Dry Stone Fence Encroaches on Neighbor: GNSS Survey in Toulon

PROPERTY — FRENCH RIVIERA

You bought a house in Toulon, in the La Garde district. The dry stone wall bordering your garden has always seemed a bit crooked. One day, your neighbor shows you a cadastral plan on his phone: according to him, your wall encroaches 12 centimeters onto his property. You measured with a tape measure, checked on Géoportail (French online mapping service), but nothing is clear. 12 cm seems trivial, but for property rights, it’s a chasm.

What You See — and What It Really Hides

The wall is old, made of dry stones, without a concrete foundation. It follows a line you thought was the boundary. But the cadastre has no legal value for boundary marking. What you see is a wall that may have moved over time, or was built crooked 50 years ago. Honestly, without a precise topographical survey, you can’t assert anything.

What no one says: a tape measure or phone GPS gives an uncertainty of 5 to 10 meters. Not enough. For a boundary dispute, centimeter accuracy is needed. On a case in Toulon last year, I measured an encroachment of 8 cm with a GNSS RTK: the owner had lost 3 m² of land without knowing it. Here, 12 cm over 20 meters of wall represents 2.4 m². Not negligible.

The Calculations That Change Everything

To measure the encroachment, we use a GNSS RTK with centimeter accuracy. The standard NF ISO 17123-8 (French standard for GNSS surveying procedures) defines the procedure: we station on a known point (IGN benchmark or calibration point), then measure the ends of the wall. The measurement uncertainty (RMS) is calculated as follows:

RMS = √(σ₁² + σ₂²) with σ₁ = 1 cm (RTK planimetric accuracy) and σ₂ = 0.5 cm (centering error). So RMS = √(1² + 0.5²) = 1.12 cm.

The tolerance for judicial boundary marking is 2 cm according to the decree of September 16, 2003 (French regulation). Here, the measured encroachment is 12 cm, well beyond the tolerance. Concretely, the wall must be moved or an easement of passage must be negotiated. Article 646 of the French Civil Code allows any owner to demand boundary marking of their property. Article 647 specifies that fences must respect boundaries. In Toulon, the High Court (Tribunal de Grande Instance) rules on these disputes.

What Happens If You Do Nothing

Time works against you. In the Alpes-Maritimes region, clay soils swell with rain and shrink in summer. Your dry stone wall, without foundation, can move even more. Within 2 years, the encroachment could reach 20 cm. And the neighbor can initiate a judicial boundary action: you will have to pay the expert fees (€2,000 to €5,000) and also demolish the wall.

I saw a case in Toulon where an owner waited 5 years: the wall had tilted an additional 15 cm, vegetation had grown between the stones, and the restoration bill reached €8,000. Not to mention legal fees. Acting now saves time and money.

Recourse and Guarantees: What You Can Demand

You can demand an amicable boundary marking. Send a registered letter with acknowledgment of receipt to your neighbor, proposing to call a surveyor (expert en urbanisme). If they refuse, file a claim with the court in Toulon. Article 646 of the French Civil Code grants you this right. The standard NF ISO 17123-8 guarantees the reliability of GNSS measurements. An independent expert like Cassini Expertise can carry out the contradictory survey and provide a report usable in court. Do not delay: the 30-year statute of limitations runs, but the longer you wait, the more complicated the situation becomes.

📅 Mis à jour le 31/07/2026 — Par Cassini Expertise, expert bâtiment indépendant 06 & 83. Devis gratuit : 04 22 46 06 04.

Questions fréquentes

What is a dry stone fence?

A dry stone fence is a wall built without mortar, using stones carefully stacked together. It relies on the interlocking of stones for stability and is common in rural and historical landscapes.

Can my neighbor build a dry stone fence on the property line?

Generally, property lines must be respected. Building exactly on the boundary may require a shared agreement or survey. If the fence encroaches on your land, you have legal recourse.

How does a GNSS survey help in boundary disputes?

A GNSS survey uses satellite positioning to determine precise coordinates of property corners. It provides accurate evidence to establish the true boundary line, helping resolve disputes over encroachments.

📅 Mis à jour le 19/09/2026 — Cassini Expertise, expert bâtiment indépendant (06·83·13·40).