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Main obligation of the contractor



You can read about these obligations below. This way you know what is expected of you from the contractor and how he can avoid problems with the client:

  • Perform the agreed work

  • Deliver the works on time

  • Respect the predetermined budget

  • The duty of safekeeping and return of the thing

  • Indemnify the client against hidden defects

Perform the agreed work

It is the main obligation of the contractor to carry out the work completely and in accordance with the contract. He must work out his assignment according to the rules of the art, with materials that are suitable for the purpose for which they are intended.

If the client writes to the contractor to modify/improve certain works, he can investigate whether the client's comments are correct on the basis of the building contract and the applicable standards in the sector. If this is the case, he must comply and adapt his working method.

The notification obligation of the contractor - (an extract from the Flemish agency VLAIO)

As a professional, the contractor must provide the client with the necessary information, advice and even forecasts. This reporting obligation of the contractor is based on good faith. It follows indirectly from his status, which makes him a professionally and technically more competent co-contractor than the client. If the contractor knows, or as a professional should know, that the work will lead to a defective result, he may not simply carry out the work, given the principle that he must perform contracts in good faith.

Deliver the works on time

The contractor must carry out and complete the work within the time frame agreed with the client.


In order to avoid discussion at a later stage, it is advisable to make proper agreements about this in the building contract.


For example, it is best to stipulate a start date and determine how long the work will take.


In many building contracts, a compensation for delay is also agreed per day that the work exceeds the predetermined duration. It is recommended to also include a provision about weather delays in the contract, eg between 07:00 and 17:00...4hrs of rain per day or more.


This way you are covered if the contractor cannot work from 4hrs of rain per day due to weather conditions.

If, for whatever reason, the contractor will not meet the predetermined schedule, it is advisable to communicate transparently about this with the contractor. He can then transfer an adjusted schedule and try to limit the delay and damage as much as possible. 


If the contractor does not keep the client informed of the progress of the works and the proposed schedule is grossly ignored due to your fault, this may be grounds for the client to dissolve the agreement at his expense.

The works must be inspected upon delivery. The client is obliged to make delivery and the associated inspection possible. If the client has any comments on the handover, he must have these noted in the provisional handover report.


The visible defects for which no comments were made upon delivery will be considered accepted, the client can no longer contact you for this.

Respect the predetermined budget

The building contract usually contains how the price will be determined: for a fixed price, at a unit price or on a cost-plus basis.

If the works still exceed the agreed price, there is a chance that the client will protest the relevant invoices. In the absence of protest and unconditional payment, the invoice is deemed to have been accepted. The client cannot go back on this afterwards.

The duty of safekeeping and return of the thing

While the contractor is carrying out the work, he is responsible for the safekeeping of the building built or to be renovated. During storage, he must take care of the building of the client with all the care of a good family man. For example: during roofing work, ensure proper closure in case of rain.

This retention obligation is a best efforts obligation. This means that the contractor must have done everything possible to properly preserve the building. It is up to the client to prove that the contractor has failed to meet this retention obligation. Nevertheless, it is in the contractor's interest to ensure that he can demonstrate that he has taken the necessary precautions.


It can also be useful to regularly take photos of the precautions taken by the contractor and/or to communicate these with the contractor, e.g. by mail.

The contractor must keep the structure so that he can return it to the client at the end of the works.


This obligation to return is an obligation of result. This means that the contractor must prove that he has always taken the legal or contractually prescribed measures for storage. If the contractor cannot make a return because this is due to an external cause, such as fire or theft, the contractor must also provide proof of this.

Indemnify the client against hidden defects

The contractor must deliver the works without hidden defects. If hidden defects occur that were already present in the case at the time of delivery, the client can hold the contractor accountable for this.


The contractor is clearly liable for a guarantee and must repair the defects. He must also be responsible for the damage that is the immediate and direct result of the defective execution of the works.

The client must bring legal action with regard to the hidden defects within a reasonable period of time after discovering the defect.

You can find out what these terms are in the topic about the defects below.

It is possible that defects manifest themselves after the delivery of your works. The question is how long the client can knock on your door for these defects.

A distinction must be made according to the nature of the defect. It is:

  • The visible flaws

  • The hidden flaws

In this last category, a distinction must be made between the light hidden defects and the "heavy" hidden defects, ie the hidden defects that affect the stability.

