Who is involved and in what capacity
Some participants are required by law, others chosen. The difference determines what is negotiable.
The architect is required, and the monopoly covers two things. Every client, public or private, must call on them for the preparation of drawings and for supervision of the execution of the works. An appointment limited to drawings is incomplete in the eyes of the law.
The incompatibility with contracting is absolute and general. The Court of Cassation has held that it is not confined to combining roles within one concrete project: an architect cannot be a contractor elsewhere. The rationale is independence, since they supervise execution.
Regulatory roles are added depending on the project: safety and health coordination, energy performance officer, inspection bodies. Their content is defined by a text, not by contract.
One rule runs through this branch: a role not entrusted does not disappear; it is taken on by someone else, often without a corresponding contract. In separate trades, whatever is entrusted to nobody remains with the client, coordination included.
These points are developed in the branch on the parties and their roles. The overlaps between roles are set out there.
When the Breyne Act applies
This is the core of the guide, and the strongest protection in Belgian construction law. It concerns the Breyne Act.
Four cumulative conditions: a dwelling to be built or under construction, situated in Belgium, principally intended for habitation, and all the works entrusted to a single party.
The fourth is decisive and counter-intuitive. Protection depends neither on value, nor complexity, nor the standing of the professional, but on the number of contracting parties. Appointing several firms takes the project outside the act, with no partial protection possible.
Hence a paradox: the legally most protective arrangement is the one leaving the least technical control, and conversely. That is not an inconsistency: the act protects whoever relies entirely on a professional.
What it provides
It is mandatory and criminally sanctioned. A contrary clause has no effect, and the professional cannot opt out.
Five protections: control of payments with a deposit cap, a financial guarantee, a written contract with prescribed minimum content, double acceptance with a period between, and control of price revision. They are of public order and cannot be negotiated away.
And an often decisive indirect effect. A developer who acted only as vendor does not answer for ten-year liability, having not participated in the act of building. Except where the sale falls under the Breyne Act. The protection therefore goes well beyond insolvency risk.
The exclusions
Construction and property professionals acting on their own account, through an irrebuttable statutory presumption admitting no contrary evidence. Public institutions. Property not intended for habitation. Property completed at the time of sale.
Outside the scope does not mean without protection, but protection must then be negotiated and written rather than imposed.
These points are developed in the branch on the Breyne Act. The conditions of application are set out there.
What a contract must say
A contract protects not by its length but by its precision on a few points. Those points can be counted on one hand.
Eight clauses matter: exact scope of the appointment, price and how it is determined, revision regime, periods and their starting point, acceptance arrangements, hierarchy of documents, treatment of variations, insurance and certificates.
Three are most often omitted: treatment of variations, without which works proceed with no price basis; the starting point of periods, without which delay cannot be established; and the hierarchy of documents.
Some frequent clauses serve no purpose and create an illusion of protection: limitation of ten-year liability, a clause setting aside the Breyne Act within its scope, a general good-faith clause, a reference to terms not annexed.
Subcontracting reaches the client
Two mechanisms cross the absence of a contractual link. They concern subcontracting and the direct action.
Direct action allows an unpaid subcontractor to proceed against the client, but only up to what remains owed to the contractor when the action is brought. What has been paid escapes it, which makes the payment schedule a protection. Since 2023 that mechanism has been integrated into the general law of obligations.
Joint liability for social and tax debts, which the withholding obligation allows one to escape.
These points are developed in the branch on contracts. The decisive clauses are listed there.
What acceptance triggers
Acceptance is the act with the heaviest consequences on a project. It starts the time limits running and transfers the risks.
It is a unilateral act of the client, refusable only on legitimate grounds, and completion may be recorded in the presence of defects. Acceptance with reservations is therefore the normal situation.
Provisional acceptance produces five immediate effects: record of completion, transfer of risk and custody, cover of unreserved patent defects, opening of the testing period, and financial effects.
The most damaging trap: unless proved otherwise, occupying or using the property amounts to tacit acceptance of provisional acceptance. Accepting does not require occupying, but occupying amounts to accepting.
When the ten-year period starts
Sources diverge, and case law settles the point. The exact reach of provisional acceptance remains debated.
The parties may have the ten-year period run from provisional acceptance, provided they have clearly decided to give it an effect of approval. The starting point follows approval, not the label, and a clause bringing the date forward without conferring that effect is fragile.
Under the Breyne Act, final acceptance may occur only after one year, with an additional condition on common parts in multi-occupancy buildings.
What is not reserved is covered. Latent defects and serious defects within ten-year liability escape that effect, the regime being of public policy.
These points are developed in the branch on acceptance. The effects of each acceptance are set out there.
Who answers for what
Three regimes layer according to the nature of the defect. They differ in their duration and their object.
| Regime | Defects | Duration |
|---|---|---|
| Patent defects | visible at acceptance | covered unless reserved |
| Minor latent defects | slight, undetectable | contractual, adjustable |
| Ten-year | affecting soundness or stability | ten years, of public policy |
The test for being brought in is participation in the act of building, not the nature of the contract. Contractor, architect, consulting engineer and inspection body are covered.
The public policy character of ten-year liability produces three effects: no clause can exclude or limit it, no waiver is valid, and the period is one of forfeiture interrupted neither by interim proceedings nor by a request for an expert.
Compulsory insurance does not cover everything. Two distinct regimes, the architects' from 2006 and the contractors' from 2017, and in both cases protection against insolvency, not against fault.
These points are developed in the branch on liability and insurance. The applicable periods are compared there.
A reform under way
A decisive current point for anyone concluding today. It concerns the guarantee regime of the Breyne Act.
The Court of Justice of the European Union condemned Belgium on 26 February 2026, holding the Breyne Act's guarantee regime contrary to the freedom to provide services.
The reasoning is coherent: the difference between a full guarantee for non-approved parties and limited security for approved contractors paradoxically results in better protection for a purchaser contracting with a non-approved contractor. A reform of the scheme is therefore expected.
The rules remain in force pending amendment, and the act's other protections are unaffected. But the state of the law must be checked before concluding, as the article on developments to monitor recalls.
The method, in summary
Six rules, applicable to any Belgian project. They order the checks from signature to acceptance.
1. Choose the arrangement knowingly, since it determines whether the Breyne Act applies and hence the whole regime.
2. Ask the act's five questions before structuring, not before signing.
3. Write the scope positively and negatively, and provide for the remainder.
4. Never let occupation occur before acceptance, occupation amounting to tacit acceptance.
5. Reserve what is visible, since what is not reserved is covered.
6. Check insurance before construction, not after a loss.
The detailed methods appear in the articles on checking whether the Breyne Act applies and on preparing a provisional acceptance. The questions are listed there in order.
This guide reflects rules and case law at the date of checking and serves as orientation. It does not constitute legal advice and does not replace assessment of the individual case.