Quote Not Honoured: Work Different From What Was Agreed

The quote specified insulation of a given thickness, a precise material brand, a defined installation method. Once the work was finished, the result doesn’t match: different materials, simplified installation, missing items. The client ends up with a project that bears no resemblance to what they signed and paid for, often without knowing how to prove it or what to do next.

The problem: paying for one quote and getting another

We see this situation constantly in our expert assessments. The quote is the contractual foundation of the project: it commits the company to specific materials, quantities, installation techniques and price. When the finished work departs from that document, it constitutes non-performance or defective performance of the contract, governed under French law by Articles 1103 and 1104 of the Civil Code on the binding force of contracts and contractual good faith. The gaps we find range from minor details (a different colour, a fitting that was never installed) to substantial discrepancies affecting the performance of the building itself: thermal insulation below what was specified, a thinner slab than agreed, or a waterproofing system that was promised but never installed.

The client faces a two-part problem: first, identifying and proving the gap between the quote and the finished work, and second, assessing the financial and technical consequences of that gap, particularly when it affects the building’s performance or durability.

Why it happens

Several factors explain these discrepancies, and not all of them stem from bad faith. Sometimes a stock shortage or unavailable material pushes a contractor to substitute a product without telling the client, wrongly assuming the swap is self-evidently equivalent. In other cases, the company underestimates the real complexity or cost of the job when quoting, then tries to cut costs later by simplifying certain items to limit its losses — a practice that remains at fault, even if understandable from the contractor’s point of view.

In more troubling cases, the substitution is deliberate from the outset: an attractive quote is built around high-quality work to win the contract, with the contractor already knowing the actual execution will differ. This amounts to a breach of the duty of information and contractual good faith, and in the most serious cases can constitute misleading commercial practice under Article L441-1 of the French Consumer Code when the client is a private, non-professional buyer.

Finally, a recurring factor is vagueness in the quote itself: descriptions that are too generic (« enhanced thermal insulation », « quality flooring ») leave room for interpretation that makes discrepancies easier to get away with, for lack of a precise technical reference (brand, product reference, thickness, standard).

What can be done

The first step is to gather all the contractual documents: the signed quote, any amendments, and written exchanges (emails, texts) mentioning changes to the work. This documentation is essential to draw a precise comparison between what was planned and what was actually delivered. The gap then needs to be established objectively, which often requires technical checks that the client alone cannot carry out: measuring insulation thickness, identifying the exact nature of an installed material, or checking compliance with a standard referenced in the quote.

Once the gap is documented, a formal notice sent to the contractor by registered letter with acknowledgement of receipt formalises the claim and opens a phase for amicable negotiation. If no agreement is reached, the client can bring the matter before the competent civil court — the Grasse judicial court for the Alpes-Maritimes — to seek either conforming completion of the work, a price reduction proportional to the gap found, or damages if the discrepancy has caused technical harm (for example, degraded thermal performance).

How an independent expert helps

Independent expert assessment is often what turns a feeling of being misled into a solid case. We carry out a joint on-site survey comparing precisely what the quote specifies (materials, thicknesses, installation techniques, brands where relevant) against the actual state of the work. Depending on the case, this involves core samples, thickness measurements, and compliance checks against the relevant French technical standards (DTU 45.10 for insulation, DTU 13.3 for concrete slabs, DTU 25.41 for metal-frame partition linings, among others), using Trotec measuring equipment to objectively document thermal or moisture discrepancies.

Our report also puts a figure on the financial impact of the gap: the cost of the missing work, the loss in value from a lower-grade material, or the cost of bringing the work up to standard if remedial work is required. Backed by objective market references, this costing gives the client a solid basis for negotiation or for legal action. With fifteen years of experience in public works and project management, we can quickly tell the difference between a minor, acceptable adjustment and a genuine breach of contract.

Frequently asked questions

Does signing the quote mean I have to accept any change the contractor decides to make?
No. Any substantial change to the work specified in the quote should, in principle, be subject to the client’s express agreement, ideally formalised through a written amendment.

How can I prove the materials installed aren’t the ones specified in the quote?
A joint technical survey, involving measurements and where necessary core samples, can objectively establish the actual nature of the materials and compare them against the contractual specifications.

Can I demand the non-conforming work be redone entirely?
You can seek conforming completion, a price reduction, or damages depending on the severity of the gap and its technical impact, assessed on a case-by-case basis.

Does a minor discrepancy justify legal action?
Not necessarily. Expert assessment is precisely what allows the severity of the gap to be objectively qualified, helping you choose between amicable negotiation and court proceedings.

📅 Mis à jour le 25/09/2026 — Cassini Expertise, expert bâtiment indépendant (06·83·13·40).