Since 21 March 2024, equipment fitted to an existing house, a heat pump, a stove, air conditioning, solar panels, no longer falls under the decennial warranty or the two year warranty of proper working order if it does not itself constitute works. The owner must prove fault by the installer, and compulsory decennial insurance can no longer be called on.
The problem as an owner meets it
A house from the 1980s. The owner has the boiler replaced with a heat pump, or photovoltaic panels fitted to the roof, or a stove connected to the existing flue. Three years later the equipment no longer works properly, or causes water ingress, or consumes twice what was promised. The installer stops answering. The owner turns to the company decennial insurance, certificate in hand, and is told the cover does not apply.
That answer, which looked arguable until 2024, is now usually correct. The Third Civil Chamber has changed its position, and the change has direct financial consequences for tens of thousands of energy renovation projects.
What the law said before 2024
From 2017, the Court of Cassation had held that damage affecting items of equipment, whether separable or not, original or fitted to an existing building, fell under decennial liability where it rendered the works as a whole unfit for their purpose. The solution was affirmed in several reported decisions, then extended to items installed on works existing before the site opened, except those which, wholly incorporated into the new works, became technically indivisible from them.
The purpose was twofold, and the Court set it out itself: to simplify, by no longer distinguishing according to whether the item was original or added to an existing building, and to give better protection to employers increasingly carrying out renovation or home improvement works.
A first narrowing came in 2022: damage affecting an item not intended to function, added to an existing building, falls exclusively under ordinary contractual liability, whatever its seriousness, tiling bonded to a screed and plasterboard partitions not being intended to function (Cass. 3e civ., 13 July 2022, no. 19-20.231, reported). Equipment intended to function therefore remained within the decennial field, thermal and solar installations first among them.
The reversal of 21 March 2024
In a decision reported in the Bulletin, the Third Civil Chamber abandoned that construction. The reasoning is explicit and worth following, because it illuminates the scope of the new rule.
The Court first finds that the objectives pursued in 2017 were not met. It had to clarify the scope of those rules repeatedly, which fed litigation instead of drying it up. And the case law begun in 2017 did not result in greater protection for employers or in better compensation than they could already obtain under other insurance cover.
From this it draws the rule: if items of equipment installed by way of replacement or addition on existing works do not themselves constitute works, they fall neither under the decennial warranty nor under the two year warranty of proper working order, whatever the seriousness of the damage, but under ordinary contractual liability, which is not subject to compulsory builders insurance (Cass. 3e civ., 21 March 2024, no. 22-18.694, reported).
A final point, decisive in practice: the new case law applies to pending proceedings, the Court having held that it causes no disproportionate interference with legal certainty or with the right of access to a court. Cases begun before 2024 on the basis of the decennial warranty were therefore weakened mid course.
Where the dividing line now runs
Everything turns on a single question: does the installation itself constitute works.
Equipment simply connected to the existing building, fitted without significant intervention in the fabric, is not works. It is otherwise where the installation requires genuine construction work: removing and reinstating the roof covering, creating service runs, foundations or a masonry base, altering the structure. The assessment is concrete and rests on technical findings, which gives expert evidence a central role from the outset.
Qualification as works is not the only filter. Where the equipment performs an enclosing or roofing function, it enters article 1792 through that door. The Court has held that an established risk of fire in a building roof renders it unfit for its purpose in itself, in a case on internal combustion of photovoltaic panel connection boxes, where no fire had started (Cass. 3e civ., 21 September 2022, no. 21-20.433, reported).
Conversely, a third filter can take out of the decennial field an installation that had entered it. Article 1792-7 of the Civil Code excludes items of equipment, accessories included, whose exclusive function is to allow a professional activity to be carried on in the works. The Third Civil Chamber quashed a court of appeal decision applying the decennial warranty to a photovoltaic installation on the ground that it also formed the roof, without establishing that the panels causing the damage, although fixed to steel trays forming the roof, were not devoid of any enclosing or roofing function and intended exclusively for a professional activity of producing and selling energy (Cass. 3e civ., 19 February 2026, no. 24-10.702).
