French prior declarations with Claude: organize existing and proposed work
French prior declarations: 5/20/40 m² thresholds, the current CERFA 16702*03, the 1-month timeline and tacit non-opposition.
By Educasium
Prepare supporting documents for a French DP with Claude →
A client wants to replace two windows in their house with a different colour, without changing their dimensions. They think a simple before/after photo will be enough to inform the town hall. Their architect knows a prior declaration is probably needed, but hesitates over which document to attach: a full façade drawing seems disproportionate for two windows, while a plain written description risks being judged insufficient by the reviewing authority.
The déclaration préalable (DP, prior declaration) is the lighter regime of French planning law: it applies to works that, without being exempt from any formality, do not justify the heavier review of a building permit. Its reduced formality does not, however, excuse rigor: a description poorly matched to the graphic documents actually required exposes the application to a request for further documents, or even an objection.
This article details the thresholds that trigger a prior declaration rather than a building permit or no formality at all, the instruction timeline and the tacit non-opposition mechanism, the currently applicable CERFA form, and the method for preparing supporting documents without ever confusing a file name with a document's regulatory nature.
Summary
- What a prior declaration covers, and what it does not
- The area thresholds that trigger a DP rather than a permit
- The instruction timeline and tacit non-opposition
- Preparing the DP documents step by step
- When a DP is not enough
- Training to make prior declarations more reliable
- Frequently asked questions
What a prior declaration covers, and what it does not
A prior declaration covers works creating a limited floor area or ground coverage, changes to external appearance — façade, roof, fencing — or certain changes of use unaccompanied by any modification to load-bearing structure or façade. It applies neither to routine maintenance works, generally exempt from any formality, nor to projects whose area or nature exceeds the thresholds that impose a building permit.
Why the applicable regime depends on facts an AI cannot verify
The exact regime applicable to a given project depends on the precise area created, whether the municipality has a local urban plan, and the possible classification of the sector — protected or not. A document-generation tool knows none of these elements on its own: it can only work from what the architect supplies, with the risk that a rounded area or an assumed zone classification, unverified, wrongly shifts an application that actually required a building permit towards a simple prior declaration.
The area thresholds that trigger a DP rather than a permit
Article R421-17 of the Code de l'urbanisme sets the following thresholds for works creating area on an existing building.
| Situation | Area created | Applicable regime |
|---|---|---|
| All zones | 5 m² or less of floor area or ground coverage | In principle no formality, subject to the other cases covered by the same article |
| Municipality with no PLU or equivalent planning document | More than 5 m² and up to 20 m² | Prior declaration |
| Municipality with a PLU, urban zone | More than 5 m² and up to 40 m² | Prior declaration |
| All zones | Beyond these thresholds, or if the total later exceeds 150 m² of floor area | Building permit |
Beyond the mere creation of area, a prior declaration is also required for works that change the external appearance of an existing building — replacing windows with a colour change, resurfacing that alters appearance, installing a fence where the municipality requires it — whatever the area involved, as soon as those works do not amount to routine maintenance exempt from formality.
The instruction timeline and tacit non-opposition
The instruction timeline for a prior declaration is markedly shorter than for a building permit, according to Service Public.
| Situation | Instruction timeline | Effect of the administration's silence |
|---|---|---|
| Ordinary zone | 1 month from filing the complete application | Tacit non-opposition: the works may start |
| Protected sector | 2 months from filing the complete application | Tacit non-opposition: the works may start |
No response from the administration within these timelines amounts to non-opposition to the declared works, which allows them to start — but does not excuse keeping proof of filing and of the time elapsed. The applicant may, if they wish, request a certificate of non-opposition from the town hall, a document useful in particular when later reselling the property, to prove the regularity of the works carried out.
At the time this article was checked, the CERFA form applicable to a prior declaration for construction or works not subject to a building permit carries reference 16702*03; this reference has replaced the older forms 13703 and 13404, and must be verified on service-public.gouv.fr on the filing date rather than reused from a previous application.
Preparing the DP documents step by step
Step 1: Describe what exists and what changes, separately. A description that mixes the existing and proposed states makes comparison harder for the reviewing authority; the two states must be presented side by side, item by item.
