Garden Cabins in France: Déclaration Préalable, Permits and Taxes Explained

France is one of the most rewarding places in Europe to put up a wooden garden building. Land is more generous than in much of the continent, the climate suits timber well, and — contrary to its reputation for paperwork — the national rules for garden cabins are actually refreshingly clear. Three surface thresholds decide almost everything, and once you know them, you know exactly which procedure applies to your project.

This guide walks through those thresholds, the déclaration préalable de travaux, the permis de construire, the height and boundary rules set by your local PLU, and the one cost that surprises most buyers: the taxe d'aménagement. It is written for anyone planning a log cabin, garden office, summerhouse or wooden annexe on a French property.

The Three Surface Thresholds That Decide Everything

French planning law (Articles R421-2, R421-9 and R421-1 of the code de l'urbanisme) sorts new detached garden buildings up to 12 m high into three bands based on surface. The area that counts is the larger of the surface de plancher (internal floor area) or the emprise au sol (the footprint the building projects onto the ground, including roof overhangs supported by posts).

• Up to 5 m²: no formality is required in the general case. You can install the building without asking anyone — though local PLU rules on placement and appearance still apply.
• More than 5 m², up to 20 m²: a déclaration préalable de travaux (prior declaration of works) must be filed with your mairie before work begins.
• More than 20 m²: a permis de construire (building permit) is required.

These bands apply across France, but they are the floor, not the ceiling: protected areas and local plans can tighten them, which is why the last step before ordering should always be a conversation with your mairie's service urbanisme.

Under 5 m²: No Formalities — With Two Caveats

A small tool store or bike shelter under 5 m² needs no application in most of France. There are two important exceptions. First, in protected sectors — in the abords (surroundings) of a monument historique, in a site patrimonial remarquable, or in a site classé or one pending classification — a déclaration préalable is required even below 5 m². Second, the PLU still governs where on the plot you may place the structure and what it may look like, so "no formality" never means "no rules".

The good news: buildings of 5 m² or less are also outside the scope of the taxe d'aménagement, so a genuinely small shed carries no tax either.

5 to 20 m²: The Déclaration Préalable de Travaux

This is the band most garden cabins fall into, and the procedure is straightforward. You file Cerfa form no. 13703 — on paper at the mairie or through your commune's online planning portal — with a site plan, a simple elevation drawing and a short description of materials and colours. A compact model such as the Kemi 4 × 3 m, with a 12 m² footprint, sits squarely in this category.

The standard review period is one month, extended to two months in protected sectors where the Architecte des Bâtiments de France must give an opinion. If the mairie does not respond within the deadline, silence generally counts as acceptance (a décision de non-opposition tacite) — except in a few protected cases, such as a site classé, where silence means refusal. Once accepted, you must display the authorisation on a panel visible from the street for the duration of the works.

A manufacturer's technical drawings make this file far easier to assemble. Satus Baltic can prepare dimensioned technical drawings for any model — exactly what the declaration asks for.

Above 20 m²: The Permis de Construire

Cross the 20 m² line and you move into building-permit territory. The application is more substantial — fuller plans, sections, and a description of how the project fits its surroundings — and the standard review period is two months for a house or its annexes (three months for other projects), plus one month in protected sectors. A generous garden house like the Brenzo 5.95 × 5.95 m, at roughly 35 m², needs a permis de construire everywhere in France.

Two further points matter at this scale. If the floor area concerned exceeds 150 m² — for an extension, the total surface de plancher of the building after works — an architect must draw up the plans. And if the cabin will be lived in — a guest annexe or year-round dwelling — it must also meet habitability and, in many cases, energy-performance requirements, so raise this explicitly with the mairie at the outset.

What About the 40 m² Rule in Urban Zones?

You may have read that in zones urbaines covered by a PLU, the déclaration préalable stretches up to 40 m². That is true — but only for extensions attached to an existing building. A detached garden cabin is a construction nouvelle in the eyes of the code de l'urbanisme, and for new detached buildings the permit threshold stays at 20 m² even in urban PLU zones. Even for an extension, the 20–40 m² band still needs a permis de construire if it takes the total floor area or footprint of the building above 150 m². If you want a larger building under the lighter procedure, attaching it to the house as an extension can be a legitimate route — but that is precisely the kind of question to settle with the service urbanisme before you order.

