A new building, a transformation or a renovation. On paper it seems simple: you sign an offer, the contractor executes, you pay. In practice it rarely goes that smoothly. The contractor delivers less than promised, asks for additional works that were nowhere stated, or halts the site without explanation. The architect draws the plans but does not show up on the site. A subcontractor suddenly demands payment directly from you, even though you have already paid the main contractor. And afterwards it turns out that a defect only surfaces after three years — are you still in time?
Belgian contracting law governs all these situations, but it is not a single statute. It rests on classic provisions of the old Civil Code (Articles 1779, 1787, 1792, 1794 and 1798), on the reformed Book 5 of the Civil Code on obligations, on an extensive arsenal of case law of the Court of Cassation, and on the Code of Economic Law for B2B relationships. And it is on the eve of a major reform: the legislative proposal for Book 7 of the Civil Code of 16 April 2024 seeks to integrate contracting into a general services contract, together with deposit and mandate.
This guide gives you, as a client (whether you are a private individual, an entrepreneur or an association of co-owners), a foothold at every phase of your construction project. From the first contract to acceptance, and from the duty to warn during the works to the ten-year liability thereafter.
What is a construction contract?
A construction contract is a contract by which one party (the contractor) undertakes to execute a specific work for another party (the client or principal) against payment of a price. The law also calls this "hire of work" (Articles 1779, 3° and 1787 of the old Civil Code). It is distinguished from the employment contract by the absence of a relationship of subordination, and from the sales contract in that the main purpose is a performance, not the transfer of property.
The construction contract is a consensual contract: it comes into being through the agreement of wills, without formal requirements. The Court of Cassation confirmed in its judgment of 5 December 2022 (case no. C.22.0134.N) that a construction contract can even be proven by the conduct of one of the parties, such as having additional works carried out. An extrajudicial admission (Article 8.31 of the Civil Code) provides the same proof as a judicial admission.
The price is an essential element. If it is not fixed at the conclusion of the contract, it must at least be determinable. A contractor may fix the price unilaterally, but the judge has a marginal power of review on the basis of good faith, which prohibits the contractor from demanding an abnormally high price.
Before the works: contract, price and information
Written or verbal?
The law does not require a writing for the construction contract itself. But without a written record, every dispute becomes a battle of proof. For consumers, specific information duties of the business apply in addition on the basis of the Code of Economic Law (Articles V.2 and VI.37 of the Code of Economic Law): the principal characteristics of the service must be clearly communicated before the conclusion of the contract. A contractor or architect who does not comply with that transparency requirement risks having his fee or price clauses rejected afterwards for lack of clarity.
For those without a written contract, read our guide on how to prove your agreements without a written contract with your contractor.
The fixed price and Article 1793 of the Civil Code
When a fixed price ("lump sum") is agreed for the erection of a building, Article 1793 of the old Civil Code applies today. That article provides that a price increase is only possible when the client agrees in writing to changes or enlargements and when the price of those changes is agreed. It is more than a rule of evidence: without a writing, any price increase is unlawful.
The upcoming Book 7 of the Civil Code abolishes this article. Not because the protection of the client becomes less important, but because it is captured via the general precontractual duty to inform (Article 5.16 of the Civil Code). Until then, the written agreement remains THE rule.
Unfair terms also between businesses
Since 1 December 2020, a doctrine of unfair terms applies to B2B contracts (Articles VI.91/1 to VI.91/10 of the Code of Economic Law). Clauses that create a manifest imbalance between rights and obligations are null. This also applies to construction contracts between businesses, and even to an association of co-owners with a professional destination of more than 25%. Read about this in our guide on unfair terms in construction contracts between businesses.
During the works: additional works, collaboration and the duty to warn
Additional works: not simply added to the final invoice
A fixed price remains a fixed price. If additional work arises, Article 1793 of the old Civil Code requires a written agreement and an agreed price. But practice is more nuanced: the Court of Cassation accepts that the conduct of the parties suffices as proof. A client who has additional works carried out and allows the contractor to continue working can hardly refuse payment afterwards.
At the same time, the Antwerp Court of Appeal imposes on 16 April 2024 (DAOR 2025, issue 153, 20) a clear duty to inform on the contractor. In the absence of clear communication about additional works, the consumer can assume that all executed works were in the original offer. The contractor who remains silent pays himself. For the full analysis, see when a contractor may charge you additional works.
When several contractors work on one site
If you work with a main contractor who himself hires subcontractors, the coordination lies with that main contractor. But if you work directly with several contractors (for example a shell builder, a joiner and an installer), the coordination lies with you, the client, according to Article 7.4.10 of the draft Book 7 of the Civil Code.
