Flood Zone (PPRI) in Nice: Rules for Extensions and New Construction | Cassini Expertise

Building or Extending in a Nice Flood Zone: A Strict Framework

The Var river basin and Nice’s coastal valleys expose several districts to flood risk. The flood risk prevention plan (PPRI), approved by prefectoral decree, classifies parcels into red zones (unbuildable), blue zones (buildable under conditions), or white zones (no specific requirements). Before any extension project, the first step is to check the regulatory zoning that applies to your parcel, available at the town hall and on the Alpes-Maritimes prefecture website.

This classification is binding on building permit decisions: an extension in a red zone will be refused, and an extension in a blue zone will only be granted if it complies with precise technical requirements.

Standard Requirements in Blue Zones

PPRIs across the Alpes-Maritimes share a set of recurring requirements for blue zones:

• habitable floor levels: the ground floor must sit above the reference elevation, calculated from the centennial flood level plus a safety margin; converting a basement or ground floor into habitable living space is prohibited;
• preservation of the flood expansion zone: limited backfilling and levee works, with access routes and evacuation paths kept clear;
• structural resistance: materials unaffected by water up to the reference elevation, structures anchored against hydrostatic pressure, and electrical and heating equipment installed above the reference level;
• building footprint: for extensions, the additional footprint is often capped and must not increase flood risk upstream or downstream.

Planning Documents and the Duty to Inform

The PPRI is a public-interest easement appended to the local urban development plan. Both sellers and landlords are legally required to inform buyers or tenants of the risks (duty to disclose risk information under Article L. 125-5 of the Environmental Code). A buyer who discovers after signing that their property is in a red zone has grounds to seek annulment or a price reduction if this information was not disclosed.

Extending a Property in a Blue Zone: How to Secure Your Project

The building permit application must include an explanatory note demonstrating compliance with PPRI requirements: the natural ground elevation, the reference elevation used, the planned floor levels, the materials selected, and any compensatory measures. The reviewing authority may seek an opinion from the DDTM (departmental territorial and maritime directorate) or the flood risk management service.

Common mistakes in permit applications include:

• underestimating the reference elevation: a floor raised only a few centimetres above existing ground level will be rejected if it does not meet the regulatory elevation;
• unauthorised conversion of floor space: converting a basement into a bedroom or office in a blue zone is a breach of the PPRI, punishable under criminal law (Article L. 480-4 of the Urban Planning Code) and may result in an order to restore the property to its original state.

Disputes and Litigation

Three types of disputes are most common:

• permit refusal on PPRI grounds: an informal appeal allows the project to be revised (reducing the footprint, raising floor levels, adjusting access routes); a formal appeal before the Nice Administrative Court must be filed within two months of the refusal notice;
• non-compliant extensions already built: a neighbour or the local council can seek demolition under Article L. 480-13; insurers will refuse to cover losses linked to non-compliance with the requirements;
• flood damage claims: once a natural disaster is officially declared, insurance experts assess the damage; a property built in breach of the PPRI may face a coverage exclusion, turning an insurance dispute into a construction liability case.

The Role of the Building Expert

Technical expertise provides decisive evidence in these cases: surveying actual elevations against the reference elevation, diagnosing damage following a flood, assessing the cost of bringing a property into compliance, and evaluating structural soundness after a flood event. In legal proceedings, the expert’s report forms the basis for compensation or demonstrates the compliance of a contested project.

Practical Recommendations

• request the PPRI extract and risk disclosure form from the town hall before signing any preliminary sale agreement;
• have the NGF elevation of the land and existing floor surveyed before designing the extension;
• have the PPRI compliance note validated by a professional before filing the permit application;
• keep all correspondence with the authorities and declare completed works as compliant.

Managing flood risk requires a rigorous approach from the earliest design stage. Complying with the PPRI is not an obstacle but a condition for the building’s long-term stability and insurance coverage. Any doubt about the regulatory zoning or technical compliance warrants consulting the relevant authorities or a building expert.

Cassini Expertise, a building expert based in Antibes, handles disputes related to PPRIs and flood damage in Nice, Cannes, Antibes and across the Alpes-Maritimes. Contact: 04 22 46 06 04.

📅 Mis à jour le 25/09/2026 — Cassini Expertise, expert bâtiment indépendant (06·83·13·40).