Disclaimer: This guide is for informational purposes only and does not constitute legal advice. French planning law depends on local rules specific to each commune. For any specific project, consult your local mairie's urbanisme department or a qualified professional. The author and dt-plans.com accept no liability for decisions made based on this content. The regulatory framework changes: check current provisions on Légifrance before acting.
Last updated: August 2026. This guide is reviewed annually.
Someone signs a compromis on a "buildable" plot. Six months later they find out about a right of way they never knew existed, or a heritage protection perimeter that kills any flat-roof plans stone dead. The PLU said all of this, in writing, across 300 pages of zoning code most buyers have neither the time nor the tools to decode. The certificat d'urbanisme exists to save you exactly this, free of charge, and almost nobody asks for one.
In 30 seconds:
The certificat d'urbanisme is an administrative document set out in Article L. 410-1 of the Code de l'urbanisme. In practice, it's the mairie confirming in writing what the local PLU means for your specific parcel, instead of leaving you to work it out yourself from a 300-page zoning document and its annexes.
It isn't compulsory. You can buy land in France without ever requesting one, the same way you can buy a used car without ever checking the service history. Both work fine, right up until they don't.
There are two versions, and mixing them up is the single most common reason people get burned.
The CUa (information certificate) sets out the rules that apply to the plot: PLU zoning, public easements, protected-heritage perimeters, and the local planning taxes. It doesn't rule on any specific project. This is the prospecting document, the one you request while you're still deciding whether a plot is worth pursuing.
The CUb (operational certificate) goes further. You describe your project, even in outline, and the mairie tells you whether the plot can take it, factoring in access to existing or planned services (water, drainage, electricity, road access). It comes back positive, positive with conditions, or negative. This is the decision document, the one you request once you've settled on a plot and roughed out a project, right before you sign anything.
The practical rule: CUa while you're still scouting, CUb once the plot is chosen and the project has a rough shape, before the compromis. Asking for a CUb on a project that's still vague is asking the mairie to hand you a free rejection.
The clock starts when the mairie receives a complete application, filed on form CERFA 13410. One month for a CUa, two months for a CUb. If the file is incomplete, the mairie has the same window to request the missing pieces, which pauses the clock until you provide them.
File in multiple copies depending on type and location: 2 copies for a CUa (3 near a listed monument, 4 inside a national park core), 4 copies for a CUb (5 and 6 under the same conditions). Add two more months to either timeline if the plot sits inside an ABF perimeter (a listed monument, a protected site, a ZPPAUP). On a plot near a Breton village centre with a classified church 200 metres away, that isn't a hypothetical.
If the deadline passes with no written response, the certificate is deemed granted by default. That tacit certificate only locks in three things: the applicable planning rules, any administrative restrictions on the property, and the list of taxes and contributions due. The mairie is still required to send a written response eventually, even late. Go back and request it: the silence gives you the right, the written attestation gives you proof of it the day someone tries to argue otherwise.
This is the part most people miss entirely, and it's the only serious reason to get a CU before committing to a plot.
For 18 months from the date it's issued, the planning rules applying to your parcel are frozen exactly as they stood on that date, even if the commune revises its PLU in the meantime. Buy a plot in a buildable zone in January, watch the commune tighten height limits or footprint ratios in June, and your CU still protects you. The rules that apply are the ones from the day the certificate was issued, full stop.
The logical exception: public-utility easements and safety or public-health rules are never frozen. Nobody gets to sell you the right to build on land that turns dangerous.
A second, lesser-known protection: if a droit de préemption (a right of first refusal for the commune) gets set up on your plot after the CU is issued, the commune can't exercise it while your certificate stays valid. In practice, the mairie can't change its mind halfway through and pull the rug out.
The certificate can be extended for a further year, but the request has to land at least two months before the original 18 months expire, on plain paper, in two copies, alongside the original certificate. The extension is only granted if the rules, easements, and taxes on the plot haven't changed since it was issued.
The CU is not a building permit. A positive CUb says your project is feasible in principle, not that it's authorised. You'll still need to file a déclaration préalable or a full permis de construire depending on the scope of the work, with a complete file, and that process runs independently.
A positive CUb also doesn't guarantee your eventual permit sails through without conditions. It guarantees the rules stay stable while the CU is valid, not that there'll be zero back-and-forth on the finished project's details when the permit application actually lands.
And a CUb can come back negative. At that point you have two options: adjust the project to address the reasons for refusal, or challenge the decision at the tribunal administratif within two months of notification. A recours gracieux to the mayor, tried before any legal challenge, sometimes gets the decision reconsidered without needing a judge at all.
The request goes on form CERFA 13410, it's free, and it's filed either at the mairie or through the commune's online portal. Anyone can request one, not just the owner: a prospective buyer, a notaire, an estate agent. Worth knowing if you're negotiating quietly: when the mairie issues a CU to someone other than the owner, it doesn't notify the owner that the request happened.
The right timing is before you sign the compromis de vente, once you've got a real project in mind rather than a vague idea. That's exactly what a CUb is for, locking down the decision that's about to commit real money.
On the ground, the difference between reading a PLU alone and holding the mairie's written answer is the difference between guessing and knowing. The PLU is the general rulebook; the CU is that rulebook applied to your specific parcel, signed by the same authority that will later issue the permit. The two aren't redundant, they're sequential: understanding the PLU tells you what to ask for, the CU gives you the answer you can actually rely on.