Step 2: Match each described element to a reference on the graphic documents. For a window change, the description must identify the window concerned by its location, not by a general phrase such as "the façade joinery".
Step 3: Check the procedure suited to the project and the sector's specific features. A protected sector — the surroundings of a historic monument, a remarkable heritage site — may require additional documents or extend the instruction timeline, to be checked with the town hall before filing.
Step 4: Never confuse a file name with a document's regulatory nature. A document named "DP4 note" by a tool or a generic template has value only if its content actually matches the document required by the official list currently in force for that type of project.
Step 5: File the complete application and keep proof of filing and of the date. It is that date which starts the instruction timeline and, if the administration stays silent, the tacit non-opposition period.
When a DP is not enough
A properly prepared prior declaration does not cover every situation. A project whose area, even modest at first, takes the building's total area beyond the 150 m² threshold falls under a building permit with mandatory recourse to an architect, whatever the extension's own area. A persistent doubt over the sector's classification — protected or not, covered by a PLU or not — must be resolved with the town hall before filing, rather than assumed from a neighbouring project handled differently. A written description prepared with AI assistance never replaces a drawing required by the official list: when the reviewing authority asks for a façade drawing, a narrative cannot substitute for it, however precise.
Training to make prior declarations more reliable
A checklist template is not enough if the thresholds and the sector's specific features are not re-checked for every application. For an architect practising as a self-employed professional (NAF code 7111Z in France), the FIFPL fund covers part of the cost of Qualiopi-certified training under 2026 criteria set at €300 per day and €900 per year, with e-learning capped at 50% of the daily rate. This funding must be arranged before training starts, not after.
Frequently asked questions
Does simply changing the colour of windows require a prior declaration?
In most cases yes, as soon as that change alters the building's external appearance, regardless of any area created. The exact rule, however, depends on local provisions and any classification of the sector, to be checked with the town hall before treating the works as exempt from formality. This upfront check avoids the frequent case where seemingly minor works, started without any formality, must be regularized afterwards at the reviewing authority's request.
What happens if the administration does not respond within the instruction timeline?
No response within the applicable timeline — one month in an ordinary zone, two months in a protected sector — amounts to tacit non-opposition to the declared works, which in principle allows them to start. It nonetheless remains useful to keep proof of filing and, if needed, to request a certificate of non-opposition from the town hall for a formal document. That certificate proves especially useful years after the works, when reselling the property requires proving their regularity without an express administrative decision to rely on.
Does the CERFA form used last year still apply?
Not necessarily: prior-declaration forms have been updated, with the old CERFA 13703 replaced by CERFA 16702 for constructions and works not subject to a building permit. The reference in force must be checked on service-public.gouv.fr on the filing date, rather than reusing an archived form. An application filed with an outdated form risks a request for additional documents that pushes back the start of the instruction timeline by the same amount.
Can a written note replace a façade drawing requested by the reviewing authority?
No: when the official list requires a façade drawing or any other graphic document, a written description, however detailed, cannot substitute for it. The name a generation tool gives a file does not change the regulatory nature of the document expected by the administration. Confusing the two amounts, in practice, to filing an incomplete application: the reviewing authority will request the missing graphic document before resuming review.
Can a prior declaration turn into a building permit during review?
This does not happen automatically: if the reviewing authority considers that the declared project actually requires a building permit, it generally notifies the applicant that a new application must be filed under that procedure. That is one more reason to check the applicable thresholds before the initial filing, rather than letting the reviewing authority settle the question in the architect's place. This switch resets the instruction timeline to zero under the new regime, which can noticeably delay the start of works compared with an application correctly classified from the outset.
A reliable prior-declaration application rests on three elements that do not change from one project to the next: a clear distinction between the existing and proposed states, a checked match between each description and its graphic document, and confirmation of the applicable regime with the town hall rather than an automatic assumption. Once that foundation is in place, it is exactly what the DP document generator organizes, never substituting for the competent service's review.
When a project exceeds the prior-declaration thresholds, our method for organizing a building-permit file details the documents expected for that fuller regime.
Training 100% fundable via OPCO/FIFPL. Qualiopi-certified programme. To structure your planning applications and contractual documents with AI as part of our AI for architectural management training, contact Educasium and specify your status (employee, self-employed, business owner) and your goal.