Design‑build or traditional contracting: which is safer for owners in Belgium after the 2026 duty of care?

Neither model is inherently “safer.” Design‑build centralises liability with one contractor, simplifying claims but concentrating counterparty risk. Traditional contracting distributes liability but fragments enforcement. Under the 2026 Flemish duty‑of‑care rules, both models require documented subcontractor compliance checks. The safer option is whichever model the owner equips with robust contractual controls and insurance, see the Decision Framework above.

Who is liable for defects and design faults under design‑build vs design‑bid‑build in Belgium?

Decennial liability under the Loi du 31 mai 2017 (Peeters‑Borsus Act) applies to architects and contractors responsible for structural works, regardless of procurement model. In design‑build, claims are directed at the design‑builder and its insurers. In traditional contracting, the architect bears design fault liability and the contractor bears execution fault liability; the owner may need to pursue both.

Does the 2026 Flemish duty of care and chain liability change which procurement model I should use?

It does not preclude either model. However, it imposes documentary and onboarding obligations on principals and contractors in both models. Any entity engaging subcontractors in Flanders must obtain and retain identity, right‑to‑work, RSZ and insurance evidence. Failure to do so creates chain liability exposure regardless of whether the project uses design‑build or traditional procurement.

Which procurement method is faster or cheaper for Belgian projects, and when should I hire a construction lawyer?

Design‑build is typically faster because design and construction overlap. The cost comparison depends on how the contractor prices design risk and compliance obligations. Hire a construction lawyer before issuing the tender, the procurement documents set the risk framework for the entire project, and post‑tender corrections are expensive.

Is the ten‑year decennial liability avoidable by contract?

No. Decennial liability under Belgian law is of public order and cannot be excluded or limited by contractual clause. The Peeters‑Borsus Act mandates insurance cover for this liability. Parties can allocate risk between themselves contractually (e.g., indemnities), but the underlying statutory obligation to the building owner remains intact for ten years from acceptance.

What documents must I collect from subcontractors to meet the Flemish duty of care?

The Flemish implementing decision requires principals and contractors to collect and retain: identity documents, right‑to‑work evidence, RSZ (social security) registration records, proof of insurance, and Limosa declarations for posted workers. Written declarations confirming employment law compliance should also be obtained. Records should be retained for a minimum of ten years, aligned with decennial liability, to demonstrate compliance during any subsequent investigation.

Design‑Build Vs Traditional Contracting Belgium

Choosing between design‑build and traditional contracting in Belgium in 2026 demands more than a schedule‑versus‑cost calculation. Belgium’s mandatory ten‑year decennial liability regime, the Loi du 31 mai 2017 (Peeters‑Borsus Act), and the new Flemish zorgvuldigheidsplicht (duty of care) and tightened ketenaansprakelijkheid (chain liability) rules, effective 1 January 2026, have materially shifted who bears risk when subcontractors are used in either procurement model. This article gives developers, project owners, main contractors and in‑house counsel a dimension‑by‑dimension comparison, a mandatory side‑by‑side table, and an actionable decision framework so you can choose the right model and know when to engage specialist construction counsel before tendering.

Option A: Design‑Build, Single‑Point Responsibility

Under a design‑build contract, the owner engages a single entity, the design‑builder, that is responsible for both design and construction. The design‑builder either maintains in‑house design capability or subcontracts an architect or engineering firm, but the contractual risk for design errors and construction defects sits with one counterparty. In Belgium this model is increasingly used for mixed‑use developments, industrial facilities and infrastructure works where programme certainty and a single point of contact outweigh the owner’s desire for granular design control.

Pros and cons of design‑build in Belgium

Faster programme. Design and construction phases overlap, which industry observers typically associate with shorter overall delivery schedules compared with sequential design‑bid‑build procurement.
Single‑point liability. The owner directs claims for defects, including structural defects subject to the ten‑year decennial regime, at one party and its insurers, simplifying enforcement.
Cost certainty (if lump‑sum). A fixed‑price design‑build contract locks in the total cost earlier, though the design‑builder prices design risk and insurance obligations into the lump sum.
Reduced design control. The owner surrenders day‑to‑day design authority. Late specification changes are expensive and contractually constrained.
Higher compliance burden under 2026 Flemish rules. The design‑builder must demonstrate duty‑of‑care checks across its entire subcontracting chain to avoid chain liability exposure in Flanders, an administrative cost that is passed through to the project.

