27 September 2026

Diagnostics when buying a property in France

What is actually examined?

Anyone buying a property in France will usually receive a substantial package of documents before the purchase: the dossier de diagnostic technique, or DDT. Depending on the property, this may contain information about asbestos, lead, electricity, gas, termites, energy performance, natural risks and drainage. For an apartment or another part of a copropriété, this also includes the surface area according to the Loi Carrez.

In principle, the seller must attach the DDT to the promesse de vente or compromis de vente. If no preliminary contract is signed, it is provided with the acte authentique. Which diagnostics are required depends, among other things, on the age and location of the property, the installations present and the type of property.

For Dutch buyers, this can easily lead to a misunderstanding. The word diagnostic makes it sound as though the property has been fully inspected from a technical perspective. This is not the case. Each of the different diagnostics examines a legally defined subject. Together, they do not constitute a general building survey of the property.

A property can therefore have a complete and valid DDT while at the same time having a leaking roof, damp problems, cracking, poor foundations or other structural defects that are not covered by these reports. This distinction is particularly important with older properties.

One dossier, different inspections

There is no single universal technical inspection in France that is the same for every property. The DDT is a collection of separate inspections and statements.

Depending on the situation, the legally regulated components include the constat de risque d'exposition au plomb (CREP), the asbestos inspection, the termite inspection, the gas and electricity diagnostics, the état des risques, the DPE and, where applicable, the audit énergétique, as well as the inspection of an individual wastewater treatment system. The law also provides for a number of more specific information requirements that apply only in certain situations.

The DPE is therefore also part of this dossier. As the energy performance of a property and its implications for buyers have now become an extensive subject in their own right, the DPE was covered in an earlier article in this series.

The other diagnostics each tell you something different about the property.

Asbestos: particularly relevant in older buildings

For buildings for which the building permit was issued before 1 July 1997, an inspection must be carried out upon sale to determine whether certain materials or products contain asbestos.

The presence of asbestos does not automatically mean that a property is unsafe or cannot be sold. Nor is finding asbestos-containing material in older French properties unusual in itself. Its significance depends very much on the material, its condition and where it is located.

For a buyer, this becomes particularly relevant when renovation work is planned. An asbestos-containing material that does not present an immediate problem in its existing condition may, when cut, drilled, removed or demolished, lead to additional safety measures and considerable costs.

A diagnostic amiante should therefore not simply be read as an answer to the question of whether asbestos is present. At least as important is where it is located and what the buyer intends to do with that part of the property.

Lead: particularly in properties dating from before 1949

For properties built before 1 January 1949, a constat de risque d'exposition au plomb, usually referred to as CREP, may be mandatory. This mainly looks at lead-containing paint layers and the condition they are in.

Here too, context is important. Lead-containing paint underneath intact newer layers of paint is different from damaged or flaking paint from which lead-containing dust may be released.

For someone intending to renovate an older property, this information may therefore be more relevant than for someone moving into a recently renovated apartment where no work is planned.

Electricity: not the same as complying with current standards

When residential property is sold, an état de l'installation intérieure d'électricité must be provided if the electrical installation is more than fifteen years old.

This report is sometimes misinterpreted. When a property is sold, an existing installation does not automatically have to comply fully with all the standards that currently apply to a new electrical installation. The diagnostic is primarily concerned with safety risks and lists the anomalies identified.

This also means that a list of irregularities does not necessarily mean that the entire installation must be replaced. Some observations are relatively easy to remedy, while others may indicate an installation that should be examined more closely by an electrician.

Particularly in older villas, where parts of the installation have been added or renewed over the years, it is sensible to look at the contents of the report rather than only at its conclusion.

Gas: also from fifteen years onwards

A similar requirement applies to a fixed gas installation that is more than fifteen years old. The état de l'installation intérieure de gaz examines parts of the installation that are relevant to safety, including pipes, connections, ventilation and connected appliances.

An unfavourable gas diagnostic does not automatically prevent the sale either. It informs the buyer about identified risks. The seriousness of an anomalie then determines whether further investigation or work is advisable or necessary.

Termites: not a theoretical risk on the Côte d'Azur

The état relatif à la présence de termites is mandatory when a property is located in an area designated by the prefecture as a risk area. The termite report has a limited period of validity; when a property is sold, it is in principle valid for six months.

This report deserves particular attention in older properties. Termites can damage wooden elements without this being immediately visible during an ordinary viewing.

At the same time, the scope of the diagnostic must also be understood. A termite inspection is not a complete structural assessment of all the wooden elements of a property. If traces of termites or damage are identified, further specialist investigation may therefore be advisable.

État des risques: not the property, but the location

A very different document is the état des risques. This does not primarily concern the technical condition of the building, but the risks associated with the place in which it is located.

These may include flooding, forest fires, landslides, earthquake risk, technological risks or radon. The information that must be provided depends on the location of the property and the plans and classifications applicable to that area. In designated areas, the état des risques forms part of the DDT.

On the Côte d'Azur, this is by no means a formality. A villa on a hillside, a property near a watercourse or a house on the edge of a wooded area may face very different risks from an apartment in central Nice.

A reference in the état des risques does not automatically mean that the property is dangerous or that damage has occurred there in the past. It means that a particular risk has been identified for that location. For a buyer, the relevant question is then what this means in practical terms for the plot, any renovation plans and the insurability of the property.

It is therefore very much a document that should be read rather than simply ticked off.

Assainissement: connected to the mains sewer or a fosse septique?

For properties outside built-up areas, it is quite common for the house not to be connected to the public sewer system. There may, for example, be a fosse septique or another assainissement non collectif system.

