Short answer. Prescription is based on the possession. Article 1135 provides that where the adverse claimant possesses by mistake an area greater or less than that expressed in his title, prescription shall be based on the possession. The words carrying the weight are by mistake.
What the law says
In case the adverse claimant possesses by mistake an area greater, or less than that expressed in his title, prescription shall be based on the possession.
Civil Code, Article 1135 — Possessing More Land Than the Title Shows. Read the full provision →
The rule follows the ground, not the paper
Titles and fences disagree more often than people expect, and the article picks a side. Where the areas differ, prescription shall be based on the possession, which means the claim is measured by what was actually held and worked rather than by the figure recited in the instrument. That is a sensible rule for prescription, which is a doctrine about facts on the ground. Note the limit, though: the article governs what prescription is based on. It does not by itself enlarge the title, and the two remain separate questions.
“By mistake” is the condition
The provision contemplates a claimant who genuinely believed the area he occupied was the area he had — the fence went where an old boundary ran, the neighbour's corner was never marked, the survey was inaccurate from the beginning. It is not written for someone who knew the extent of his title and extended his occupation anyway. That distinction is factual, and it is proved by how and when the excess came to be occupied rather than by anyone's later account of his own state of mind.
It cuts against you as readily
The article is symmetrical, and the less favourable half is easy to overlook. It applies equally where the area possessed is less than that expressed in his title, so a claimant relying on prescription for a parcel he never fully occupied gets only what he held. Someone whose title recites a thousand square metres but who has fenced and worked six hundred cannot use prescription to reach the remainder. If your claim to the whole rests on the document rather than on the ground, this is not the provision that helps you.
The survey decides it
Have the property relocated by a licensed geodetic engineer against the technical description in the title, so that the difference is measured rather than asserted. Then date the occupation of the excess: old photographs, the age of the fence or of the trees along it, tax declarations, and neighbours who can say when the line was established. Article 1118 still requires possession in the concept of an owner, public, peaceful and uninterrupted, and that has to be shown for the excess area as much as for the rest.
Related provisions
- Civil Code, Article 1118 — Possession That Ripens Into Ownership
- Civil Code, Article 1137 — Extraordinary Prescription — 30 Years