Ten-Year Liability Insurance for Interior Architects: When Is It Mandatory and What Does It Cover?
Which assignments are covered, which damage is insured, the limits in older buildings, cost and insurance certificates: what the law requires of the professional and what their client can check.
In short
- An interior architect who designs or oversees building work is a “builder” within the meaning of the French Civil Code: ten-year liability insurance is then mandatory.
- For ten years after handover, it covers damage that threatens the structural soundness of the home or makes it unfit for use.
- The insurance policy must be in force when work starts on site, and the certificate must be attached to quotes and invoices.
- Practising without ten-year liability insurance is punishable by six months’ imprisonment and a €75,000 fine.
Let’s take two examples. A walk-in shower starts leaking into the flat below, three years after the work. A floor has been sagging ever since a partition wall was removed. In both cases, only one question matters: who pays for the repairs?
Very often, the answer lies with the ten-year liability insurance of the professionals who designed and carried out the work, including the interior architect. But you still need to know when they are required to have it, what their policy covers and where the guarantee stops in an older property.
What is an interior architect’s ten-year liability insurance?
It stems from the Spinetta Act of 4 January 1978. The French Civil Code makes every builder strictly liable for ten years. This applies to damage that compromises the structural soundness of the works or makes them unfit for their intended use. The client therefore does not have to prove fault: they only need to establish the damage and its link to the work carried out.
An interior architect becomes a “builder” as soon as a contract binds them to their client, the maître d’ouvrage, to design or have building work carried out (Article 1792-1 of the French Civil Code). They must then cover this ten-year civil liability with insurance. In the event of a claim, the insurer pays for the repairs, even if the professional has since stopped trading.
The ten years run from handover. This is the end-of-works inspection at which the client accepts the work, with or without snags (réserves).
When is ten-year liability insurance mandatory for an interior architect?
The title of interior architect is not regulated. So it is not the title that triggers the obligation, but the content of the assignment.
Assignments that make them a “builder”
The obligation applies as soon as the assignment involves renovation and fit-out work:
- reconfiguring rooms, adding or removing partition walls
- bathrooms, kitchens, concealed plumbing and electrical systems
- opening up a load-bearing wall, with a structural engineering firm
- project management (maîtrise d’œuvre): consulting contractors, coordination, site supervision, handover
Even without any site supervision, plans or drawings that specify inadequate waterproofing can trigger their ten-year liability. The insurer must therefore know what the assignment actually involves, not just the job title.
To combine two flats in Lyon, the atelier designed the opening in the load-bearing wall. An engineer calculated it, then a contractor carried it out. Each one was liable under the ten-year guarantee for their own part of the work.
Assignments not subject to the obligation
Colour and materials advice, choosing freestanding furniture, help with buying accessories: these assignments do not involve any building works. Professional indemnity insurance is sufficient. This is one of the differences between an interior architect and a decorator.
Self-employed interior architects (auto-entrepreneurs)
Their status makes no difference. A self-employed professional who runs a building project has the same obligation as an established practice. The difficulty is a practical one. Without a track record, insurers ask for proof of experience. They sometimes restrict the activities covered and charge high premiums from the very first year.
What the ten-year guarantee covers, and what it leaves out
Damage that is covered
In interior renovation, three situations come up often:
- water seeping under a walk-in shower and reaching the floor structure or the neighbouring flat
- a timber floor that deforms after changes to partition walls
- a concealed electrical installation that makes a room unusable
The insurance pays for the repair work, including any demolition and removal needed to reach the problem.
What is not covered
- defects recorded as snags at handover, which are primarily the contractors’ responsibility
- normal wear and tear and lack of maintenance
- activities not declared to the insurer
Renovation: the question of existing structures
In a period flat, the floors, walls and roof structure existed before the work began. The French Insurance Code excludes them from compulsory insurance, unless they are fully incorporated into the new works and become technically inseparable from them. In a ruling of 30 May 2024, the Court of Cassation, France’s highest court, confirmed that both conditions must be met.
In practice, if a bathroom refit damages an old floor, repairing that floor is not necessarily covered. Some policies offer optional “existing structures” cover. For a major renovation in one of Lyon’s older buildings, it is worth asking about.
Another limitation is more recent. Since a ruling of 21 March 2024, equipment added to an existing building is no longer covered by the ten-year guarantee unless it constitutes a structure in its own right. This applies, for example, to air conditioning or a heat pump. The client still has recourse, but they must prove fault, and compulsory insurance does not apply.
Ten-year, two-year and completion guarantees: three to tell apart
| Guarantee | Duration after handover | Who provides it | What it covers |
| Completion guarantee (parfait achèvement) | 1 year | The contractors | Defects reported at handover or appearing within the first year |
| Proper functioning guarantee (biennale) | 2 years minimum | The builders | Les équipements démontables sans abîmer le bâti : robinetterie, radiateurs, volets |
| Décennale | 10 ans | Les constructeurs, dont l’architecte d’intérieur | Les dommages qui touchent la solidité ou rendent le logement impropre à son usage |
Snags at the end of the works are therefore primarily the contractors’ responsibility. The ten-year guarantee takes over for serious damage that appears later.