When the property is sold, an inspection report for this installation must be provided where the relevant rules apply. If the installation does not comply at the time of transfer, French regulations require the buyer to have the necessary work carried out within one year after the acte authentique.

Financially, this can be far more significant than the word "diagnostic" might suggest. An outdated, incorrectly sized or improperly installed system can require substantial work.

For a villa with a fosse septique, it is therefore sensible not only to check whether the report is present, but above all to look at its conclusion and any recommended modifications.

Loi Carrez: how many square metres are you actually buying?

When an apartment or another lot de copropriété is sold, the measurement under the Loi Carrez is also of great importance. It determines the superficie de la partie privative: the private surface area of the part of the copropriété being sold.

The legal basis can be found in Article 46 of the French law on copropriété of 10 July 1965. The surface area must be stated in the agreement under which a lot, or part of one, is sold. The rules do not apply to, among other things, cellars, garages and parking spaces, nor to separate lots or parts of lots below the prescribed minimum surface area.

The superficie Loi Carrez is not necessarily the same as the number of square metres experienced as living space during a viewing.

The calculation is based on the floor area of enclosed and covered spaces. The areas occupied by walls, partitions, stairs and stairwells, service shafts, and door and window openings are deducted. Areas where the ceiling height is less than 1.80 metres are not included. Separate lots or fractions of lots smaller than 8 m² are also excluded from the calculation.

This explains why different surface-area figures are sometimes given for the same French property. An apartment may, for example, have a low attic space or other usable area that certainly has value in everyday use, but is not, or not fully, included in the Carrez surface area.

It is therefore sensible for a buyer not only to look at the surface area stated in an advertisement, but also at the official superficie privative Loi Carrez.

The rules also provide important protection for the buyer. If, after the purchase, the actual Carrez surface area proves to be more than 5 per cent smaller than the surface area stated in the deed of sale, the buyer can in principle claim a proportionate reduction in the purchase price. The claim must be brought within one year after the acte authentique. If the actual surface area turns out to be larger, the seller cannot claim an additional purchase price on the basis of these rules.

The Carrez measurement obviously says nothing about the technical quality of those square metres. But when buying an apartment, it does answer a very fundamental question: how much private surface area is actually being purchased from a legal perspective?

Audit énergétique: in addition to the DPE

For certain properties, an audit énergétique is mandatory in addition to the DPE. The audit goes considerably further than simply stating the letter of the energy rating and contains proposals and scenarios for improving the energy performance.

For sales where it is required, the audit énergétique forms part of the information that must be provided to the prospective buyer; Article L271-4 also provides that the audit must be handed to the prospective buyer at the first viewing.

However, an audit énergétique should not be confused with a building survey either. The assessment focuses on the energy performance of the building and possible energy-efficiency improvements.

What happens if a diagnostic identifies a problem?

An important misconception surrounding diagnostics is that a problem identified in a report must automatically be remedied by the seller before the property can be sold. In general, this is not the case.

The French system is focused on providing information to the buyer. Before the purchase, the buyer must be able to see which risks or irregularities have been identified within the subjects covered by the statutory inspections. It must then be assessed what that information means for the particular purchase.

With an old electrical installation, obtaining a quotation from an electrician may be useful. If termites are found, specialist investigation may be necessary. If asbestos is present, a planned renovation may become more expensive and complicated. And in the case of a non-compliant fosse septique, the buyer knows that work will have to be carried out after completion.

The legal consequences are also not the same for every diagnostic. Article L271-4, for example, links the absence of certain valid diagnostics at the time of the acte authentique to consequences for the seller's ability to rely on an exclusion of liability for the relevant hidden defects. The law provides different consequences for other documents.

A DDT should therefore not be read simply as a list of "good" or "bad". It is information that must be assessed in conjunction with the property, the price, the buyer's plans and the purchase agreement.

Diagnostics are not a building survey

For Dutch buyers, this is perhaps the most important distinction of all. A complete DDT does not mean that the property has been approved from a structural or building-technical perspective.

The diagnostiqueur does not automatically assess the quality of the foundations, the roof structure, the cause of cracks or damp problems, the stability of a retaining wall or the quality of previous renovation work. These matters may fall outside the scope of the statutory inspection.

The professionals who carry out the relevant diagnostics must comply with statutory requirements regarding expertise, insurance, independence and impartiality. France also has a public register that can be used to check whether a diagnostiqueur is certified for the relevant field.

But a certified diagnostiqueur immobilier is not therefore a building surveyor who assesses the complete technical condition of the property.

For a relatively recent apartment, the diagnostic dossier may contain much of the directly relevant technical information. For an older villa, a mas, a property with extensions, visible cracking or a house that is to undergo major renovation, additional investigation by an architect, building expert or other specialist may be advisable.

Do not read only the first page

Diagnostics are usually provided together with a large number of other documents. Particularly in the case of a copropriété, the complete dossier can be extensive. It is tempting simply to check whether all the documents are present and then move on to the compromis.

Yet it is often in the pages following the summary that the information relevant to the buyer can be found. Which anomalies have been identified in the electrical or gas installation? Where is any asbestos located? Are there signs of termites? Which risks apply to the plot? What is the condition of the fosse septique? And, in the case of an apartment, what is the official superficie Loi Carrez?

The dates of the reports also deserve attention. The period of validity differs from one diagnostic to another. Article L271-5 provides that if a required document that was still valid at the time of the promesse de vente expires before the acte authentique is signed, a new document must be drawn up and attached to the final deed. An état des risques must also be supplemented or updated at the time of the final transfer if the relevant risk information has changed in the meantime.

Ultimately, the number of pages in the diagnostic dossier says very little. Its value lies in understanding what has actually been established, what this means for the specific property and, just as importantly, what has not been examined.