What Happens If You Buy a Greek Property With Illegal Construction

A surprising share of Greek homes carry some form of unauthorized construction, an enclosed balcony, an extra room, a basement that became living space, a pool that never appeared on the plans. For a foreign buyer who falls in love with a stone villa on an island or a renovated apartment in Athens, this is one of the most important things to check before signing, because Greek law treats undeclared illegal structures as a hard block on the sale. Here is what actually happens if you buy into one.

What counts as an unauthorized construction in Greece?

An unauthorized construction, often called afthereto, is any building or alteration that does not match the approved building permit and plans, ranging from a closed-in veranda to an entire unpermitted floor. Greek law under Law 4495/2017 sorts these violations into five categories by severity and by when they were built, with the framework primarily addressing structures put up between 1955 and 2011. The label covers far more than obvious illegal builds; small discrepancies between the legal plans and the physical property are extremely common in older Greek homes.

Can you even buy a Greek property that has illegal construction?

Not until it is legalized, because since 2011 Greek law blocks the sale, transfer, gift, or mortgage of any property that has undeclared illegal structures. The transaction physically cannot complete at the notary without the proper declaration, so an unlegalized violation freezes the property. This means that if a seller has not regularized the construction, you are not buying a problem you can fix later; you are unable to close at all until it is resolved.

What is the engineer's legality certificate?

Every property transfer in Greece now requires a legality certificate issued by a licensed engineer confirming that the property's physical state matches its legal plans, or that any deviations have been declared and regularized. Only architects and engineers registered with the Technical Chamber of Greece can inspect the property, complete the legalizing declaration, and issue this certificate. No notary will finalize a sale without it, which makes the engineer's inspection one of the most important due diligence steps in a Greek purchase.

What happens if you buy without checking, and the certificate later fails?

In practice you cannot close without the certificate, so the real danger is buying under pressure or trusting a seller's assurance and discovering during the process that the property has violations the seller never legalized. At that point the sale stalls, you may have already paid for surveys and legal fees, and the cost and time to regularize the structure can fall into dispute between you and the seller. The honest risk is not owning an illegal building unknowingly; it is wasted cost and a collapsed transaction when the violations surface late.

What is the 2028 deadline foreign buyers keep hearing about?

The confirmed deadline to legalize unauthorized constructions in the main categories is 31 March 2028, and properties that miss it face a complete block on sale, transfer, gift, and mortgage, with authorities also gaining the power to issue demolition orders. For a buyer, this changes the calculus on a property with known violations: the legalization needs to be completed within that window, ideally by the seller before closing, or the asset risks becoming legally frozen and far harder to ever resell. Treat the deadline as a reason to insist the seller legalizes before you buy, not after.

Who should pay to legalize, the buyer or the seller?

Because an unlegalized violation blocks the sale, legalization is normally the seller's responsibility to complete before transfer, since they cannot legally sell otherwise. In a negotiation, a buyer who discovers violations can require the seller to regularize at the seller's cost as a condition of the purchase, or negotiate a price reduction to cover the work and take it on knowingly. What you should never do is close on a verbal promise that it will be sorted out later, because the leverage disappears once the money has moved.

How much does legalization cost and how long does it take?

Costs depend on the category and size of the violation, because the engineer's fees and the regularization fines scale with severity, so a minor enclosed balcony is modest while an entire unpermitted floor is substantial. The process also takes time, as the engineer must survey the property, file the declaration, and process it through the system. Build this into the timeline and budget rather than assuming a quick fix, and get the engineer's cost estimate in writing before you commit.

Does this apply to island properties and new builds too?

It applies across Greece, and older island properties are especially likely to carry small undeclared additions accumulated over decades, which is exactly where many foreign buyers are shopping. Newer builds are not automatically safe either, since deviations from the permit can occur during construction. Greece has also tightened building rules in high-demand spots such as Mykonos and Santorini, so on the islands the rules around what can be built and legalized deserve particular attention.

How do you protect yourself before buying in Greece?

Engage your own independent engineer registered with the Technical Chamber of Greece to inspect the property and compare its physical state against the legal plans before you pay anything, and make a clean legality certificate a written condition of the sale. Use a Greek lawyer to check the title and confirm any past legalizations were properly filed. Transparency platforms such as Bektu exist to help foreign buyers vet developers and projects before committing, which complements but does not replace the engineer's certificate that Greek law specifically requires.

What is the bottom line?

If you try to buy a Greek property with undeclared illegal construction, the law simply will not let the sale complete until it is legalized, so the structure becomes the seller's problem to fix or yours to negotiate before closing. The dangerous version of this scenario is not secret ownership of an illegal building; it is sinking time and money into a purchase that stalls when violations surface, or taking on regularization costs you did not budget for. An engineer's inspection up front and the 2028 deadline on your radar turn this from a trap into a manageable checklist item.