Fixed-Price Contract: When Additional Works Disrupt the Contractual Balance

Imagine: you are having a house built in Colmar. The builder gave you a fixed-price quotation for €200,000. During the works, you request a modification to the roof, then the addition of a conservatory, then a change of tiling. The builder agrees by riders. In the end, you receive an invoice for €280,000. The builder tells you: "The initial fixed price is no longer valid, the works have changed too much." Is he entitled to do so?

This is exactly the question that the French Supreme Court decided on 20 March 2002 in a case concerning a building site in Wittenheim. The judges upheld the reasoning of a Court of Appeal which had found that, given the scale and cost of the modifications, the fixed-price contract had lost its binding nature. A landmark decision that changes the game for both owners and contractors.

For the fixed price is a sacred principle in construction law: the price is fixed and cannot be revised, except in exceptional cases. But this judgment reminds us that if the modifications are so profound that they disrupt the contractual balance, then the fixed price ceases to apply. Explanations follow.

The Facts: A Story That Happens Every Day

In 1993, the company CCTG, owner of a property in Wittenheim, entrusted a group of companies with renovation and extension works. Among them, the company Barbot CM (formerly Tourangelles CMT) was responsible for the roofing lot. The contract was concluded at a fixed price: 10 million francs (approximately €1.5 million).

But very quickly, difficulties accumulated: unforeseen defects, modifications requested by the project owner, technical adaptations. The parties then signed a global agreement: CCTG paid compensation of 10 million francs to the companies and agreed to eleven riders to the contract for additional works representing several million francs more.

Despite this agreement, Barbot CM claimed in court payment of the balance of its works, arguing that the fixed price was no longer applicable. CCTG refused, invoking the principle of the fixed price. The Tribunal de Grande Instance of Mulhouse, then the Court of Appeal of Colmar, ruled in favour of Barbot CM: the fixed price had fallen due to the disruption of the contractual balance. CCTG appealed to the Supreme Court.

The Reasoning of the Court – Analysed

The Supreme Court dismissed CCTG's appeal. It upheld the reasoning of the Court of Appeal: it "could find, without deciding a serious dispute, that the numerous difficulties encountered had disrupted the contractual balance and that the modifications made during the execution of a complex and evolving project had, by their nature, cost and scale, caused the contract to lose its initial fixed-price character."

The legal basis is Article 1793 of the Civil Code, which establishes the principle of the fixed price: the price is fixed and cannot be increased on the grounds of an increase in labour or materials. But case law admits exceptions: the disruption of the contractual balance, i.e., modifications that, by their importance, change the very nature of the project. Here, the judges considered that the global agreement and the eleven riders demonstrated that the parties themselves had recognised that the initial contract was no longer appropriate.

CCTG argued that the agreement was a settlement that resolved everything. But the Court of Appeal found that this agreement did not cover the balance of the price, because it compensated the companies for their difficulties, without setting a new fixed price. In other words, the parties had reverted to a "cost-plus" contract for the additional works. The Supreme Court approved: this is a sovereign assessment of the trial judges, which cannot be challenged.

This judgment is not a reversal but a confirmation of consistent case law since the 1970s. It reminds us that the fixed price is not an absolute protection for the project owner: if you modify the project too much, you lose the benefit of the fixed price.

What This Changes for You – Concretely

If you are a landlord in Colmar or elsewhere, this decision concerns you directly. You sign a fixed-price contract for works? Beware: if you request substantial modifications (change of materials, extension, structural rework), the contractor may legitimately claim an additional price, even without a signed rider, if the amount of the modifications exceeds a certain threshold. In practice, courts often consider that beyond 10 to 20% of the initial price, disruption is established.

For a buyer in a co-ownership in Wittenheim: if you buy a unit in a building that has undergone major works, check whether the fixed price was respected. If the syndic has signed numerous riders, the final price may differ greatly from the initial quotation, and additional calls for funds may be made to you.

For a contractor: this decision is a weapon. If the project owner imposes multiple modifications, document them in writing and have riders signed. But above all, do not fear losing the fixed price: if the changes are major, you can charge on a cost-plus basis. However, be careful: the judge assesses on a case-by-case basis. A simple rider of 5% is not enough.

Four Tips to Avoid This Type of Dispute

• Draft a clear contract from the outset: the fixed-price contract must precisely describe the included services and exclude unforeseen works. Provide for a revision clause in case of major modifications.
• Keep track of riders: each modification, even minor, must be the subject of a rider signed by both parties. Set an amount and a deadline. Without a rider, the project owner may refuse to pay.
• Keep photographic and written records: in case of dispute, evidence is essential. Keep all emails, meeting minutes, photos of the works. In Colmar, a client showed me a file of 200 photos that tipped the scales.
• Consult a lawyer before signing a global agreement: the compensation agreement in this case was interpreted as a recognition of disruption. If you sign without advice, you risk losing your rights. A 30-minute consultation can save you a €50,000 bill.

Further Analysis: Related Case Law and Developments

This decision is part of a consistent line. Already in 1995, the Supreme Court held that additional works representing 25% of the initial amount disrupted the contractual balance (Civ. 3e, 22 November 1995, No. 93-20.887). More recently, in 2018, it specified that the disruption must be assessed objectively, regardless of the good faith of the parties (Civ. 3e, 21 June 2018, No. 17-19.438).

The trend is therefore towards a relative protection of the fixed price: it does not withstand massive modifications. Courts are increasingly attentive to the economic reality of the site. For the future, one can expect judges to require even stricter traceability of riders and agreements. The advice: leave nothing to word of mouth.

In Practice: What to Do

FAQ:

1. Can I challenge an additional invoice if I signed a rider? Yes, if the rider was not freely consented to or if the price is abusive. But this is a difficult challenge. It is better to negotiate before signing.

2. What if the contractor refuses to finish the works without an increase? Put him on formal notice by registered letter. If he insists, you can apply to the interim relief judge for a provisional payment (advance on the price).

3. What is the time limit for action? In construction law, the action for payment is barred after 5 years from the completion of the works. For latent defects, it is 2 years.

4. Do I have to go through a lawyer? Before the Tribunal Judiciaire, yes, for disputes over €10,000. For interim relief, no, but it is strongly recommended.

5. Can the judge reduce the amount of additional works? Yes, if he considers the price excessive or the works unnecessary. But he must give reasons for his decision.

Are you in a similar situation? A first 30-minute consultation with Maître Zakine (€45) can save you months of proceedings – and often much more. Book an appointment →