Typical contract clauses to include

Design responsibility & professional liability. Require the design‑builder to maintain professional indemnity insurance covering its design team and to provide evidence of the mandatory decennial insurance policy under the Peeters‑Borsus Act at contract signature.
Subcontractor audit rights. Include express rights for the owner (or its representative) to audit the design‑builder’s subcontractor onboarding records, declarations and Flemish duty‑of‑care documentation at any time during the works and for a specified period after completion.

Option B: Traditional Contracting (Design‑Bid‑Build)

In the traditional model the owner first engages a designer, typically an architect registered with the Belgian Order of Architects, to produce a complete design. The owner then tenders the construction works separately. The contractor bids on and builds to the finished design. This separation preserves the owner’s design control and allows competitive pricing at the tender stage, but it fragments responsibility: defects that fall between design and construction can trigger multi‑party disputes.

Advantages and disadvantages under Belgian law

Design control and staged approvals. The owner retains full authority over aesthetics, specifications and materials throughout the design phase. Belgian law requires an architect’s involvement for most building‑permit applications, and the traditional model keeps this relationship direct.
Competitive tender pricing. Separate tendering of construction works to multiple contractors can drive lower initial pricing, though change‑order costs may erode savings.
Fragmented liability. The architect is liable for design faults; the contractor for execution faults. Where a defect arises from an interface issue, the owner may need to pursue both parties, each pointing at the other, extending litigation timelines and requiring expert evidence on causation.
Sequential programme. Design must be substantially complete before tendering can begin, lengthening overall delivery compared with design‑build.
Chain liability applies equally. The Flemish duty‑of‑care and chain liability obligations apply to the main contractor and, depending on the contractual structure, can also expose the owner as principal, particularly where the owner directly engages specialist subcontractors.

Typical contract clauses to mitigate gaps

Design responsibility matrix. A clear, annexed responsibility matrix identifying which party is accountable for each design element, interface detail and specification reduces the scope for blame‑shifting.
Latent defects & coordination obligations. Require the contractor to report any design errors or ambiguities discovered during construction and impose a duty to coordinate with the architect, with contractual holdbacks or retention to fund remediation of latent defects discovered post‑completion.

Design‑Build vs Traditional Contracting in Belgium: Side‑by‑Side Comparison

Dimension	Design‑Build (single‑point)	Traditional / Design‑Bid‑Build
Who holds design risk	Contractor (design‑builder). Professional liabilities of the architect/engineer still apply under the decennial regime; the design‑builder’s decennial insurance is expected.	Designer holds design responsibility; contractor liable for build quality. Gaps between the two can cause finger‑pointing and longer disputes.
Liability for structural defects (decennial)	Decennial liability (10 years) attaches to builders and architects. Design‑build centralises claims on the design‑builder and its insurers.	Decennial liability applies to architect and contractor separately; owner may need to pursue multiple parties and their respective insurers.
Chain / subcontracting risk (Flanders 2026)	Design‑builder remains exposed to chain liability; must demonstrate duty‑of‑care checks over every tier of subcontractor to avoid liability for illegal employment.	Main contractor and, depending on engagement structure, the owner may face chain liability exposure; duty‑of‑care obligations apply equally in Flanders.
Cost predictability	Higher if fixed‑price; design risk and insurance costs are priced into the lump sum, which may carry a premium.	Lower early certainty; competitive tendering can reduce initial price, but higher change‑order risk and latency costs reduce savings.
Speed / programme	Typically faster, design and construction overlap.	Typically longer, sequential design, then tender, then build.
Contract drafting complexity	Requires integrated design‑builder obligations, IP/BOQ clarity, professional liability clauses and subcontractor audit provisions.	Requires clear interface agreements, design responsibility matrix, coordination clauses and design liability carve‑outs.
Dispute resolution	Often faster, single‑point responsibility simplifies remedies; adjudication or arbitration clauses are common.	Multi‑party disputes are more frequent and typically involve expert evidence on causation, lengthening resolution.
Enforceability of indemnities	Commercial indemnities are enforceable but cannot displace statutory decennial obligations; Flemish chain‑liability duties may override contractual pass‑throughs.	Same caveat: indemnities cannot remove statutory exposure; demonstrable compliance with duty‑of‑care rules is critical.
Best for	Projects prioritising time/cost certainty and single‑contact management, where the owner accepts a robust compliance and subcontractor onboarding regime.	Projects prioritising design control, competitive pricing and staged owner oversight, where the owner can accept a sequential timeline.

