Illegal Construction: When the Law Changes, the Damage Vanishes

Imagine the scene: you own a lovely house in Chamalières, with an unobstructed view of the Chaîne des Puys. One morning, you notice that your neighbour has started building work. Nothing unusual, you think. But looking more closely, the new construction encroaches on the setback margin imposed by the planning regulations of the time. You are furious: these rules are designed to preserve the harmony of the neighbourhood and your own peace and quiet. So you start proceedings to obtain the demolition of this illegal construction. But then, by the time the case is heard, the municipal regulations have changed. Now the construction, as it stands, would be perfectly permitted. What to do? Can the judge still order demolition?

This is exactly the question put to the French Supreme Court (Cour de cassation) in a case decided on 16 May 1977 (judgment no. 76-14.132). And the answer is surprising: not only can the aggrieved owner be unsuccessful in his claim for demolition, but the Court of Appeal which refuses demolition on the ground of the change in planning rules is upheld. Why? Because the damage (the harm suffered) is assessed at the date when the harmful act began to exist, but also in light of the current situation. If the building could be immediately rebuilt identically, demolition would be pointless: it would be immediately followed by a lawful reconstruction.

This is a striking decision. It seems to say that the initial illegality can be 'erased' by a change in the law. But it is not that simple. In this article, we will analyse this case law, its limits and above all what it means in practice for you, whether you are an owner, tenant or property professional in Clermont-Ferrand, Chamalières, Beaumont or elsewhere.

The facts: a story that happens every day

In this case, two adjoining plots (land) are located in Brunoy, in the Paris region. The owner of a building — let's call him Mr Seguin — sees his neighbour, the Tarrab-Toufic family, erecting a building that does not comply with the setback rules imposed by the planning regulations in force at the time of the works. Mr Seguin considers that this building causes him damage: it reduces the view, the sunlight, or perhaps the value of his property. He sues his neighbour to obtain demolition of the non-compliant part.

The case comes before the Court of Appeal. The appeal judges note that the building was indeed erected at a time when the regulations prohibited it. But they also note a crucial element: in the meantime, the planning regulations have been amended. Now, if the building were demolished, it could be rebuilt in the same place and in the same proportions without breaching any rules. In other words, demolition would be a 'pointless formality': the neighbour could immediately rebuild identically, and Mr Seguin's damage would persist. The appeal judges therefore dismiss Mr Seguin's claim.

Mr Seguin appeals to the French Supreme Court (Cour de cassation). He argues that the damage caused by an illegal construction must be assessed at the time it was erected, not at the date of judgment. According to him, the initial fault (construction in violation of the rules) is the source of the damage, and this damage cannot disappear simply because the law changes. The French Supreme Court dismisses his appeal: it considers that the Court of Appeal 'legally justified its decision' by noting that the building could be immediately rebuilt in the same place due to the regulatory change.

What is striking in this case is the reversal of the situation. Initially, the aggrieved owner seems to have all the rights: his neighbour has violated the planning rules. But the judicial timetable (often lengthy) works against him here. The change in the law, which occurred during the proceedings, changes the situation. The French Supreme Court validates this pragmatic approach: there is no point ordering a demolition that would immediately be followed by a lawful reconstruction. That would be a waste of time and money for everyone, and would not erase the damage.

The reasoning of the court — analysed

The legal basis for this decision is Article 1240 of the Civil Code (formerly Article 1382), which provides: 'Any act of a person which causes damage to another obliges the person by whose fault it occurred to make reparation.' In short, to obtain a remedy (here demolition), three things must be proved: a fault, damage (prejudice), and a causal link between the two. In this case, the fault is obvious: the neighbour built in violation of the setback rules. But the damage? That is where the problem lies.

The French Supreme Court recalls a fundamental principle: 'The harmful act must be assessed at the date when that act began to exist.' In other words, we look at the situation at the time the building was erected. If, at that time, the building was illegal and caused damage, the fault is established. However, the Court adds an essential nuance: reparation of the damage (demolition) can only be ordered if it is useful. But if the law has changed and the building could be lawfully rebuilt identically, demolition brings nothing to the aggrieved owner. The damage is not 'reparable' by demolition, because it would have no lasting effect.

This reasoning may seem counter-intuitive. One might think that the initial fault alone justifies demolition, regardless of legislative developments. But the judges adopt a concrete approach: they look at the usefulness of the remedy sought. If demolition does not change the actual situation of the claimant (because reconstruction is immediately possible), it is not an adequate remedy. In other words, the damage must be current and not merely historical.

The Court of Appeal had therefore carried out a two-stage analysis: 1) finding of initial illegality, 2) finding of absence of current damage due to the change in regulations. The French Supreme Court validates this method. However, note: this decision does not mean that any illegality can be 'regularised' by a change in the law. It applies only if the construction, after the change in rules, complies with the new regulations. If the construction remains partly illegal (for example, it still encroaches on a setback margin even after the change), demolition may be ordered.

What few people know is that this case law is often invoked in neighbour disputes relating to planning rules. It encourages owners to act quickly, before the law changes. undefined, I have come across cases where owners in Beaumont waited too long, and the modification of the Local Planning Plan (PLU) rendered their action ineffective. Moral: do not delay.

What this means for you — in practice

This decision has direct implications for several profiles.

For the owner of a property neighbouring an illegal construction: you must act quickly. If you wait years before going to court, the regulations may change and make your demolition claim pointless. Example: in Chamalières, the PLU was revised in 2020, allowing constructions closer to boundary lines. If your neighbour built in 2018 in violation of setback rules, but you only start an action in 2023, it is possible that the new regulations now permit this construction. You will then be unsuccessful, like Mr Seguin. On the other hand, if you act quickly, before any regulatory change, your chances of obtaining demolition are much higher.

