What do the U, AU, A and N zones of a PLU mean?
A PLU places every parcel in an urban zone (U), a future development zone (AU), a farmland zone (A) or a natural and forest zone (N). U zones in principle take buildings; in A and N zones, building is the exception, but an existing house can often be extended or given an outbuilding if the rules allow it. The zone’s name is not enough: the rules for that zone set the limits, and the mairie applies them to each application.
The four families of zones
The Urban Planning Code defines four families (arts R151-18 to R151-24). Each commune then divides them into sub-zones with its own letters and numbers: UA for an old centre, UB or UC for more recent districts, 1AU or 2AU for sectors to be opened up, Ah or Nh for hamlets. The legend of the zoning map gives their exact meaning.
| Zone | What it covers | For an existing house |
|---|---|---|
| U (urban) | Areas already built up, or with enough utilities for new buildings | Extensions and outbuildings in principle possible, within the rules |
| AU (future development) | Areas intended to be opened up for building, sometimes after the PLU is amended | Depends on the rules; often tied to an OAP or a wider scheme |
| A (farmland) | Land protected for its farming or economic potential | New buildings very limited; extensions and outbuildings only if the rules provide for them |
| N (natural and forest) | Areas protected for their landscape, habitats or hazards | Same limits as in zone A, sometimes stricter |
A house’s planning rules are read together with other documents, such as extending a house and the planning certificate. You can see how a dossier brings them together for one address in the sample dossier.
A house in an A or N zone
Many country houses are in an A or N zone, which often surprises buyers. The classification does not make the house unlawful: it can be lived in and maintained. It does, however, limit what can be added. The code lets the rules allow extensions or outbuildings for existing homes, provided they set the height, siting and density (art. L151-12 of the Urban Planning Code). If the rules do not provide for this, there is very little room.
Service-public.fr points out that farmland zones are not open to building, apart from projects strictly governed by the PLU rules, and that all of them still need planning permission. A change of use, for example turning a barn into a home, also requires the building to be designated for this in the PLU.
A house in a U or AU zone
In a U zone, the rules govern projects rather than forbid them. The articles that matter most to a buyer are siting (distance to the street and to the side boundaries), ground coverage, height, the look of façades and roofs, parking and the share of green space. A plot that seems large may offer little room if ground coverage is low or if the house already reaches the required setbacks.
In an AU zone, it depends on whether the sector has been opened up. A 1AU zone is often buildable as utilities arrive or under an OAP; a 2AU zone usually awaits a change to the PLU. A neighbouring plot in an AU zone may therefore look very different in the coming years.
What can be built on the land next door
The zone’s rules decide
Two parcels zoned UB in two neighbouring communes do not have the same rules. Even within one commune, a sub-sector can change the height or the ground coverage. So always read the rules of the exact zone, the general provisions at the start of the document, and the requirements on the zoning map for the parcel.
For a specific project, only the mairie can say, when an application is made, whether it complies with the rules. Before buying, an operational planning certificate gives a written answer on whether a described operation is feasible.
Finding the PLU and zone of an address
What a buyer can check for themselves
- The parcel’s zone and sub-zone, on the Géoportail de l’urbanisme or at the mairie.
- The height, ground coverage and siting rules for that zone.
- Requirements shown on the map: reserved site, protected woodland, protected building.
- Neighbouring zones, especially if an AU or U zone borders the garden.
- Hazards, which can add their own rules to the PLU.
Frequently asked questions
Can a house in an N zone be sold normally?
Yes. The classification does not prevent the sale; it limits future works. Check what the rules allow for existing homes.
What do UA, UB or 1AU mean?
They are sub-zones specific to each PLU. The legend of the zoning map and the rules give their meaning in the commune concerned.
Does an AU zone next to the house mean new buildings?
Not necessarily straight away, but that is what the zone is for. The sector’s OAP, if there is one, describes the intended scheme.
Can the zoning change after the purchase?
Yes, when the PLU is revised or amended, after a public inquiry. Ask the mairie whether a procedure is under way.
Sources
- Service-public.fr: building in a farmland zone
- Service-public.fr: planning questions before building
- Géoportail de l’urbanisme
- Urban Planning Code, arts L151-12 and R151-18 to R151-24
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