An erroneous property diagnostic can be costly, both for the seller, whose liability may be engaged, and for the buyer, who discovers a defect after signing. Since the reform of the DPE (energy performance diagnostic) that came into force on 1 July 2021, this document is no longer merely informative: it has become legally enforceable and can serve as the basis for legal action. Undetected asbestos, termites left unmentioned, overlooked lead or an inconsistent DPE: several situations give grounds for a challenge, provided you know the rules and the time limits. This article reviews the cases in which challenging a property diagnostic is possible, the procedure to follow and the remedies available against the diagnostician or the seller.
In summary
- The DPE is enforceable since 1 July 2021: an error can engage the diagnostician's liability and give rise to compensation.
- An erroneous or incomplete asbestos, lead or termite diagnostic makes it possible to take action against the diagnostician, separately from any action against the seller for hidden defects.
- The procedure generally involves a second-opinion diagnostic, a formal notice, then referral to the court if no amicable settlement is reached.
- Time limits vary depending on the legal basis relied upon: up to five years for a DPE error, two years from the discovery of the defect for the other diagnostics.
Mandatory property diagnostics and their role in the sale
In a sale, the seller must provide a technical diagnostic file (DDT) bringing together several documents: the DPE, the asbestos diagnostic, the lead exposure risk assessment, the report on the presence of termites in the areas concerned, and the electricity and gas diagnostics, among others. These property diagnostics inform the buyer about the actual condition of the property before they commit. They are appended to the preliminary sales agreement and then to the notarised deed of sale (acte authentique), which gives them contractual value. A defect, omission or error in any of these documents can therefore have significant legal consequences, both for the professional who produced them and for the seller who passed them on.
A file that engages several parties' liability
The diagnostician, as a certified professional, engages their professional civil liability in the event of an error or negligence in their report. The seller, for their part, remains bound by a duty of good faith: if they were aware of a defect not revealed by the diagnostic, their liability may also be sought on the basis of hidden defects.
Why the reliability of diagnostics is decisive
A reliable report determines the purchase decision, the negotiated price and, for the DPE, the property's energy rating, which now strongly influences its market value. Before committing, it remains useful to compare the property with other similar properties via the property listings available on the market.
On what legal grounds can a property diagnostic be challenged?
Challenging a diagnostic cannot be improvised: it must rely on a specific legal basis. Two approaches coexist depending on the type of diagnostic concerned, and they do not offer the same guarantees to the buyer or seller wishing to take action.
The enforceability of the DPE since 2021
Before the reform, the DPE had only informative value: an error could give rise only to limited compensation, based on a mere "loss of opportunity" to negotiate the price. Since 1 July 2021, the DPE has been fully enforceable. Recent case law has confirmed this change, considering that the provisions relating to its indicative nature had been repealed, and that the loss resulting from an error is now measured by the costs necessary to bring the property into line with the reality of its energy performance.
The diagnostician's fault and duty to advise
For the other diagnostics (asbestos, lead, termites), a challenge rests on demonstrating a fault on the part of the diagnostician: incomplete inspection, failure to follow the required methodology, failure to check at-risk areas. The courts point out that the diagnostician is bound by an enhanced obligation of means: they must systematically search for materials likely to contain the substance in question and cannot rely solely on the seller's statements.
Situations in which a diagnostic can be challenged
In practice, several scenarios come up most frequently before the courts and mediation bodies. Identifying them makes it possible to quickly determine whether an action has a chance of succeeding.
Erroneous or inconsistent DPE
An energy rating that is clearly at odds with actual electricity or gas bills, with the characteristics of the building (insulation, windows and doors, heating system) or with a previous diagnostic report is a strong indication of an error. This is particularly the case where the DPE was carried out without a full inspection of the property or on the basis of incorrect information provided by the seller.
Undetected asbestos, lead and termites
Where the buyer discovers after the sale the presence of asbestos, lead or termites that should have been reported in the diagnostic report, they may hold the diagnostician liable for breach of their professional obligations. This action is independent of any action that might be brought against the seller: in January 2025, the Cour de cassation clarified that the harm resulting from an erroneous diagnostic report concerning termites, asbestos or lead is not limited to a loss of opportunity, but gives entitlement to full compensation for the defects found.
The procedure for challenging an erroneous property diagnostic report
Challenging a diagnostic report generally follows a series of steps, from an amicable approach to legal action if necessary. Following this order makes it easier to build the case file and increases the chances of obtaining prompt compensation.
The second-opinion diagnostic and the formal notice
The first step is to have a second diagnostic carried out by a different certified professional, in order to establish the error objectively. This document, together with the invoices and any supporting evidence (advertisement, deed of sale, works quotes), serves as the basis for a formal notice (mise en demeure) sent to the original diagnostician, inviting them to compensate the harm amicably.
Bringing the matter before the court
In the absence of a response or a satisfactory proposal, it is possible to refer the matter to the diagnostician's certification body and then, if the dispute persists, to the competent tribunal judiciaire. The judge will assess the professional's fault, the causal link with the harm and the amount of compensation, which is generally covered by the diagnostician's professional liability insurance.
