The extension of a house overruns the neighbouring plot by 4.653 m², on a plot of 1,622 m². Two living rooms, a building permit, a building older than the neighbours’ purchase: the Court of Appeal holds demolition disproportionate. The Cour de cassation (the French supreme court for civil matters) quashed on 3 July 2025, in line with its settled case law: an owner whose land is encroached upon is entitled to have the encroachment removed, whatever its area and cost. No compensation can be imposed on them instead. That leaves the author of the encroachment a single way out, buying the strip, and that is where the question of price arises.
The facts
By deed of 6 November 2006, a couple bought a plot and an undivided half of another, adjoining their neighbours’ plot. They sued the neighbours for a court-ordered boundary survey; the appointed expert filed his report, and they sought its approval together with the demolition of the extension of the neighbouring house encroaching on their land.
On 1 December 2022 the Nîmes Court of Appeal refused demolition: the judge must carry out a proportionality review between demolition and the encroacher’s right to respect for their home; the encroachment covered 4.653 m² of a 1,622 m² plot, in line with a party wall, and consisted of a building containing two living rooms of the neighbours’ home, built under a building permit and before the claimants bought their land; demolition would be a disproportionate sanction. It even granted the neighbours a right of passage and ladder access to render the wall of the extension.
The decision
The Cour de cassation quashed (Cass. 3e civ., 3 July 2025, appeal no. 23-12.925), under article 545 of the French Civil Code: “no one may be compelled to give up their property, except for public purposes, and against just and prior compensation” (translated from the French).
It restated its case law: “every owner is entitled to obtain the demolition of a structure encroaching on their land, without their action being capable of amounting to fault or abuse”. The encroacher can rely neither on the right to peaceful enjoyment of possessions, since their structure infringes that of the victim, nor usefully on the right to respect for their home: the interference constituted by eviction and demolition “aims to guarantee the owner of the land the right to respect for their possessions”, and, “eviction and demolition being the only measures capable of allowing the owner to recover the fullness of their right over the property, the resulting interference cannot be disproportionate having regard to the seriousness of the infringement of the right of property”. Having found an encroachment, “even one carried out by a building that may be regarded as a home”, the Court of Appeal had to “order any measure capable of putting an end to it”.
What this changes for the valuation
No compensation instead of demolition. Article 545 prohibits turning an encroachment into a private expropriation: the judge cannot order the encroacher to compensate the neighbour while leaving them the strip. In such a dispute, the expert therefore does not quantify a “value of the encroached strip” to be imposed on the victim. What he quantifies, if instructed, are the ancillary losses: loss of enjoyment of the area during the encroachment, temporary loss of value, cost of restoring the land after demolition.
The amicable sale, and its price. The only way out for an encroacher who wants to keep their two living rooms is to buy the strip from the neighbour, who remains free to refuse. The price of such a sale is not the price of land per square metre: for a few square metres that save a house, the seller may ask a premium price (valeur de convenance), far above the market value of the area, and the courts do not hold it against them. The expert establishes a reasoned range: the value of the area sold from references in the area, the loss of value of the selling plot (area, residual building capacity, setback from the boundary), and, on the other side, what the buyer saves by avoiding demolition, cost of works and loss of value of their house. The premium price is negotiated between those two bounds, and a report documenting them saves time for both parties and their notaires.
The boundary survey first. The case began with a court-ordered boundary survey, and it was the licensed surveyor’s report that established the encroachment at 4.653 m². No valuation is useful until the boundary is fixed; before buying built land on a boundary, a joint boundary survey costs less than a lawsuit.
A lawful building is no protection. The building permit, the age of the building and its alignment with a party wall carried no weight. For a buyer, a structure on a boundary is a point to check against the title and the plan before signing, like the floor area or easements; a reservation in the deed, or a discount, may be justified as long as the boundary is uncertain.
What the expert takes from it
- An encroachment, however small, even on a home, even built with a permit, gives a right to demolition; no compensation can be imposed on the neighbour instead.
- The negotiated way out is the sale of the strip, at a premium price the neighbour is free to set.
- The expert documents the two bounds of that price: value of the area and the seller’s loss, the buyer’s saving.
- The ancillary losses of the encroachment, enjoyment and restoration, are quantified too.
- The boundary survey precedes any valuation; on a boundary, it precedes the purchase.
Further reading
The Market value page describes the assignment, its timescale and its fee. The glossary entries comparable and préjudice immobilier complement this article. On the same theme: Right of way and enclosed land: one indemnity per dominant estate and Nuisance and loss of view: not automatic. The decision is available on Légifrance.
What next
Does a neighbour's building encroach on your land, or yours on theirs?
I value the strip of land concerned and the premium price an amicable sale can justify, from the boundary survey and references in the area, to avoid demolition or to negotiate it.
Free quote, by email or by phone. No commitment before the quote is accepted. Fees are never linked to the value of the property (Charte de l’expertise, Title I, §2.1).