The key takeaway from this design‑build vs traditional contracting Belgium comparison is that decennial liability is a constant under both models, it cannot be contracted away. What has changed in 2026 is that the Flemish duty‑of‑care and chain liability rules make subcontractor documentation and auditing essential regardless of procurement route. The compliance burden is particularly acute in design‑build, where risk is concentrated with one contractor managing a deeper subcontracting chain.

Dimension‑by‑Dimension Analysis

Liability: Decennial, Professional and Chain

Belgian construction liability rests on several interlocking pillars. Understanding each is essential before choosing between design‑build and traditional contracting in Belgium.

Decennial liability, the ten‑year statutory liability for serious structural defects affecting stability, applies to architects and contractors involved in building works. The Loi du 31 mai 2017 (Peeters‑Borsus Act) made decennial liability insurance mandatory for architects, contractors and other service providers whose actions directly affect the structural soundness of a building. This obligation is of public order: contractual clauses purporting to exclude or limit decennial liability are unenforceable.

Professional liability attaches to architects and engineers for design errors. In a design‑build structure, the design‑builder typically absorbs this risk contractually, but the individual architect’s professional obligations, including mandatory registration with the Order of Architects, remain.

Chain liability for illegal employment has been significantly strengthened in Flanders from 1 January 2026 by the introduction of a formal zorgvuldigheidsplicht (duty of care). Principals and contractors who engage subcontractors in defined risk sectors, construction is explicitly included, must obtain, verify and retain specific documents from each subcontractor. Failure to demonstrate these steps exposes the principal or contractor to liability for illegal employment detected anywhere in the subcontracting chain.

Design‑build impact. The design‑builder, as the sole contractual counterparty to the owner, bears the full chain liability exposure for every tier of subcontractor it engages. Unless the contract imposes robust audit rights and the design‑builder maintains a compliant onboarding file, the owner’s recourse depends on the design‑builder’s solvency and insurance.
Traditional impact. Chain liability exposure is shared between the main contractor and, potentially, the owner (as principal) where the owner has directly engaged specialist subcontractors. The fragmented structure requires each party to maintain its own duty‑of‑care file, increasing administrative complexity but distributing exposure.

Contract clause checklist, Owners

Require evidence of decennial insurance at contract signature (Peeters‑Borsus Act compliance).
Include express subcontractor audit rights and periodic compliance reporting.
Mandate written duty‑of‑care declarations from the contractor for each subcontractor tier.
Specify contractual holdback or retention to cover latent defect remediation.
Require the contractor to notify the owner immediately of any suspected illegal employment.

Contract clause checklist, Contractors

Implement a documented subcontractor onboarding procedure covering identity, right to work, RSZ registration, proof of insurance and Limosa declarations where applicable.
Require each subcontractor to provide a written declaration confirming compliance with employment law and to accept audit obligations.
Maintain records for a minimum of ten years (aligned with the decennial liability period).
Include back‑to‑back indemnity clauses with subcontractors for chain liability exposure.
Budget for compliance administration costs in tender pricing, duty‑of‑care documentation is not optional.

