Disclaimer: This guide is for informational purposes only and does not constitute legal advice. Every PLU is specific to its commune and changes over time. 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. Always check current provisions on Légifrance and with your mairie before acting.
Last updated: August 2026.
Someone finds a plot. The map says "buildable zone," the listing says "terrain à bâtir," and the project takes shape in their head before they've even visited. They sign. Three months later, the zone règlement they never read tells them the height cap is one storey, the footprint ratio limits the house to a third of what they'd pictured, or half the plot has to stay permeable ground. The PLU said all of this from the start. This guide covers how to read it yourself, before signing, not after.
In 30 seconds:
The Plan Local d'Urbanisme is the document that fixes, plot by plot, what a commune (or a grouping of communes for a PLUi) permits to be built. It covers the entire municipal territory, no exceptions. Every parcel gets a precise designation, set out in Articles L. 151-9 and R. 151-17 to R. 151-26 of the Code de l'urbanisme.
In practice, checking your plot's zone is the first move before filing a déclaration préalable or a permis de construire. Misreading it can lead to a rejected permit, or worse, the demolition of a building already completed.
The Géoportail de l'urbanisme gives free access to the zoning and règlement for most French communes. The mairie's urbanisme department always holds the most current, legally opposable version, useful if there's any doubt or a recent revision. Some larger authorities, Paris among them, run their own portal.
Cadastre.gouv.fr lets you locate a specific parcel by its cadastral reference, handy for cross-checking against the zoning map.
This is where most people get lost. The zoning map is a colour-coded plan, with codes (U, AU, A, N) and sometimes hatching flagging easements. It tells you which zone your plot sits in. That's all it tells you.
The actual rules, height, positioning, density, exterior appearance, live in the written règlement attached to that zone. The règlement is traditionally structured in numbered articles: check Articles 1 and 2 first to see whether your project is permitted in principle, then Articles 6 through 10 to work out how to position it on the plot.
The zoning gives you the direction. The règlement gives you the decision. Reading one without the other is half the picture.
Urban zones (U): already built up and serviced. This is generally where a standard house gets built. Watch for sub-zones (UA, UB, UC...): a UA in a town centre often forces construction right up to the street line and shared walls, with taller allowances than a UB, a suburban extension zone with more flexible positioning.
Future urban zones (AU): land earmarked for eventual urbanisation, but not yet serviced. Some require a formal PLU modification before anything can be built; others are directly buildable under conditions. Check which applies before committing.
Agricultural zones (A): land protected for its farming potential. Construction is heavily restricted, generally reserved for agricultural operations.
Natural and forest zones (N): land protected for environmental value. Buildability is close to nil, barring narrowly defined exceptions.
A U zone doesn't automatically mean a workable project. The zone règlement can rule out certain uses, and easements or inadequate service connections can make a project technically unworkable despite favourable zoning.
Three figures come up again and again, and they're the ones that make or break a project on paper before anyone breaks ground.
Maximum height, given in metres or storeys (R+1, R+2). A standard suburban zone often caps out at R+1, while a dense town centre may allow more. On a coastline or inside a protected site, height can be restricted to preserve the architectural character, independent of what the zone allows elsewhere in the commune.
The footprint ratio (coefficient d'emprise au sol, CES), which sets the maximum buildable area relative to the plot's total surface. The maths is exact: an 800 m² plot with a CES of 0.25 caps your footprint at 200 m². Footprint is the vertical projection of any structure, exterior walls, enclosed outbuildings, and covered pools included. An open terrace or an uncovered pool generally doesn't count, but a carport on posts does.
The permeable-ground ratio (coefficient de pleine terre), which requires a share of the plot to stay unsealed, capable of absorbing rainwater. This figure shifts sharply between zones within the same commune, from 10% in an industrial zone to 40-50% in a dense residential one. It's often the most underestimated rule in a project, and the one that trips people up right at permit-filing stage.
These three figures compound. A generously sized plot can end up with a tiny actual buildable area once footprint and permeable-ground rules are applied together.
The zoning and règlement aren't the whole PLU. Annexes sit on top and can restrict a project independent of the zone itself:
A U zone that looks perfectly buildable on paper can still run into one of these. This is exactly what a certificat d'urbanisme confirms in writing, and makes legally binding.
A PLU isn't fixed. A commune can revise it, tighten an allowed height, raise a permeable-ground requirement, or reclassify a plot from AU into something more restrictive. Nothing stops you reading the PLU today, spending six months putting a project together, and finding the rules shifted underneath you in the meantime.
The certificat d'urbanisme exists for exactly this. A CUb issued by the mairie freezes the rules on your plot for 18 months, even if the PLU is revised during that window. Reading the PLU tells you what applies today. The CU gives you a written, legally binding guarantee it'll still apply tomorrow.
(See our full guide to the certificat d'urbanisme for the detailed mechanics.)
Reading a PLU alone can take time for an untrained eye, and the règlement never rewrites itself in plain language for you. It's a useful prospecting tool, not a legal guarantee.
The better move once a plot is seriously in the running: request a certificat d'urbanisme. It's free, it puts the mairie on the hook in writing, and it locks in the decision right when real money starts moving, before you sign the compromis de vente.