This is not a free pass for the individual contractors. Article 7.4.28 of the Civil Code provides that they are obliged to collaborate, with mutual obligations of information, advice and warning. The Court of Cassation already applied that rule in its judgment of 20 May 2021. In practice: in the case of cracks in a concrete floor on which underfloor heating was later placed, you no longer have to designate a single individual culprit — you can hold the contractors jointly liable for the lack of coordination. See how coordination and liability work in the case of several contractors on your site.
The contractor as watchdog
In addition to his executive task, the contractor has a duty to inform and warn. He must point out to you the risks he knows as a professional and that you, as a layperson, cannot necessarily assess. The Ghent Court of Appeal held on 4 October 2023 (TBO 2023, issue 6, 279) that a contractor who carries out excavation works near gas or electricity pipes has a duty to consult, locate and coordinate, with sanctions in the event of failure. Read our in-depth analysis in what consequences it has if your contractor did not warn you.
Acceptance and approval
Acceptance is the pivotal moment of every construction contract. It marks the transition from the execution phase to the warranty phase, and it determines from which moment which periods run.
Classically, a distinction is made between the provisional acceptance (the works are completed, small remaining points may still be mentioned in a report of reservations) and the final acceptance (all remaining points are resolved, the warranty period begins to run). The provisional acceptance today counts as the starting point of the ten-year liability of Articles 1792 and 2270 of the old Civil Code.
The draft Book 7 of the Civil Code works with a monistic system. Article 7.4.9 provides that the principal accepts the completed assignment at the time of delivery, expressly or tacitly. Acceptance without reservation implies that the client confirms that the assignment has been delivered on time and is free from any defect that can come to light upon an attentive examination by a reasonable client. Hidden defects do not fall under it.
Article 7.4.24 of the Civil Code links the transfer of property and risk to acceptance. The materials the contractor delivers become the property of the client as they are incorporated into a good over which the latter has a right of ownership. Only upon acceptance does the risk pass to the client.
What if there are defects after acceptance?
Not every defect that surfaces after acceptance falls under the same regime. Belgian contracting law distinguishes two major categories, plus a third regime in the upcoming Book 7.
Light hidden defects
Shortcomings that are not serious enough to threaten the stability of the building, but which you would never have accepted had you known of them, fall under the light hidden defects. The Antwerp Court of Appeal described them on 26 April 2022 (TBO 2023, issue 5, 250) as defects in or around the structure that fall outside ten-year liability, but which are sufficiently serious to influence acceptance. They are subject to a double deadline: the claim must be brought within a reasonable period after discovery, and it falls under the ten-year limitation period of Article 2262bis of the Civil Code from acceptance. Read more in how much time you have for light hidden defects after acceptance.
Ten-year liability for stability-threatening defects
For serious defects that affect the solidity of the building or a main component, Articles 1792 and 2270 of the old Civil Code apply. This liability lasts ten years from the acceptance of the works and binds both the contractor and the architect. Crucially: the Court of Cassation confirmed on 10 February 2022 (case no. C.19.0594.N) that this liability touches public order. Clauses that contractually limit or exclude it are null — regardless of whether the works have been accepted or not. For the full analysis, see our guide on the ten-year liability of the contractor and architect.
The upcoming monistic system
The draft Book 7 of the Civil Code simplifies and aligns with the law of sale. Article 7.4.17 provides a conformity period of ten years from acceptance for all conformity defects. Article 7.4.18 requires notification within a reasonable period after discovery. Article 7.4.19 subjects the claim to a limitation period of two years from notification, suspended during negotiations or expert investigation. For stability-threatening defects, Article 7.4.49 retains a separate regime: a ten-year forfeiture period from acceptance, no notification obligation, absolute nullity of exoneration clauses.
When you want to end the collaboration with the contractor
A client who wants to stop the works often thinks in a single concept: "I am ending it". Legally there are three different routes, with fundamentally different consequences.
Termination by notice on the basis of Article 1794 of the old Civil Code
Article 1794 of the old Civil Code gives the client the right to unilaterally terminate the construction contract, even without fault of the contractor. The price then remains in a sense due: the contractor must be compensated for his expenses, his supplied performances and, save for contrary usage, his loss of profit. The Antwerp Court of Appeal held on 27 June 2023 (NjW 2024, issue 509, 831) that a contractually stipulated termination indemnity is not a penalty clause, is not subject to review under Article VI.83 of the Code of Economic Law and is not capable of reduction.
