Real Estate Technical Diagnostic File (DDT): The Complete Guide for Selling in France in 2026

Selling a property in 2026 requires compiling a complete and compliant Technical Diagnostic File (DDT). This file gathers all mandatory real estate diagnostics designed to protect the buyer and secure your transaction. This guide walks you step by step through what the DDT is, which diagnostics it includes, their validity periods, typical costs, and best practices for property sellers.

What is the Technical Diagnostic File (DDT) in French Real Estate?

Definition and Purpose of the DDT in France

The Technical Diagnostic File (DDT) is a set of documents grouping together all mandatory property diagnostics intended to inform the buyer or tenant about the actual condition of the property. It is essentially the property’s technical inspection report, similar to the one carried out for a car before purchase.

The purpose of the DDT is twofold: to protect future occupants by informing them of potential health and safety risks, and to assess the property’s energy performance. It enables buyers to make an informed decision by identifying elements of the property that may require work or present hazards.

These documents cover various aspects such as the presence of hazardous materials (asbestos, lead), the condition of installations (electricity, gas), environmental risks, and the energy consumption of the property.

French Legal Framework: Article L271-4 of the Construction and Housing Code and the Alur Law

The legal basis of the DDT lies in Article L271-4 of the French Construction and Housing Code. This text specifies the list of mandatory diagnostics to be provided during a real estate transaction, their application conditions, and exemptions depending on the type, age, or location of the property.

The 2014 Alur law strengthened obligations related to co-ownership, requiring additional documents such as the building maintenance logbook and the global technical diagnosis (DTG) for co-ownerships over 10 years old. These measures aim to improve transparency and buyer protection.

In 2026, several regulatory updates apply. The energy performance diagnosis (DPE) calculation method has been updated as of January 1, 2026, to better reflect actual energy performance, particularly for electrically heated homes. Additionally, collective DPE is gradually becoming mandatory for co-ownerships depending on their size, in line with the Climate and Resilience law.

Who Must Provide the DDT and When?

The seller is legally required to compile and provide the complete DDT. It must be attached to the preliminary sale agreement or promise to sell, and no later than the signing of the final deed before a notary.

In public sales, the DDT is included in the specifications and made available to potential buyers before bidding. The seller remains responsible for the completeness and validity of the diagnostics, even when commissioning a certified professional.

It is strongly recommended to prepare the DDT at the valuation stage, before listing the property. This helps avoid delays and reassures buyers from the first viewing.

What Property Diagnostics Are Mandatory for a Sale in France?

When selling property in 2026, you must compile a complete DDT including several mandatory diagnostics. Each serves a specific purpose: informing the buyer, ensuring safety, and complying with regulations.

Energy Performance Diagnosis (DPE)

The DPE evaluates energy consumption and greenhouse gas emissions, rating the property from A (very efficient) to G (very energy-intensive). It is mandatory for all sales.

Since January 1, 2026, the calculation method has evolved, particularly benefiting electrically heated properties. The DPE is valid for 10 years.

Asbestos Diagnosis

Required for properties with building permits issued before July 1, 1997, this diagnosis identifies the presence of asbestos materials.

If no asbestos is found, the report has unlimited validity. If asbestos is present, its condition and required measures must be specified.

Lead Exposure Risk Report (CREP)

Applicable to properties built before January 1, 1949, this report measures lead levels in coatings to prevent health risks.

If no lead is found, validity is unlimited. If lead exceeds thresholds, validity is one year.

Electrical and Gas Diagnostics

Required if installations are over 15 years old, these diagnostics ensure safety and compliance.

Each is valid for 3 years for a sale.

Termite Diagnosis

Mandatory in designated risk areas, this report must be issued within 6 months before the sale.

Environmental Risks and Pollution Report (ERP) and Noise Diagnosis

The ERP informs about natural, technological, and environmental risks. It must be less than 6 months old.

The noise diagnosis applies to properties near airports.

Carrez Law Measurement and Non-Collective Sanitation Diagnosis

The Carrez law measurement is mandatory for co-ownership units over 8 m².

The sanitation diagnosis applies to homes not connected to public sewage systems and is valid for 3 years.

DDT for a House

For a house, the DDT includes all base diagnostics plus specific checks such as non-collective sanitation and termite diagnosis where applicable.

DDT for an Apartment in Co-ownership

For apartments, specific requirements include:

Mandatory Documents Attached to the Preliminary Sale Agreement

The DDT must be attached to the preliminary agreement and final deed. All diagnostics must be valid at signing.

Is the DDT Also Mandatory for Rentals in French Real Estate?

Yes, the DDT is also required for rental properties.

Diagnostics Required for Rentals

For rentals, required diagnostics include:

The asbestos report must be available but not attached.

Differences Between Sales and Rental DDT

The DDT for sales includes more diagnostics than for rentals, reflecting the higher level of buyer protection required.

Validity Periods and Costs of Diagnostics

Summary Table of Validity

Average Cost of a DDT in 2026

A complete DDT typically costs between €290 and €700 depending on the property.

Bundled packages can reduce costs by 20% to 50%.

Who Carries Out the Diagnostics?

Requirement for a Certified Diagnostician

Diagnostics must be carried out by a certified professional accredited by Cofrac.

They must also have professional liability insurance and be independent from all parties.

How to Choose a Reliable Professional

Consequences of an Incomplete or Missing DDT

Penalties for the Seller

Buyer Remedies

Best Practices for Sellers

Anticipate Diagnostics

Prepare the DDT early to avoid delays and reassure buyers.

Common Mistakes to Avoid

Capifrance Supports Your Property Sale

Capifrance advisors help you prepare a complete DDT, recommend certified professionals, and ensure compliance.

FAQ

Is the DDT Mandatory?

Yes, it is legally required for all property sales and rentals in France.

How Much Does a DDT Cost?

Between €300 and €700 depending on the property.

What is the Difference Between DPE and DDT?

The DPE is one component of the DDT, which includes all diagnostics.

Can You Sell Without Diagnostics?

No, it is illegal and exposes the seller to serious consequences.

What Diagnostics Are Required for an Apartment?

Author :

Frédéric Rémy – Director of Commercial Performance
A real estate professional for several years within the Capifrance network, I would like to share with you some essential advice to help you succeed in your real estate project with the support of our advisors.