Height Rules, Boundaries and Your Local PLU

Nationally, the 5 m² and 20 m² bands only apply to buildings up to 12 metres high: above 12 m, a building of more than 5 m² needs a permis de construire, and even a structure of 5 m² or less needs a déclaration préalable — rarely relevant for a garden building. What matters in practice is your commune's Plan Local d'Urbanisme (or PLUi), which commonly does three things:

• Caps annexe height — many municipalities limit garden buildings to around 2.5 to 3 m at the ridge or eaves.
• Sets boundary distances — a typical rule allows building either directly on the plot boundary or at a minimum setback, commonly 3 m, but the exact figure varies commune by commune.
• Regulates appearance — roof colour, cladding materials and finishes can all be prescribed, especially in village centres and heritage zones.

Every PLU is public: ask at the mairie or consult the national Géoportail de l'urbanisme. Because Satus Baltic builds every model to order, adjusting ridge height, roof type (bituminous shingles or metal sheets) or wall finish to satisfy a PLU is part of the normal quoting process rather than an expensive exception.

The Taxe d'Aménagement on Garden Buildings

France levies a one-off development tax on new buildings that are over 5 m², enclosed and covered, with a ceiling height of more than 1.80 m — which is why it is nicknamed the "taxe abri de jardin". It is calculated as: taxable surface × a national flat value per m² × the local rates.

For 2026 the flat value is €892 per m² outside Île-de-France and €1,011 per m² within it — down from €930 and €1,054 in 2025. On top of that, communes apply a rate of 1% to 5% (exceptionally up to 20% in specific sectors) and departments up to 2.5% (and, in Île-de-France, the region up to 1%). As a worked example, a 12 m² cabin outside Île-de-France in a commune charging 3% plus a 1.5% departmental share comes to roughly €480, paid once.

Three practical notes. Communes may vote a full or partial exemption for garden sheds of 20 m² or less that go through a déclaration préalable — worth asking about, as many do. You declare the completed building within 90 days of completion via the "Gérer mes biens immobiliers" service in your account on impots.gouv.fr. And amounts up to €1,500 are paid in a single instalment, larger amounts in two.

What Happens If You Skip the Paperwork

It is tempting to treat a wooden building as temporary and skip the formalities. Don't. An unauthorised structure exposes you to a fine of at least €1,200 and up to €6,000 per m² of floor area built (Article L480-4 of the code de l'urbanisme), a possible demolition order at your expense, insurance complications after any loss, and awkward questions when you sell the property — notaries now routinely check that outbuildings were declared. The déclaration préalable costs nothing to file; the risk asymmetry is entirely one-sided.

Your Pre-Order Checklist

• Measure honestly: calculate both surface de plancher and emprise au sol, and use the larger figure.
• Check whether your plot sits in a protected sector — the mairie can tell you in minutes.
• Read the PLU rules for your zone: height caps, setbacks, materials and colours.
• Budget for the taxe d'aménagement if the building exceeds 5 m² with a ceiling height over 1.80 m — and ask whether your commune exempts sheds under 20 m².
• File the déclaration préalable or permis application and wait for approval before ordering assembly.
• Ask your manufacturer for dimensioned technical drawings to attach to the file.

Choosing a Cabin That Fits French Rules — and the French Climate

Once the paperwork is mapped out, choose the building for the use, not just the size band. A 28 or 44 mm wall suits storage and summer use; a garden office or guest annexe used through a continental French winter deserves 58 or 70 mm, or a double-wall 44+44 / 70+70 mm construction with an insulated cavity. Our guide to choosing the right wall thickness covers how to match specification to climate and use.

Satus Baltic has manufactured bespoke log cabins and wooden houses from FSC-certified timber since 2011 and delivers across Europe, France included. Every one of the 34 standard models can be resized or reconfigured — useful when a PLU height cap or a 20 m² threshold argues for a slightly different footprint than the catalogue version.

A necessary disclaimer: planning and tax rules in France differ from commune to commune and change over time. This article reflects the national framework as of 2026 and is general information, not legal advice. Always confirm the rules for your specific plot with your mairie's service urbanisme before ordering.

Ready to plan your project? Browse the full catalogue to find a model that fits your surface band, or request a personalised quote — every quote is prepared by hand within one business day, with the technical drawings your déclaration préalable will need.

Sources

1. Service-Public.fr — Quelle autorisation d'urbanisme déposer pour installer un abri de jardin ?
2. Service-Public.fr — Déclaration préalable de travaux (DP)
3. Service-Public.fr — Permis de construire
4. Service-Public.fr — Taxe d'aménagement
5. Service-Public.fr — Taxe d'aménagement : quels montants en 2025 ?
6. Légifrance — Code de l'urbanisme, constructions nouvelles (Articles R421-1 to R421-12)
7. Légifrance — Code de l'urbanisme, Article R421-9
8. Légifrance — Code de l'urbanisme, Article R421-14
9. Légifrance — Code de l'urbanisme, Article L480-4

Rules checked against these sources on 24 September 2026.