Change of Use of a Dwelling: Prior Authorisation, Condition of Validity of the Lease

You bought a flat in Millau, in the historic quarter, with the intention of setting up your architecture practice there. The notary told you it was possible, that "everyone does it". So you sign a commercial lease with the tenant, without asking any questions. But what happens if the authorities discover that this dwelling, classified as "residential", is actually being used for a professional activity? The answer is simple: the lease can be annulled, and you risk losing your rent.

This is exactly what the Cour de cassation ruled in a judgment of 7 July 2004 (No. 03-11.427). It reminds us of a fundamental rule: the administrative authorisation provided for in Article L. 631-7 of the Code de la construction et de l'habitation (CCH) – i.e. the permission given by the town hall to change the use of a dwelling into professional premises – must be obtained before the lease is signed. Not after, not during. Before.

This decision, handed down in a case between a landlord and his tenant concerning the fixing of rent, has concrete consequences for all owners who let dwellings for mixed use. For without this authorisation, not only can the rent not be set by reference to similar dwellings, but the lease itself is fragile. So, how can you avoid this trap? Follow the guide.

The facts: a story that happens every day

Mr and Mrs Y., owners of a flat in Rodez, grant a lease of a dwelling for residential use to Mr Z., who carries on a liberal profession. The lease provides that the tenant may use the dwelling both for living and for working. This is what is known as a "mixed lease": residential and professional use.

A few years later, the lease comes up for renewal. The landlord proposes a new rent, significantly higher, based on rents charged in the neighbourhood for similar dwellings, including those used for mixed use. The tenant contests this: according to him, these references are not valid because the mixed-use dwellings cited had not obtained the administrative authorisation for change of use. In other words, they were in an irregular situation.

The landlord retorts that the tenant himself uses the dwelling for professional purposes, and that he cannot complain about the lack of authorisation since he benefits from it. But the tenant insists: the authorisation must be applied for by the landlord, not by him. The case is brought before the cour d'appel de Montpellier, which rules in favour of the tenant. The landlord appeals to the Cour de cassation.

The reasoning of the court — broken down

The Cour de cassation, in its judgment of 7 July 2004, dismisses the landlord's appeal. It relies on two fundamental texts: article L. 631-7 of the Code de la construction et de l'habitation (which prohibits changing the use of a dwelling without authorisation) and article 17 c) of the law of 6 July 1989 (which sets the rules for fixing rent in residential leases).

The reasoning is clear: to fix the rent of a renewed lease, the judge must refer to rents of comparable dwellings. But if those reference dwellings are themselves used for mixed use without authorisation, they cannot serve as a basis. Why? Because the administrative authorisation is a condition of the legality of the occupation. A dwelling occupied without authorisation is in breach of the law, and the rent charged in such a dwelling cannot be considered a regular market rent.

The Court specifies that the authorisation must be obtained by the owner prior to the signing of the lease. It does not matter that the tenant was aware of the lack of authorisation or that he derives benefit from it. It is an obligation that rests solely on the owner. In this case, the cour d'appel had found that the references presented by the landlord concerned mixed-use dwellings without authorisation, and it had rightly deduced that they could not be taken into account.

This decision is not a reversal: it confirms a consistent line of authority of the Cour de cassation, already expressed in a judgment of 6 March 1990 (No. 88-13.142). But it clarifies it by applying it to the fixing of rent, which makes it a valuable tool for tenants contesting an excessive increase.

What this means for you — practically

For the landlord: If you let a dwelling for mixed use (residential + professional), you must obtain the authorisation from the town hall before signing the lease. Without this, you risk being unable to justify your rent by reference to similar dwellings. Worse: the tenant could seek annulment of the lease for lack of authorisation. Concrete example: in Espalion, a landlord lets a flat to a lawyer for €800 per month. At renewal, he wishes to increase it to €1,000, based on rents of mixed-use dwellings in the town centre. If those dwellings have no authorisation, the judge may reject the increase and maintain the rent at €800.

For the tenant: You can contest a rent increase if your landlord relies on irregular mixed-use dwellings. You can also require the landlord to regularise the situation. But beware: if you carry on a professional activity without authorisation, you are also in breach of the law vis-à-vis the authorities. It is therefore better to ask the landlord to take the necessary steps, or to inquire yourself at the town hall.

For the purchaser: Before buying a dwelling already let for mixed use, check that the authorisation has been obtained. Ask to see the municipal order. Without it, you could inherit a dispute.

Four tips to avoid this type of dispute

• Before signing a mixed lease, contact the town hall. Ask whether the dwelling is in a regulated change-of-use zone (often large cities or high-pressure areas). If so, submit an application for authorisation. Allow 2 to 4 months for processing.
• Have the permitted use of the premises recorded in the lease. The contract should specify whether the use is exclusively residential, professional, or mixed. This avoids later disputes.
• Keep the administrative authorisation safe. In the event of an inspection or dispute, you will need to produce it. If you have lost it, ask the town hall for a copy.
• At lease renewal, do not rely on suspect dwellings. Ensure that the references you cite relate to dwellings in a regular situation. A simple phone call to the town hall can save you a lawsuit.

Further: related case law and developments

The Cour de cassation reaffirmed this principle in several subsequent judgments. For example, in a judgment of 24 September 2008 (No. 07-16.542), it held that the absence of authorisation for change of use rendered the lease void, and that the tenant could demand restitution of the rents paid. This is a radical consequence, but logical: without authorisation, the occupation is unlawful.

In another judgment of 12 March 2014 (No. 12-28.547), the Court specified that authorisation must be obtained for each change of use, even if the previous owner had already obtained it. In other words, the authorisation is attached to the property, but if the property changes its use (for example, from purely residential to mixed), a new authorisation is necessary.

The trend is therefore towards strictness: the courts protect social housing and the balance of the rental market. Landlords must be particularly vigilant in high-pressure areas, such as Paris, Lyon, or even certain towns in Occitanie like Montpellier or Toulouse.

Key points to remember

FAQ:

• Can I let my flat to a professional without authorisation? No, if you change the use from residential to professional, you must obtain the authorisation from the town hall before signing the lease.
• What does the landlord risk if he has no authorisation? The tenant may contest the rent, seek annulment of the lease, and even demand restitution of the rents. The authorities may also impose a fine.
• Can the tenant apply for the authorisation on his behalf? No, the authorisation must be applied for by the landlord. The tenant cannot apply for it himself.
• How can I tell if a dwelling is in a regular situation? Go to the town hall or consult the local urban plan. You can also ask the landlord to provide you with the authorisation order.
• Is a mixed lease signed without authorisation automatically void? Yes, it can be declared void by a judge. But as long as no challenge is raised, it produces its effects. It is therefore preferable to regularise.

Are you in a similar situation? A first 30-minute consultation with Maître Zakine (€45) can save you months of proceedings — and often much more. Book an appointment →