Cost and Tax

The cost comparison between design‑build and traditional procurement in Belgium must account for VAT, mandatory insurance obligations and the administrative cost of compliance with the 2026 Flemish duty‑of‑care regime. Belgium applies a standard VAT rate of 21% to construction works, which applies identically under both procurement models.

Item	Design‑Build	Traditional
Standard VAT	21% on taxable supplies	21% on taxable supplies (identical)
Decennial insurance	Mandatory under the Loi du 31 mai 2017 (Peeters‑Borsus Act). Owner should require evidence of a ten‑year policy at contract signature.	Same mandatory requirement, owner must collect policy evidence from both architect and contractor.
Key cost drivers	Insurance premium for combined design and build decennial cover; contractor risk premium for absorbing design liability; compliance and onboarding administration for subcontractors.	Competitive tender pricing may produce lower initial bids; budget higher contingency for design changes, variation orders and possible multi‑party claims.

Industry observers expect that design‑build lump sums will carry a measurable premium to reflect the contractor’s absorption of design risk and enhanced compliance obligations. Owners should obtain insurer quotes specific to the project before finalising procurement strategy.

Timing and Programme

Design‑build compresses the overall programme by overlapping the design and construction phases. Early contractor engagement allows procurement of long‑lead items while detailed design is still in progress. The traditional model requires the design to be substantially complete before tendering begins, followed by a separate tender evaluation period and then construction mobilisation, a sequential process that extends the calendar.

The practical schedule advantage of design‑build is well recognised in the Belgian market, although the magnitude varies by project complexity. Owners should note that the time saved in the design‑build programme can be partially offset by the front‑loaded effort required to prepare robust tender and contract documents, particularly the subcontractor compliance framework now required under Flemish law.

Insurance and Financial Security

Both procurement models require mandatory decennial liability insurance under the Peeters‑Borsus Act. Owners should also consider requiring project all‑risk insurance, parent company guarantees from the contractor’s parent entity, and escrow or retention holdbacks to fund remediation of defects discovered after provisional acceptance. In design‑build, a single comprehensive insurance programme covering both design and construction risk is efficient but requires careful policy review to confirm there are no gaps between professional indemnity and all‑risk cover.

Enforceability and Dispute Resolution

Belgian courts have jurisdiction over construction disputes, but parties frequently agree to arbitration or, increasingly, contractual adjudication for interim binding decisions. Design‑build simplifies dispute resolution by providing single‑point responsibility, reducing the need for multi‑party proceedings and expert causation evidence. Traditional contracts with fragmented liability often lead to longer, more expensive disputes. Regardless of model, contractual indemnities cannot override the statutory decennial obligations or the Flemish chain liability regime.

Regulatory and Compliance Burden

The 2026 Flemish duty‑of‑care requirements add documentary and onboarding obligations that apply in both procurement models. Construction contracts should include compliance audit rights, CIAW (Construction Industry Activity Watch) time‑registration obligations, and express provisions requiring retention of subcontractor documentation. Contract templates that pre‑date 2026 should be reviewed and updated by specialist counsel before use in any Flemish project.

What Changes in 2026: The Flemish Duty of Care and Chain Liability

The Flemish Government adopted implementation measures that refine and strengthen ketenaansprakelijkheid (chain liability) for illegal employment and introduced a formal zorgvuldigheidsplicht (duty of care) obligation. These measures took effect on 1 January 2026, with a six‑month tolerance period (gedoogperiode) for certain documentary actions.

Under the new framework, employers and principal contractors operating in defined risk sectors, construction is explicitly within scope, must obtain, verify and retain specific documents from their subcontractors before engaging them. The required documentation includes identity verification, right‑to‑work evidence, RSZ (social security) registration records, proof of insurance, and Limosa declarations for posted workers where applicable. Principals and contractors who cannot demonstrate that they took these duty‑of‑care steps face liability for any illegal employment detected in their subcontracting chain.

