Have you added a room, converted a garage, or finished an attic without prior authorization? In France, it’s not uncommon—but it can become problematic. Thankfully, there are ways to regularize these unpermitted works and bring your property back into compliance.
Whether you plan to sell, rent, or simply sleep better at night, here’s what you need to know.
1. A Legal and Practical Obligation
In France, any construction or modification that alters the surface area or exterior appearance of a building must be declared to the municipality. If this step was skipped, your property is considered administratively non-compliant.
This can lead to several consequences:
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Complications during resale or inheritance,
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Insurance refusing to cover claims,
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Fines or legal action by the municipality (in rare cases, orders to demolish).
2. Yes, You Can Legalize It (But Not Always Automatically)
You may be able to submit a retroactive declaration to your local municipality. Depending on the size and nature of the work, this could be:
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A prior declaration of works (déclaration préalable) for spaces under 20 m² (or 40 m² in urban zones),
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A building permit (permis de construire) for larger areas.
Your file will need to include:
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Photos of the work,
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Floorplans and elevations,
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A technical description of what was built,
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Possibly an architect’s input (required if the total living space exceeds 150 m²).
⚠️ Please note: Legalization is not guaranteed. The municipality will only approve your request if the work complies with current urban planning regulations (PLU).
3. A Valuable Investment for the Future
Legalizing additional space allows you to:
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Increase your property’s value for sale or rental,
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Ensure full insurance coverage,
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Avoid delays in case of future transactions or renovations,
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Comply with short-term rental regulations, including the permit to rent (permis de louer).
4. Don’t Wait Until It’s Urgent
Legalization can take 1 to 3 months, depending on the municipality. That’s why we recommend starting the process early—especially if you’re planning:
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A sale,
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A refinancing or loan application,
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A change of use (e.g. converting to rental).
Working with an architect or a local real estate advisor can save time and help ensure the process goes smoothly.
In Short
Legalizing an undeclared living space protects your investment, boosts your property’s value, and avoids legal headaches down the line.
Not sure if your home is compliant? Wondering how to get started?
We’re here to help. Contact us and we’ll connect you with experienced professionals familiar with your local municipality and its urban planning rules.