Rescission for non-performance
When the contractor seriously fails, the client can claim the rescission of the contract on the basis of Article 5.90 of the Civil Code. Unlike termination by notice, rescission operates retroactively: the contract is deemed never to have existed, with restitution of mutual performances. The Brussels Court of Appeal confirmed on 15 December 2022 (T.Aann. 2024, issue 2, 166) that rescission remains possible even after the contract has been terminated by notice.
Extrajudicial rescission by notification
Since the reform of Book 5, the creditor can rescind the contract by means of a written notification to the debtor (Article 5.93 of the Civil Code). The notification must mention the shortcomings and is done at his own risk. In the event of a dispute, the judge reviews afterwards whether the conditions were met. An irregular or abusive extrajudicial rescission is ineffective (Article 5.94 of the Civil Code). Read about this in how to correctly show a contractor the door — rescission or termination.
The architect and his responsibility
For works requiring an environmental permit, Article 4 of the Act of 20 February 1939 prescribes the assistance of an architect — both for drawing up plans and for supervising the execution. Article 21 of the Rules of Professional Conduct prohibits the architect from accepting an assignment for execution plans without being simultaneously entrusted with the supervision.
What if the client discharges the architect from the supervisory task? The Court of Cassation nuanced on 15 September 2022 (case no. C.22.0066.F) that this does not automatically lead to the nullity of the construction contract. And on 29 September 2022 (case no. C.21.0491.F), the Court clarified that the discharged architect has no civil-law obligation to ensure that another architect takes over the supervision — only an obligation to inform the permit-issuing authority and the Council of the Order. For the full analysis, see which risks you run with an architect without site supervision.
In addition to these classic rules, the general precontractual duty to inform (Article 5.16 of the Civil Code) and the possible nullity for error (Article 5.33 of the Civil Code) apply. And since the Act of 31 May 2017, a mandatory professional liability insurance for ten-year civil liability applies to architects and contractors active in the construction sector.
Subcontractors and the direct claim
When a main contractor does not pay his subcontractor, Article 1798 of the old Civil Code gives a statutory security: the subcontractor can hold the client directly liable for payment for the performances carried out for the benefit of that client. The Constitutional Court held in its judgment no. 81/2021 of 3 June 2021 that this direct claim can also be exercised extrajudicially, via a registered letter.
The claim works as long as the main contractor's claim on the client is available. The Antwerp Court of Appeal pointed out in its judgment of 22 October 2020 (RW 2022-23, issue 26, 1028) the impact of a bankruptcy: from the judgment declaring bankruptcy, the claim becomes unavailable and the direct claim can no longer be exercised. The Antwerp Business Court confirmed on 22 December 2022 (TBO 2023, issue 3, 128) that Article 1798 of the Civil Code is of mandatory law — the parties cannot contractually exclude the direct claim. For the complete picture, see how a subcontractor can hold a client directly liable.
What changes with the upcoming Book 7 of the Civil Code?
The legislative proposal for Book 7 of the Civil Code of 16 April 2024 seeks to integrate contracting into a general services contract, together with deposit and mandate. The main lines: simplification, restructuring, coherence, and alignment with the law of sale. The innovations are largely of a formal nature and tie in with the Belgian legal tradition.
Concrete consequences for contracting: Article 1793 of the old Civil Code is abolished, Article 1795 of the old Civil Code (on the death of the contractor) disappears, ten-year liability is recast as "stability-threatening conformity defects" (Article 7.4.49), the duty of collaboration between contractors is codified (Article 7.4.28), and the direct claim of the subcontractor is extended and modernised (Article 7.4.31).
When does it enter into force? The legislative proposal must still fully run the parliamentary course. Under the previous government, it did not get through; under the current government, it is back on the table. A definitive date does not yet exist, and even if the legislative proposal is adopted, a transitional regime will apply. For ongoing contracts and projects, the old Civil Code therefore remains the reference for now. A specific risk zone is building without a valid permit and what that does to your construction contract.
When to engage legal assistance?
Not every disagreement with a contractor or architect calls for a lawyer. But it does: as soon as you consider a notice of default, want to invoke a rescission, or are confronted with a ten-year liability claim. Likewise, in case of doubt about the validity of general terms, in the case of direct claims by subcontractors, or in the case of permit problems after the start of the works, legal advice is not a luxury.
Reius Lawyers assists private individuals, companies and associations of co-owners in every kind of construction dispute. We work both preventively (contract review, site follow-up) and curatively (notice of default, summons, representation in expertise). Contact us at info@reius.be or via the contact form for an initial analysis of your case.
In re. In jure — Thorough in the facts. Considered in the law.