The practical consequences for procurement are significant:

Contract templates must be updated. Pre‑2026 standard forms that rely on contractual pass‑through indemnities without documentary compliance provisions are now inadequate. Indemnities remain useful but cannot displace the regulatory duty‑of‑care obligation.
Pre‑qualification requirements tighten. Owners and main contractors should impose Flemish duty‑of‑care compliance as a pre‑qualification criterion in tender processes.
Subcontractor onboarding becomes formalised. A documented onboarding pack, covering all required evidence, must be completed and retained for each subcontractor and each tier of the chain.
Insurance policy review is essential. Existing liability policies should be checked to confirm they respond to chain‑liability claims arising from subcontractor non‑compliance.

The likely practical effect of the tolerance period is that enforcement authorities will focus initially on egregious cases rather than minor documentary gaps, but early indications suggest that the construction sector is a priority enforcement target. Waiting until the tolerance period expires to begin compliance is a high‑risk strategy.

Decision Framework: When to Choose Design‑Build, When to Choose Traditional

The following framework distils the design‑build vs traditional contracting Belgium analysis into actionable decision triggers. Use it to match your project priorities to the procurement model that best manages your legal and commercial risk in 2026.

If your priority is…	Choose…
Fast delivery and single‑point responsibility; you accept a higher upfront premium and stronger contractor compliance controls	Design‑Build. Ensure robust decennial insurance, subcontractor audit rights, and express duty‑of‑care clauses. Require an onboarding pack and periodic compliance audits.
Maximum design control, staged approvals and competitive pricing at tender	Traditional. Require clear interface agreements, a design responsibility matrix, and contractual holdbacks to cover latent defects and change orders.
Minimising public or regulatory chain‑liability exposure in Flanders	Either model, with controls. If you are a public body or professional principal, prefer procurement with strict prequalification and retained oversight. Insert documentary duty‑of‑care obligations and audit rights regardless of model.
Reducing litigation complexity	Design‑Build, but only if the contractor can provide insurance and compliance evidence. Otherwise enforce interface coordination and ADR clauses in the traditional model.

Choose Design‑Build when:

Programme speed is a project‑critical constraint.
The owner prefers a single contractual counterparty for claims and remedies.
The project integrates complex engineering where design‑build coordination adds value.
The owner is prepared to invest in robust subcontractor compliance infrastructure.

Choose Traditional when:

The owner requires full control over design aesthetics, specifications and materials.
Competitive pricing through separate tender is a priority.
The owner has in‑house project management capability to manage multiple contracts and interfaces.
The project involves phased design approvals that are incompatible with integrated delivery.

When to Engage a Construction Lawyer

The choice between design‑build and traditional contracting in Belgium is a legal decision, not merely a commercial one. The following situations should trigger engagement with specialist construction counsel:

Before issuing any tender. The tender documents define risk allocation for the life of the project. Procurement strategy, contract form, insurance requirements and Flemish duty‑of‑care provisions must be legally reviewed before the tender is published.
When bidding on integrated design risk. A contractor being asked to accept design‑build responsibility should have the contract reviewed to confirm that professional liability insurance, decennial cover and subcontractor obligations are adequately addressed.
When engaging cross‑border subcontractors. Complex subcontracting chains, particularly those involving posted workers or subcontractors from other EU member states, trigger Limosa declaration requirements and heightened Flemish chain‑liability scrutiny.
On discovering suspected illegal employment. Immediate legal advice is essential to manage regulatory exposure, notification obligations and contractual remedies.
When updating pre‑2026 contract templates. Standard forms drafted before the Flemish duty‑of‑care regime took effect are likely to contain inadequate compliance provisions. A legal review ensures that new regulatory requirements are properly embedded in tender and contract documents.

A construction lawyer should deliver: contract clause drafting or review, insurance adequacy assessment, a Flemish duty‑of‑care compliance checklist, and, where applicable, forensic review of tender documents to identify latent risk allocations. Find a Belgium construction lawyer through the Global Law Experts directory.

Need Legal Advice?

This article was produced by Global Law Experts. For specialist advice on this topic, contact Wim Nackaerts at Strada Legale, a member of the Global Law Experts network.