Foundation Encroachment: Court of Cassation Bans Refusal of Demolition

Imagine the scene: you have just bought a house in Beaumont-de-Lomagne, with a lovely garden. One day you decide to dig a swimming pool. And then, surprise: you come across concrete foundations protruding from your neighbour's property. He built his house ten years ago, and nobody had noticed. What to do? Can he be forced to demolish?

This question, which seems technical, touches on a fundamental principle of our law: the right of property is absolute, even underground. A famous decision of the Court of Cassation of 8 November 1978 (No. 77-13.563) ruled: an encroachment, even underground, justifies demolition. And this, even if the construction is otherwise perfectly compliant with planning regulations.

In short, your neighbour cannot hide behind a planning permission to keep his encroachment. But beware, not everything is so simple. Let us decipher this decision and its practical consequences together, in the light of practice in the Montauban area.

The facts: a story that happens every day

Mr X, owner in Beaumont-de-Lomagne, had a house built by the company Les Maisons Phénix. A few years later, his neighbour, Mr Y, notices that the foundations of this house extend beyond the boundary between their two properties. The encroachment is underground: it is not visible on the surface, but it is real. Mr Y demands demolition of the encroaching part.

The company Les Maisons Phénix and Mr X refuse. They put forward two arguments: firstly, the construction complies with the planning regulations; secondly, the encroachment is underground and causes no visible damage. The case goes to court.

At first instance (tribunal de grande instance), the judge orders demolition. But the Court of Appeal of Toulouse reverses this judgment: it considers that, since the encroachment is underground and the construction complies with planning regulations, there is no need to order demolition. Mr Y appeals to the Court of Cassation.

The Court of Cassation quashes the appeal judgment. It recalls that articles 552 and 545 of the Civil Code are clear: the owner of the land owns the subsoil, and no one can be forced to give up their property except for public utility reasons and upon payment of compensation. The encroachment, even underground, is a violation of another's property. The judge cannot refuse demolition on the grounds that the construction complies with the planning regulations.

The reasoning of the court — dissected

The decision of the Court of Cassation is based on two fundamental texts. Article 552 of the Civil Code provides that 'ownership of the land includes ownership of what is above and below'. In other words, when you own a piece of land, you also own everything that is in the subsoil, down to the centre of the Earth (in theory). Article 545 provides that 'no one may be compelled to transfer his ownership, except for public utility reasons and upon payment of fair and prior compensation'.

The Court of Appeal had made an error: it had considered that the underground nature of the encroachment and the planning compliance were sufficient to rule out demolition. But the Court of Cassation reminds it that the right of ownership is an absolute right: as soon as there is an encroachment, the aggrieved owner has the right to demolition, without having to prove any particular damage. This is what is called the 'real' nature of the action for demolition.

What few people know is that the Court of Cassation goes even further: it affirms that the judge cannot modulate the sanction. He cannot, for example, substitute damages for demolition, except with the agreement of the parties or in case of technical impossibility. In this case, the Court of Appeal had nevertheless considered that demolition was disproportionate. But the High Court said no: the right of ownership prevails.

However, beware: this decision does not mean that demolition is automatic in all cases. The encroachment must be proven and the aggrieved owner must take legal action. If the encroachment is minimal or if the owner has tolerated the situation for a long time (prescription of thirty years), demolition may be ruled out.

What this means for you — practically

For owner-occupiers: if you discover that your neighbour's foundations encroach on your land, even underground, you can demand demolition. Do not let anyone tell you that 'it is not serious' or that 'it is underground'. The case law is clear: your right of ownership is violated.

Let's take a concrete example. Imagine that you live in Montauban, rue de la République. Your neighbour has built an extension whose foundations protrude 30 cm onto your land. You wish to sell your house: the encroachment may constitute a hidden defect (latent defect) and reduce the sale price, or even lead to the cancellation of the sale. If you act quickly, you can obtain demolition at the neighbour's expense.

For landlord owners: if you rent out a property and an encroachment is found, it is up to the owner (you) to take action against the neighbour. The tenant has no standing to request demolition, but he can inform you and, if the encroachment disturbs him, ask for a rent reduction or termination of the lease.

For buyers: before buying a property, have a surveyor check the property boundaries and the absence of encroachment. If you buy a property with an undeclared encroachment, you could be forced to demolish it yourself, or face a demolition action from the neighbour.

In my practice, I have come across cases where the encroachment was underground and the aggrieved owner obtained demolition after years of proceedings. The cost of demolition can be high (several thousand euros), but it is the neighbour who must bear it.

Four tips to avoid this type of dispute

• Have a boundary survey carried out before any construction. The boundary survey (official delimitation of properties by a surveyor) is mandatory if your neighbour requests it. Even without obligation, do it to secure your project. Count between €1,000 and €2,500 depending on the area.
• Require a soil study and a foundation plan. Before pouring concrete, ensure that the foundations remain within your property. A simple glance at the plan can avoid a dispute lasting several years.
• Draft an easement agreement if the encroachment is unavoidable. If you need to go onto the neighbour's land for foundations, have an easement (real right) signed for free or for payment. This avoids any later challenge.
• If you discover an encroachment, act quickly. The limitation period (time limit to take legal action) is 30 years for real property actions. But the longer you wait, the harder it will be to prove the encroachment and obtain demolition. Consult a lawyer promptly.

Further reading: related case law and developments

The 1978 decision has been confirmed several times. For example, in a judgment of 10 March 1993 (No. 91-14.306), the Court of Cassation ruled that the encroachment of a building onto neighbouring land, even minimal, entitles the owner to demand demolition, without having to prove damage. More recently, in a judgment of 12 July 2018 (No. 17-22.590), it recalled that demolition is a matter of right, except in cases of material impossibility or agreement of the parties.

However, there is an exception: when the encroachment results from a good faith error and demolition would cause disproportionate harm compared to the benefit to the aggrieved owner. Some Courts of Appeal have sometimes substituted damages for demolition. But the trend of the Court of Cassation is firm: demolition remains the rule.

For the future, case law may evolve towards more proportionality, under the influence of the European Convention on Human Rights (right to respect for property). But for now, the principle remains: encroachment, even underground, justifies demolition.

Checklist before taking action

• Have I properly checked the property boundaries? Use a surveyor for an adversarial boundary survey.
• Do I have a bailiff's report? Have a report drawn up to prove the encroachment (photos, measurements).
• What is the time limit to act? 30 years from construction, but act as soon as discovered.
• Can I obtain damages instead of demolition? Only if the neighbour is in good faith and demolition is disproportionate, or if you accept a settlement.
• Should I inform my insurer? Yes, your legal protection insurance may cover the costs of proceedings.

Are you in a similar situation? A first 30-minute consultation with Maître Zakine (€45) could save you months of proceedings — and often much more. Book an appointment →