Definition
Karim has just registered as a drywall fitter. His first real job: renovating a living room for a private client, partitions, lining, ceiling.
He sends his quote, and the client replies in one line, asking him to attach his attestation décennale (ten-year insurance certificate).
Karim is insured, his broker sold him a policy when he set up. It is the wrong policy, and he finds out the day before work starts.
The garantie décennale (ten-year warranty) is the liability that article 1792 of the Code civil (civil code) places automatically on any builder for ten years from the acceptance of the works, for damage that undermines the soundness of the structure or makes it unfit for its purpose.
Article L241-1 of the Code des assurances (insurance code) turns that liability into a duty to be insured.
Being a Micro-enterprise changes nothing at all: the obligation is triggered by the work you carry out, never by your status and never by the amounts you collect.
The official Service-Public fact sheet lists the auto-entrepreneur among builders, alongside the architect and the property developer.
What it covers, and from which day
The ten-year period starts the day after the procès-verbal de réception (works acceptance report) is signed.
It covers serious defects: cracks that threaten the structure, foundations, framework, utility networks and drainage, access roads.
It also covers structures with foundations, such as a conservatory, a terrace or a sunken swimming pool.
And it covers equipment that cannot be separated from the building, like embedded pipework, flooring, central heating or wiring buried in the walls.
It applies to new builds, and also to extensions and substantial renovation of an existing building.
On the paperwork side, the certificate must reach the client before the site opens, and be attached both to the Quotation and to the invoice, where it joins the Mandatory invoice details you already carry.
The client, for their part, must take out assurance dommages-ouvrage (structural damage insurance): it pays for repairs without waiting for liability to be shared out, then claims back from the ten-year insurer.
Many private clients never take it out, and the penalty for going uninsured does not reach them when they are building the home they will live in themselves.
The client is then left with your ten-year cover alone to fall back on: that is why Karim is being asked for his certificate so insistently.
Two dates decide everything, and they are not the ones people expect.
What counts is not the date of the damage, but the date the site opens, which must fall inside the policy period. A cancelled policy therefore keeps covering the sites opened while it was running; conversely, a site opened with no cover will never be rescued by a policy taken out afterwards.
The second date is just as harsh: only the works declared in the policy are covered.
A drywall fitter who agrees to build a conservatory without telling the insurer is working with no cover on that particular site, while still paying the premium.
And going uninsured is not a mere oversight: article L243-3 of the Code des assurances makes it a criminal offence, punishable by imprisonment and a fine.
What it really costs in a micro-enterprise
Take a full year of Karim's: 30,000 € collected in 2026, from craft services falling under BIC (bénéfices industriels et commerciaux, industrial and commercial profits).
His Social contributions are calculated at the overall 2026 rate of 21.2%.
On top of that come the CFP, the contribution à la formation professionnelle or vocational training contribution, at 0.3% for a craftsman, and the chamber of trades levy at 0.48% in standard-law departments.
That makes 21.98% in 2026, which comes to 6,594 € for the year.
Those last two lines do not fall due from day one: the CFP assumes revenue was declared in the previous calendar year, and the chamber levy is only charged from the second year of activity, never below 5,000 € of revenue.
That levy is also higher in Bas-Rhin, Haut-Rhin and Moselle, where local law applies. Income tax sits in none of these rates.
Then there is the insurance premium, and this is where the scheme bites.
Once the 6,594 € of contributions are paid, Karim is left with 23,406 €, and everything comes out of that: tools, the van, income tax, the ten-year premium.
The Standard allowance replaces every real cost with a flat percentage, the ten-year premium included: it is deducted nowhere. As for the amount, be wary of pages quoting a price.
It depends on the trade, the techniques used, how long you have been established and the revenue you declare to the insurer, and no national scale exists.
Ten-year warranty, professional liability and subcontracting
The most common mix-up sets the ten-year warranty against Professional liability insurance. They cover different moments.
Professional liability answers for damage caused to others while you work: the tool that falls on a car, the water damage in the flat below.
The ten-year warranty answers for the structure itself, once delivered and accepted.
A Business package insurance policy often bundles several covers into one contract, but it removes neither obligation: read what the policy actually covers, not the name on the cover page.
One last misunderstood case is the subcontractor. They fall outside the ten-year warranty, having no direct contract with the client.
That is no shelter: they remain liable towards the main contractor, who will pass the cost back, and most principals ask for a certificate before letting anyone onto the site.
Frequently asked questions
I am a micro-entrepreneur, is the ten-year warranty really compulsory for me?
Yes, as soon as you carry out construction, extension or substantial renovation work.
Your tax and social scheme plays no part in it: the obligation comes from the nature of the works and the contract binding you to the client, not from your status.
What happens to the cover if I change insurer or stop trading?
Sites opened while a policy was running stay covered by that policy, even after it is cancelled or the business is closed.
The client then deals directly with the insurer named on the certificate handed over before the site opened.
Is every building job concerned?
No. The warranty covers structures and equipment that cannot be separated from the building.
Purely decorative work that is easily removed falls outside it, but the boundary is decided case by case: describe every type of job precisely to your insurer before accepting it.
Can I deduct my insurance premium from the revenue I declare?
No, and this is a general rule of the micro scheme: you declare what you collect, without subtracting any expense.
The flat-rate allowance is meant to stand for your costs, whether they are in fact much lower or a great deal heavier than it.