (Erbschein) or grant of probate and the land registry status in parallel
2. Enquire about the urban planning status of the entire building at the town hall
3. Clarify with a tax advisor how the extension affects the assessment basis
4. Make a decision: legalise, sell at a reduced price, or hold as a grandfathered-protection property
5. If intending to sell: inform the buyer transparently about the status

Note: You'll find more on deadlines and tax rates for property transfers in the guide Inheritance & Gifting Balearics.

Due diligence before the purchase: these are the documents you need

Before signing anything, you should review the following documents – ideally with the support of an independent lawyer who is not instructed by the seller.

Note: Even the best notary in Spain does not automatically check whether all extensions are approved – unlike in Germany, this verification is your responsibility or that of your lawyer.

Taxes and additional costs for encumbered properties

The building status does not change the basic tax burden on purchase. For resale properties, the Balearic property transfer tax (ITP) applies progressively – regardless of whether an extension is legal or not. So factor in the price reduction for the illegal extension in addition to the regular purchase-related cost calculation.

As a rough rule of thumb, you should budget 12–14 % of the purchase price for taxes, notary and additional costs when buying a resale property – for a property with an illegal extension, the costs of legalisation or the negotiated price reduction come on top. Details on all additional costs can be found in the guide Purchase-related costs Mallorca and on the current ITP scale in the guide ITP Balearic Islands 2026.

Most Common Mistakes

• Signing the reservation contract before checking the urban planning status with the town hall
• Confusing legal protection status (bestandsschutz) with full legality
• Negotiating a price reduction without first obtaining a technical report on the real legalisation costs
• Accepting an inherited property without first checking its building status
• Relying on the seller's verbal assurances of "upcoming legalisation" instead of demanding written evidence
• Overlooking outstanding IBI payments on the extension and becoming liable for them after the notary appointment

What Happens Next?

Whether you've opted to legalise, negotiate a price reduction, or accept the situation, the work doesn't end on notary day. After the purchase or acceptance of the inheritance, you should document the chosen status: for legalisation, initiate registration with the Cadastre and Land Registry; for accepted legal protection status, avoid any further structural changes without a fresh review; and if you plan to rent the property out, keep an eye on the Cédula and Energy Performance Certificate status, as both documents are required for legal rental. Anyone planning to sell the property later should proactively disclose the building-law status to future buyers – this avoids disputes and considerably speeds up the sales process.

Checklist: Illegal Extension in 8 Steps

1. Request a Land Registry extract (Nota Simple), no older than 30 days
2. Check the urban planning status directly with the relevant town hall
3. Check whether the property is located in a protected zone (suelo rústico protegido, Tramuntana)
4. Commission an independent architect/lawyer for an initial technical assessment
5. Determine: Is the extension legalisable, protected by legal status, or at risk of demolition?
6. Obtain a cost estimate for legalisation (project, fines, fees)
7. Negotiate a price reduction or withdraw the purchase intention based on these figures
8. Record the outcome in writing in the reservation or purchase contract

Conclusion

Buying or inheriting a house with an illegal extension on Mallorca is not a dealbreaker – but it does call for sober assessment rather than gut feeling. Around a third of the island's rural development is affected by this issue, and the ADT is pursuing violations more rigorously today than just a few years ago. Anyone who clarifies the urban planning status before signing, weighs up legalisation, a price reduction, and consciously accepting the legal protection status, and realistically factors in all costs, can safely acquire a property with a building-law history – or make a confident decision in the case of inheritance.

Official Sources

• Col·legi Oficial d'Enginyers Tècnics en Topografia (CQNE): https://cqne.cat/
• Agència de Defensa del Territori (ADT) – Consell de Mallorca (the authority responsible for building violations on Mallorca)
• Decree-Law on the legalisation of older buildings on rural land, Balearic Islands, dated 24 May 2024