Building and extending a home are important projects for many homeowners. It is essential to take into account the risks, especially those related to floods. I live in a flood zone, what are the regulations? Our answers.
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Flooding is a serious threat that can cause significant damage to homes and endanger the lives of residents. Not everything is allowed in areas at risk of flooding. Risk prevention and management measures must be taken into account.
What is a flood zone?
A flood zone is a geographical area that is susceptible to flooding during periods of heavy rainfall, river flooding, rising marine waters or other similar phenomena.
These areas may be located near rivers, lakes, coasts or other areas where water accumulation may occur.
The classification of an area as floodable is generally based on hydrological and hydraulic studies that present flood risks, including analyzing water levels, flows and topographical features of the area.
The identification of these areas is essential for urban planning.
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How do I know if my house is in a flood zone?
The Flood Risk Prevention Plan (PPRI):
- Delineates areas at risk of flooding.
- Determines hazards for exposed areas and allows for specific land-use bans or requirements so as not to aggravate the risk.
- Defines the urban planning rules to be respected in flood zones in order to limit buildings and sensitive activities at risk.
These appropriate prevention and protection measures are intended to ensure the safety of residents and reduce the costs associated with flood damage.
The PPRI may include recommendations or obligations regarding safety devices (, dams, etc.), alert procedures, evacuation plans, etc.
The Flood Risk Prevention Plan defines 3 regulatory danger zones:
- A regulatory area of strong hazard.
- A regulatory area of medium hazard.
- A regulatory area of low hazard.
If you are concerned by the flood risk, the possibilities of construction and extension will be regulated according to the hazard. The greater the hazard, the less possible the possibilities of construction or extension.
The decision to define a flood zone is generally the responsibility of the competent public authorities, such as State services (Regional Environment Directorate, Planning and Housing, Departmental Directorate of Territories, etc.) and local authorities (town halls, departmental councils, etc.) and bodies dedicated to the management of natural risks (water commissions, risk prevention organizations, etc.).
These decisions are based on hydrological, topographic and meteorological studies, as well as historical flood and flood risk data. The reference rating is often the hundred-year flood plus a safety margin.
The flood risk is a public utility easement. This means that the State can restrict the right to property for the purpose of public utility.
You can check if your parcel is located in a flood zone at the following sites:
https://www.georisques.gouv.fr/
https://errial.georisques.gouv.fr/#/
Can I be refused a building permit in a flood zone?
Any work project, a construction or an extension, will be analyzed according to:
- The Flood Risk Prevention Plan (PPRI).
- The Local Urban Plan (PLU).
- From the Communal Map.
- The National Urban Planning Regulations according to the situation of your municipality.
The extension project must comply with the PPRI. HighwayStarz / highwaystarz - stock.adobe.com
If your project does not comply with the PPRI, your building permit may be refused, hence the importance of consulting it beforehand.
The PPRI may regulate the following:
- The footprint of the buildings in order to have a lesser impact on the area.
- The floor rating of the first floor of the dwelling. For example, at least 20 cm above the reference dimension of your plot.
- Power grids must be out of water.
- The materials used under the reference number. They will have to be insensitive to water.
- Waterproofing measurements will be taken into account under the reference rating.
It will be advisable to locate the construction in a non-flood zone if your plot includes an area not exposed to risk.
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Can I renovate or extend my house if it is located in a flood zone?
Maintenance and maintenance work on buildings is permitted in flood-prone areas as well as internal developments, the creation of additional floors and the creation of new openings.
Extensions will, like new constructions, be limited in footprint and subject to planning permissions:
- A prior declaration of work must be filed for any project between 5 and 20 m² (up to 40 m² in the case of an extension in an urban area of a local urban plan and provided that it does not exceed 150 m² of total floor area).
- A building permit must be filed for any project exceeding 20 m² (or 40 m² in the case of an extension in urban areas of a Local Urban Plan).
But you must always refer to the PPRI applicable in your municipality. The latter may impose specific restrictions or prohibitions.
In addition, it will be necessary to carry out your extension in compliance with the requirements common to the constructions (floor dimension, electrical networks excluding water, materials and waterproofing measures) set out in the previous paragraph.
Good to know
All extensions are listed, and often, the possibilities of extension are appreciated at the date of approval of the PPRI. If you have the right to 30 m² of extension for example and you have built a garage of 20 m² since the approval of the PPRI, you only have 10 m² of extension left that can be authorized in flood zone.
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How to challenge a flood zone?
If you wish to contest the classification of your plot as a flood zone, two remedies are open to you. The amicable way must always be preferred.
The amicable way before the authority in charge of flood zones of your department
To contest the decision, you must follow these steps:
- Gather information about your plot: maps, topographic surveys, hydrological survey data, historical flood data.
- Find out about current legislation on the status of a flood zone.
- Consult with experts in geology, hydrology or engineering for an independent assessment of the flood zone.
- Prepare your argument based on the information you have gathered. Highlight elements that contradict the existing classification.
Send your detailed dispute file to the competent authority. Attend meetings or hearings when you are called.
Good to know
The challenge process may vary from one jurisdiction to another. For example, in Sarthe, it is the Departmental Directorate of Territories. Check with your town hall to find out who to contact or with a specialized lawyer.
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How do I insure my home in a flood zone?
It is necessary to inform your insurer if your property may be flooded so that the damage is taken into account in case of flooding.
My home is built legally
Check that your home complies with the rules and regulations in force for construction in a flood zone.
Inform your insurance company of the situation of your property and provide all documents proving the legality of the construction.
Get home insurance that covers flood damage.
Make sure you understand the terms and limitations of your insurance policy, if necessary do not hesitate to ask your insurer.
Take preventative measures to reduce the risk of flooding, such as installing proper drainage systems, pumps or other flood protection devices.
My home is an illegal construction
Insurance companies may refuse to cover homes built illegally in flood zones. In some cases, they may even cancel existing insurance policies.
Consult a lawyer specializing in construction law to assess your legal situation and determine the actions to be taken.
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Bear in mind
Special attention should be paid to the construction and extension of houses in areas at risk of flooding.
Risk prevention, careful planning and the use of appropriate construction techniques are essential to ensure the safety and sustainability of homes.
Complying with local planning regulations and consulting experts for advice specific to your situation are essential.
By taking these precautions, you will be able to build or expand your property while minimizing the risks associated with flooding and ensuring the protection of your investment and your family.