The visible flaws

These defects are visible upon delivery. Ex: crack in the window after installation, bubbles in the paint, ...

If the client has not made any reservations for the visible defects at the time of delivery, these are covered. The client can no longer claim any compensation for this.

However, if comments regarding the visible defects were made in the official report of the delivery, the client can still turn to you during the common law period of ten years. This term is subject to interruption or suspension.

The client must bring this claim within a reasonable period of time after discovering the defect. If the client waits an unreasonably long time to initiate the procedure, the court will rule that the claim is inadmissible.

The hidden flaws

slight hidden flaws:

These defects are not visible upon delivery and do not affect the strength of the building, e.g. chipping of concrete, cracks in the floor and cracking that do not affect stability; non-functioning of sanitary installations; insufficient cooling or shading; problems with the acoustics,…

Here too, the client must bring the claim within the common law term of ten years. This period is also susceptible to interruption or suspension.

The client must bring this claim within a reasonable period of time after discovering the defect. If the client waits an unreasonably long time to initiate the procedure, the court will rule that the claim is inadmissible.

serious” hidden defects

The said serious hidden defects are governed by a legally established ten-year liability.

To fall under this ten-year liability regime, the defect must meet the following conditions (art 1790 and 2270 of the Civil Code):

  • The defect must be serious and hidden
  • A serious defect affects the strength or stability of the building, or at least a significant part of it. To be hidden, the defect must not have been visible when the works were delivered.

  • The defect must affect the building or a large work that forms a whole with the building.

This concerns the building itself and all works and installations that are necessary or essential for a building. Ex: a wall, the roof, load-bearing pillars, ...

  • There must be an error in the execution

The contractor must have made an error in the performance of his task. For example: wrong or improper foundations, crooked walls, severe moisture and mold formation, ...

The stability must therefore not be due to a so-called “foreign cause”, ie a cause that has nothing to do with the execution of the works. (e.g. subsidence, later renovations, obvious lack of maintenance).

The contractor is also liable for the materials used by him. So if there is a defect in this, one can knock on the contractor's door. He can then only defend himself by demonstrating that it was absolutely impossible for him to detect that defect.  This is called invincible ignorance. The contractor will have to provide proof of this himself.

  • Often not just the contractor but shared liability

Often  there is shared liability with other construction specialists, such as specialized engineering firms or the architect. The architect has an audit duty. This obliges him or her to follow up the works of the contractors and to supervise key phases in the construction process.

If a defect meets the above conditions, the client can hold the contractor and architect/engineer jointly liable for ten years. This is the so-called ten-year liability,

  • The claim must be effectively lodged within ten years – a notice of default is not sufficient – neither is a pure claim to appoint an expert

This ten-year expiry period begins to run upon acceptance of the works. However, it is possible that the building contract stipulates that this period does not start with the handover but with the provisional handover (if a double handover is provided for). Such a clause in the agreement is valid.

The fact that there is an expiry period implies that the claim must be filed within the period of ten years. It is therefore not sufficient that a notice of default has been sent, an effective legal action must have been instituted on the merits of the case.

This may occur, for example, if only a claim for the appointment of an expert has been filed in preliminary relief proceedings. If the expertise drags on for a long time, it is possible that the 10-year term will be reached during the expertise.


If the client has not yet filed his claim for compensation for damage because he is waiting for the result of the expert investigation, he will be too late.

  • What can be claimed from the contractor? Reparation in kind or compensation.

In principle, the contractor is  obliged to repair the defective work in kind. This applies insofar as it is still useful. Moreover, if the recovery would cost disproportionately much, there is disproportionality.


It is not excluded that it could be claimed that this repair may be carried out by another contractor (Article 1144 of the Civil Code)  if the error made is so unforgivable that the client may state that it has lost all confidence in the contractor. may be subject to a judge's decision.

If recounting in kind is still possible, or not advisable, the contractor will have to compensate for the damage.

  • From 01/07/2018, every contractor is obliged to take out insurance to cover this ten-year liability!

This was imposed by the law of May 31, 2017 :

The contractor must provide proof of insurance to the client and the architect before the start of the works. The architect is also obliged to request this proof if you do not provide it spontaneously.

In addition, in the context of the site notification obligation , the contractor must also provide this proof to the NSSO.

If the contractor nevertheless starts work without the insurance, he runs the risk of criminal conviction and fines of up to € 80,000.


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