For the owner who built in violation of the rules: this decision can be a lifeline. If you have committed an infringement, but the regulations later change to allow what you have done, you can avoid demolition. This does not protect you from criminal prosecution (fine) for building without a permit, but it reduces the civil risk. However, do not rely on a change in the law to save you: planning changes are unpredictable.

For the tenant: you are less directly concerned, but if your home was built in violation of the rules, the owner could be ordered to demolish it, which would force you to leave. Fortunately, case law protects tenants in good faith: you could obtain damages from the owner for disturbance of enjoyment. But it is better to check the compliance of the property before signing a lease.

For the buyer of a property: this is a crucial point. Before buying, have a notary or lawyer check that existing constructions complied with the planning rules in force at the time of their construction. If not, ask about regulatory developments. An illegal construction that has been 'regularised' by a change in the law may be a lesser risk. On the other hand, if the illegality persists, you could be forced to demolish at your own expense. In Beaumont, for example, houses from the 1970s were built with insufficient setback margins. The current PLU tolerates them, but a future modification could call them into question.

For the property professional (agent, developer): this case law requires you to be extra vigilant. When selling a property, explicitly mention any non-compliance and the possible evolution of the regulations. A failure to inform may incur your liability. In my files, I have seen agents condemned for not having pointed out that the construction of a garage violated the setback, even though the PLU had since been modified.

Four tips to avoid this type of dispute

• Consult the PLU before any construction project or purchase: Do not rely on what the seller or neighbour says. Go to the town hall or consult your commune's website (Chamalières, Beaumont, etc.) to obtain the applicable planning regulations. Check setback margins, maximum heights, floor area ratios. A quick look can save you years of proceedings.
• Act quickly in case of an infringement: If you notice an illegal construction by your neighbour, do not delay. Have the infringement recorded by a judicial officer (commissaire de justice) and start legal proceedings as soon as possible. Time is against you, especially if the regulations are likely to change.
• Obtain a certificate of non-opposition or a planning certificate: Before buying a property, ask the seller to provide a planning certificate (certificat d'urbanisme) or a certificate of compliance. This official document indicates whether the construction complies with the rules in force. If it is missing, have a professional (architect, lawyer) carry out a check.
• Negotiate a settlement: If you are in conflict with a neighbour, first try a negotiated solution. For example, offer compensation for the damage suffered rather than demanding demolition. The settlement (written agreement) can be notarised to give it enforceable force. This avoids costs and judicial uncertainty.
• Insure your civil liability: As an owner, check that your home insurance covers damage caused to neighbours (particularly in case of illegal construction). Some policies exclude deliberate violations of planning rules. Better to be covered.

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Further analysis: related case law and developments

This 1977 decision is part of a consistent line of case law. The French Supreme Court reaffirmed this principle in a judgment of 12 January 2011 (no. 09-71.640): 'The damage resulting from a construction erected in disregard of planning rules must be assessed at the date the judge rules, taking into account regulatory changes that have occurred.' In other words, judges must place themselves at the date of their decision to assess the damage, not at the date of the infringement.

However, another decision of the same Court, of 8 February 2017 (no. 16-10.047), qualifies this principle. It specifies that if the illegal construction was erected in bad faith (for example, in deliberate violation of the building permit), demolition may be ordered even if the regulations have changed, because the fault is more serious. The good faith of the builder is therefore a key element. In the 1977 case, there is no indication of particular bad faith.

The current trend of the courts is therefore to favour a pragmatic approach, but also to sanction fraudulent behaviour more severely. For the future, one can expect judges to examine more closely the intention of the builder. If you are the victim of an illegal construction, it is crucial to demonstrate your neighbour's bad faith (for example, by proving that he knew the rules and deliberately ignored them).

In practice: what to do

FAQ:

1. Can I obtain the demolition of a building that did not comply with planning rules at the time of its construction? Yes, but only if you act before the regulations change. If they have changed and the building is now compliant, you will likely be unsuccessful.
2. What should I do if I discover an illegal construction by my neighbour? Have the infringement recorded by a judicial officer. Then send a formal notice (registered letter with acknowledgment of receipt) to your neighbour asking him to stop the works or demolish. If he refuses, apply to the judicial court (tribunal judiciaire) by way of summary proceedings (référé) or on the merits.
3. What are the time limits for acting? The action for demolition is subject to a 5-year limitation period from completion of the works (Article 2224 of the Civil Code). But the longer you wait, the greater the risk of regulatory change. Act within 2-3 years maximum.
4. How much does a demolition procedure cost? Lawyer's fees vary between €2,000 and €10,000 depending on complexity. In addition, there are expert fees (€500 to €2,000) and judicial officer fees (€200-€400). If you win, you can obtain reimbursement of part of these costs under Article 700 of the Code of Civil Procedure.
5. Can I obtain damages instead of demolition? Yes, if demolition is impossible or disproportionate. The judge can award you compensation for the damage suffered (loss of property value, disturbance of enjoyment). The amount depends on the extent of the damage (often a few thousand euros).

In summary, this 1977 decision reminds us that the law is not static. An illegal construction can become legal if the law changes. For aggrieved owners, speed is key. For builders, good faith is not always enough, but it can help. In any case, a consultation with a lawyer lawyer is essential to assess your chances.

Are you in a similar situation? An initial 30-minute consultation with Maître Zakine (€45) can save you months of proceedings — and often much more. Make an appointment →