Who is liable: the diagnostician, the seller or both
The question of liability is central, as it determines who must compensate the buyer and on what basis to bring an action. The diagnostician and the seller may both be held liable at the same time, but for different reasons.
The diagnostician's liability and insurance
A certified diagnostician is required to hold professional liability insurance. In principle, it is this insurance that compensates the harm caused by a diagnostic error, provided that professional fault is established. It is important to note that this liability is assessed independently of the seller's good or bad faith.
The seller's liability for hidden defects
The seller, for their part, remains liable for hidden defects (vices cachés) that they knew about and did not disclose, even if the diagnostic report did not mention them. However, case law reiterates that a defect that is merely alleged, that was visible during viewings or that is mentioned in the diagnostic report cannot constitute a hidden defect, particularly if the buyer made no comment at the time of the viewing of the property.
What time limits apply for taking action
Limitation periods differ depending on the basis of the action, which makes it essential to react quickly once the problem is discovered.
Limitation period applicable to the DPE
An action for liability against the diagnostician is subject to a five-year limitation period, running from the day on which the error became known, or should have become known, to the buyer or the seller.
Limitation period for asbestos, lead and termites
For the other diagnostics, the period generally applied by the courts is two years from the discovery of the defect. After this period, the action is inadmissible, regardless of the seriousness of the error found.
What compensation can be expected in the case of an erroneous diagnostic report
The amount of compensation depends directly on the basis relied upon and the nature of the harm demonstrated. This assessment always depends on the specific case and requires precise supporting documents.
Full compensation for the harm suffered
For the DPE (energy performance diagnostic) as for asbestos, lead or termites, recent case law is moving toward full compensation for the harm suffered: asbestos removal costs, termite treatment costs, energy upgrade costs, loss of value of the property, and even loss of enjoyment. It is no longer only a matter of compensating a lost opportunity to negotiate, but of covering the actual costs incurred to bring the property back into compliance.
The limits and proof of the harm suffered
This compensation nevertheless requires proof of real, quantified harm: a second expert opinion, invoices, works quotes, and a comparison with the market price. Without these elements, the judge may reduce the amount awarded or reject the claim. This is why it is advisable to seek professional advice promptly, whether from a specialist lawyer or from a real estate advisor near you, before taking any action.
Conclusion
Challenging a property diagnostic has become a well-regulated and increasingly accessible process, driven by the enforceability of the DPE and by case law that tends to provide better redress for diagnostic errors, whether they concern asbestos, lead or termites. Reacting quickly, gathering evidence and complying with limitation periods remain the key to asserting one's rights, whether as a seller whose liability is being challenged or as a buyer who has suffered harm. Beforehand, having a professional help secure a property valuation and the choice of diagnosticians remains the best way to avoid this type of dispute.
The expert's view
"Property diagnostics are no longer mere administrative formalities; they are full contractual documents that engage the liability of their author. Since the DPE reform in 2021, we have seen a profound change in practices: buyers are better informed and more vigilant, and no longer hesitate to commission counter-diagnostics when a result seems inconsistent with the actual condition of the property. On the seller's side, this heightened requirement encourages the choice of certified and rigorous diagnosticians, because an error can now result in legal action and substantial compensation. At Capifrance, we support our clients at every stage of the transaction to secure this technical file, from the selection of professionals to checking the consistency of the reports delivered. A reliable diagnostic protects the buyer, who purchases with full knowledge of the facts, as much as the seller, who limits the risk of a dispute after the sale. If in doubt about a diagnostic, the best approach remains to seek an outside opinion promptly rather than wait until the limitation period reduces your options for recourse."
— Frédéric Rémy, Commercial Performance Director at Capifrance
FAQ - Frequently asked questions
Can a sale be annulled because of an erroneous property diagnostic?
Annulment of the sale remains rare and is only ordered if the error constitutes a serious hidden defect (vice caché) making the property unfit for its intended use; most often, the courts favor financial compensation over outright annulment.
Who pays in the event of a diagnostic error, the seller or the diagnostician?
It depends on the origin of the error: if it results from a fault by the diagnostician, their professional liability insurance provides compensation; if the seller knew of the defect and concealed it, their personal liability may be engaged in parallel.
How long do you have to challenge a property diagnostic?
The period is five years from the discovery of the error for an action relating to the DPE, and generally two years from the discovery of the defect for asbestos, lead or termite diagnostics.
How can you prove that a diagnostic is erroneous?
You need to have a counter-diagnostic carried out by a different certified professional, and gather all useful supporting documents: energy bills, works quotes, the sale advertisement and the notarized deed of sale (acte authentique), in order to demonstrate the discrepancy between the initial report and the actual condition of the property.
Can an erroneous DPE lower the negotiated sale price?
Yes, in the event of a proven error, the buyer may obtain compensation corresponding to the costs necessary to bring the property into line with its actual energy performance, which may be negotiated directly with the seller or obtained through the courts.
Also read on the blog
- How to check the validity of a property diagnostic?
- Radon diagnostic: what sellers need to know
- Heat pumps and property sales: what impact on value and the DPE?
Author
Frédéric Rémy – Director of Sales Performance
A real estate professional with several years of experience within the Capifrance network, I would like to share essential advice with you to help you successfully complete your property project with our advisors.