An owner who sells his output to an operator must therefore expect that provision to be raised against his claim, even where the panels physically form part of the roof.
What the owner now has to prove
On contractual ground the presumption disappears. Fault by the installer, damage and causation must be established. In equipment installation cases, fault is generally demonstrated on three registers: failure to follow good practice and the manufacturer instructions, sizing unsuited to the building, and breach of the duty to advise, particularly where the professional sold a quantified energy saving that does not materialise.
That last point is often the most productive. An installer who produced a cursory thermal study, promised a reduction in consumption and fitted undersized equipment to a poorly insulated house incurs liability, and the sales material or the itemised quotation then measures what was undertaken.
As to time, article 1792-4-3 of the Civil Code confines within ten years of acceptance liability claims against the builders designated in articles 1792 and 1792-1 and their subcontractors, apart from claims governed by articles 1792-3, 1792-4-1 and 1792-4-2. The window is therefore not as short as is sometimes said, but it presupposes an identified acceptance, which brings one back, once again, to the question of the date.
Consequences for renovation professionals
The reversal shifts the insurance risk. Compulsory decennial liability insurance, provided for by article L. 241-1 of the Insurance Code, covers liability founded on the presumption of articles 1792 and following. If the work no longer falls under that presumption, it falls outside compulsory insurance and must be covered, if at all, by ordinary professional indemnity insurance.
Two checks are therefore needed for an installer. First, that his professional indemnity policy covers damage occurring after acceptance to equipment fitted to existing buildings, which is not automatic. Second, that the list of his declared activities matches what he actually does, because litigation about undeclared activity remains fully alive for works that stay within the decennial field.
On that last point, a recent decision calls for nuance in proportional reasoning. The Court quashed a court of appeal decision limiting the insurer cover to 9.06 per cent of the loss, corresponding to the share of the price of the works falling within the insured activity alone, without examining whether the covered defects on their own justified demolishing and rebuilding the works (Cass. 3e civ., 12 March 2026, no. 24-10.927).
What to do in practice
For an owner facing failed equipment fitted to an existing building, the useful sequence is short. Gather the quotation, the invoice, the sales material and any study, because those are what fix the undertaking. Have the defect and its cause technically recorded, by a heating engineer or a design office, before anything is removed. Write to the installer relying on contractual non performance, not the decennial warranty, so as not to open the argument on ground already lost. And approach the company professional indemnity insurer, whose details appear on the certificate given with the quotation.
Where the installation involved heavy work, removing the roof covering, creating service runs, a masonry base, the question whether it constitutes works remains open and is worth putting, because it reopens the decennial warranty and compulsory insurance. That is the main judgment call in the case, and it turns on technical findings, not on the type of equipment.
Frequently asked questions
Does a heat pump fitted to an existing house fall under the decennial warranty?
No, if it does not itself constitute works. Since the decision of 21 March 2024 such equipment falls under ordinary contractual liability, whatever the seriousness of the damage. The position would be different if the installation required construction work making it works in its own right.
Does the reversal apply to pending disputes?
Yes. The Court of Cassation expressly held that the new case law applies to pending proceedings, since it causes no disproportionate interference with legal certainty or with the right of access to a court.
Is the decennial insurance certificate given by the installer now useless?
It retains its value for works that remain within the decennial field, and it is still an indicator of seriousness. But it does not guarantee cover for damage affecting equipment fitted to an existing building that does not constitute works. The professional indemnity certificate should be requested in addition.
Are photovoltaic panels treated differently?
They combine the difficulties. If they are integrated into the fabric and perform a roofing function, the decennial warranty may apply, an established risk of roof fire on its own rendering the building unfit for its purpose. But if their exclusive function is to allow a professional activity of producing and selling electricity, article 1792-7 excludes them.
Can damage to works insurance still be called on?
Only for damage of the kind for which builders are liable under article 1792. If the equipment falls outside the decennial field, damage to works cover is not intended to prefund the repair.
How long is there to sue the installer?
Article 1792-4-3 of the Civil Code confines liability claims against builders and their subcontractors, outside the statutory warranties, within ten years of acceptance of the works. The date of that acceptance still has to be established, and it may be tacit.