Mandatory Diagnostics for Commercial Leases: 2026 Guide

Mandatory diagnostics are a major issue when a commercial lease (bail commercial) is entered into. With strengthened legal obligations and responsibilities shared between landlords and tenants, the regulations are constantly changing and call for particular vigilance from commercial property professionals. Failure to understand these obligations can have significant legal and financial consequences for all parties.

Legal framework for diagnostics in commercial leases

Legal foundations

The French Construction and Housing Code, the French Environmental Code and the French Labour Code are the main regulatory sources governing technical diagnostics for commercial leases. Unlike a residential lease, the commercial lease statute allows greater contractual freedom, but does not release the parties from certain mandatory legal obligations.

The ALUR Act of 2014 and its implementing decrees have considerably strengthened diagnostic obligations, particularly in environmental and safety matters. These texts apply to commercial leases under specific rules that need to be mastered.

Responsibilities of the landlord and the tenant

The landlord generally bears the cost of diagnostics relating to the structure of the building and the installations it makes available. The tenant may be held responsible for diagnostics concerning its own fittings or equipment, depending on the contractual provisions.

This allocation of responsibilities must be clearly set out in the lease to avoid any later dispute. The parties may depart from the default rules by specific contractual clauses, within the limits of mandatory public-policy provisions.

Mandatory diagnostics in 2026

Energy performance diagnostic (DPE)

The energy performance diagnostic (DPE) for commercial leases has been an essential element since the 2021 reform. For commercial premises of more than 250 m², the diagnostic must be carried out under the new methodology and provided to the tenant before the lease is signed.

Tertiary buildings are subject to specific energy performance obligations, with staged deadlines up to 2030. The commercial DPE takes these constraints into account and makes it possible to anticipate future energy renovation works.

A DPE is valid for ten years, but an update may be necessary where works substantially change the energy performance of the premises.

Asbestos diagnostic

The asbestos report applies to all buildings for which the building permit was issued before 1 July 1997. This diagnostic is particularly important in commercial leases, given the health risks to employees and customers.

The asbestos diagnostic has several components depending on the use of the building:

• Identification of materials and products containing asbestos
• Assessment of their state of conservation
• Recommendations for management or works

Where asbestos is present, the landlord must inform the tenant and put appropriate protective measures in place. A tenant planning works must also have a pre-works diagnostic carried out. The obligation on the project owner (maître d'ouvrage) before a site starts is set out in our article on asbestos surveys before works.

Lead diagnostic

The lead exposure risk report (constat de risque d'exposition au plomb, CREP) applies to buildings constructed before 1 January 1949. Although less common in commercial matters, this diagnostic may concern certain older premises, particularly in historic city centres.

The presence of lead requires particular precautions during renovation works and may affect the commercial use of the premises, in particular for activities involving contact with the public or food.

Condition of the electrical installation

Electrical installations more than fifteen years old must be the subject of a specific diagnostic. This obligation takes on a particular dimension in commercial leases, where electrical needs are often substantial and specialised.

The electrical diagnostic assesses the installation's compliance with safety standards and identifies potential risks. It must be supplemented by a compliance check for new or renovated installations.

Condition of the gas installation

Like the electrical diagnostic, the report on the condition of the internal gas installation concerns installations more than fifteen years old. This diagnostic is crucial for businesses that use gas (restaurants, craftsmen, etc.).

Anomalies detected must be remedied by compliance works within precise time limits, failing which use of the installation may be prohibited.

Activity-specific diagnostics

Disabled access diagnostic

Establishments open to the public (établissements recevant du public, ERP) have been subject to strengthened accessibility obligations since 2015. The accessibility diagnostic assesses the premises' compliance with the standards in force and determines the works required.

This obligation concerns most businesses and may require costly adaptations. Responsibility for bringing the premises up to standard must be clearly allocated between landlord and tenant in the lease.

Termite diagnostic

In areas delimited by prefectoral order, a termite report may be required. This diagnostic mainly concerns the departments of southern France, but is gradually spreading northwards.

The presence of termites can compromise the structure of the building and require specialist treatment. Informing the tenant is mandatory where infestation is established.

Radon diagnostic

Radon, a naturally occurring radioactive gas, is subject to enhanced monitoring in certain geographical areas. Tertiary buildings located in municipalities classified in zone 3 must be screened.

This relatively recent obligation concerns approximately 7,000 French municipalities and may affect the rental value of the property.

Implementation and sanctions

Practical arrangements

The mandatory diagnostics for commercial leases must be carried out by certified diagnosticians, save for specific exceptions. The certification must be valid and correspond to the type of diagnostic carried out.

The diagnostics must be annexed to the lease or provided to the tenant before signature. Where they are missing or irregular, the tenant may rely on a defect of consent or seek annulment of the lease. On the technical diagnostics file required on a sale, see our article on mandatory diagnostics in property sales.

The period of validity of diagnostics varies according to their nature:

• DPE: 10 years
• Asbestos: unlimited if none is found, 3 years if present
• Lead: 6 years
• Electricity and gas: 6 years
• Termites: 6 months

Consequences of non-compliance

The absence of a diagnostic may lead to several types of sanction:

• Civil liability in the event of damage
• Annulment of the lease for defect of consent
• Criminal penalties for endangering others
• Administrative liability for failure to comply with ERP obligations

The landlord cannot escape liability by a contractual clause excluding statutory guarantees. Case law regularly penalises attempts at abusive exclusion of liability.

Disputes and case law

The courts are increasingly demanding as regards information given to the tenant. The duty to inform extends beyond the mere provision of the diagnostics and includes explaining their practical consequences.

In the event of a dispute, the burden of proof lies on the landlord, who must show that it has met its diagnostic obligations. Breaches may give rise to substantial damages.

Regulatory developments and outlook

New environmental obligations

The Tertiary Decree (Décret tertiaire) sets energy consumption reduction targets for buildings of more than 1,000 m². These obligations come with new diagnostics and periodic energy audits.

The Climate and Resilience Act strengthens energy performance obligations by progressively prohibiting the letting of the most energy-intensive dwellings. Although this measure mainly concerns residential property, an extension to commercial property is under consideration.

Digitalisation of diagnostics

The gradual dematerialisation of diagnostics makes them easier to store and transmit. Digital platforms allow real-time monitoring of the validity of diagnostics and of renewal obligations.

Artificial intelligence and connected devices open new prospects for continuous monitoring of the performance of commercial buildings.

European harmonisation

European directives on the energy performance of buildings strongly influence French regulation. Harmonising diagnostic standards at European level will be a major issue in the years ahead.

Practical recommendations

For landlords

Landlords should anticipate the renewal of diagnostics before they expire and keep an up-to-date register of all technical documents. Building a complete technical file enhances the value of the property portfolio and makes marketing easier.

An overall energy audit of the portfolio makes it possible to optimise investment and anticipate regulatory developments. Putting a multi-year works plan in place secures landlord and tenant relations.

For tenants

The completeness and validity of the diagnostics should be checked before the lease is signed. Assistance from a legal adviser experienced in this area makes it possible to identify the risks and negotiate appropriate clauses.

Assessing the impact of the diagnostics on the business's operations is a key element of the decision on where to locate. The costs of bringing the premises up to standard must be built into the business plan.

Mastering the mandatory diagnostics for commercial leases is a strategic issue for all players in commercial property. The constant evolution of the regulations requires permanent legal monitoring and anticipation of future constraints. Given the growing complexity of these obligations, support from a property law professional is essential to secure your projects and optimise your investments.