The interior architect’s other insurance policies
Professional indemnity insurance covers mistakes that fall outside the ten-year guarantee. Unlike a registered architect, an interior architect is not legally required to take it out. Insurers often offer it in the same policy as ten-year liability, and a well-informed client asks for it.
Public liability insurance covers damage caused to third parties outside the scope of the service itself. For example, a visitor who falls at the atelier, or a sample that scratches a parquet floor. Legal expenses insurance covers lawyers’ and expert fees in the event of a dispute.
Building damage insurance (dommages-ouvrage), on the other hand, is taken out by the client (maître d’ouvrage). It pays for repairs covered by the ten-year guarantee without waiting for liability to be established. A private individual carrying out work on their own home faces no criminal penalty for not taking it out. In interior renovation, it is mainly worth considering when the work affects the structure and involves large sums.
How much does ten-year liability insurance cost for an interior architect?
The premium depends on several factors:
- turnover and the value of the works overseen
- the activities declared, with structural work weighing heavily
- the type of projects
- experience
- the chosen excess
For the client, this cost is built into the fees. At the atelier, professional indemnity and ten-year liability insurance are included in every proposal, as set out in the breakdown of fees.
Taking out ten-year liability insurance: points to watch
- Timing. The ten-year liability policy must be in force when work starts on site. It is this policy that covers the project for ten years, even if the interior architect later changes insurer or stops trading.
- Declared activities. Design, project management, structural work: everything must be listed in the policy.
- Limits and excesses. These should be weighed against the value of the projects overseen.
- Options. Existing structures, consequential losses, proper functioning, legal expenses: these often make the difference between two offers at the same price.
Insurers specialising in construction offer policies designed specifically for interior architects, such as the Mutuelle des architectes français (MAF). A broker can help you compare several offers before signing up.
For clients: check the certificate before signing
Since the law of 6 August 2015, the ten-year liability insurance certificate must be attached to quotes and invoices, using an official template. Check:
- the name or company name, which must match the one on the contract
- the period of validity, which must cover the date work starts on site
- the activities covered, which must match the assignment entrusted to them
- the wording “Assurance de responsabilité décennale obligatoire” (compulsory ten-year liability insurance)
- the policy number and the insurer’s contact details, so you can check if in doubt
The same check applies to every contractor. With full project management, the interior architect takes care of this during the tendering process, one of the stages of a complete renovation. Atelier Christophe Sarlandie itself has been insured with the MAF since it was founded.
If a defect appears
Send the professional a letter by recorded delivery with acknowledgement of receipt, with supporting photos, before the ten years are up. They report the claim to their insurer, who appoints an expert. The handover report, plans and site meeting minutes then make it possible to establish who did what.
What about a property in Switzerland?
Swiss law does not require any equivalent to the French ten-year guarantee. Since 1 January 2026, the five-year limitation period for construction defects can no longer be shortened by contract. For contracts signed since that date, a defect must also be reported within 60 days of being discovered. If you work with an interior architect in Geneva, it is best to ask exactly what their insurance policy covers.
An obligation tied to the assignment, not the title
As soon as an interior architect designs or manages building work, ten-year liability insurance is mandatory. For the client, it is the first document to ask for, along with the professional indemnity insurance certificate. But it does not cover everything: the older parts of the building and any added equipment are largely excluded. A project that has been studied in detail before work begins remains the best way to avoid a claim in the first place. This upfront work is part of the interior architect’s role.
Atelier Christophe Sarlandie, led by a CFAI-accredited interior architect, is based in Lyon and Divonne-les-Bains. It carries out complete renovations under full project management, insurance included. For a project with an interior architect in Lyon or the Pays de Gex, an initial consultation lays the foundations.
Book an appointment with the atelier.
FAQ: key takeaways
Does an interior architect need ten-year liability insurance?
Yes, as soon as they design building work or oversee its execution, whatever their status, including self-employed. An assignment limited to decoration is not subject to it.
Is professional indemnity insurance mandatory for an interior architect?
No, the law does not require it, unlike for a registered architect. It does, however, cover mistakes that the ten-year guarantee does not.
How much does ten-year liability insurance cost for an interior architect?
Roughly €3,000 to €6,000 a year as a base fee, plus a percentage of the value of the works, depending on the activity, the volume of work overseen and experience.
Does the ten-year guarantee cover the older parts of a renovated home?
In principle, no, unless they are fully incorporated into the new works and inseparable from them. An “existing structures” option can supplement the policy.
How do you check an interior architect’s insurance?
Ask for the certificate attached to the quote, then check the name, the period of validity and the activities covered. A reputable professional will provide their certificate without being asked.
