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  • The Builder
  • Conditions of building contract
  • Conditions of sub-contracting
  • The Subcontractor
  1. Constructor / Builder

The builder or contractor is the building agent who assumes, contractually before the developer, the commitment to execute with human and material means, from own or others, the works or part of them subject to the project and to the contract.

The main obligation  of the builder is of useful result towards the promoter, to complete the work executed, however, the contractor assumes diverse obligations and responsibilities:

– in the contractual field, it bears the risk and cost of the loss or destruction of the work until its delivery except for late handing over (CC art.1544, 1588 s. and 1596;  LOE art.17);

– in the workplace (may incur guilt in choosing and in monitoring);

– in relation to materials (whether supplied or laid by the builder himself);

– in relation to capital, its financing, etc.


Inspired by the principle of risk and adventure of the contractor, the work contract is also known as a company contract, alluding to the different obligations and responsibilities assumed by the contractor under the contract and the fact that the contractor must put the necessary human and material resources to obtain the committed result.


The builder is required to have the qualification or professional training that qualifies for the fulfillment of the conditions required to act as a builder.

In the absence of specifying the qualification or professional training to which reference is made and there is no specific qualification whose purpose is to train contractors, the legal provision relating to the enabling qualification of the builder is empty of content, remaining a mere declaration of good intentions.

Since there is no official title to be a contractor, you can currently be a contractor any person, natural or legal, with  legal capacity to be bound and with a professional (and economic) capacity sufficient for the fulfillment of the work contract.

However, where appropriate, the contractor must be subject to the obligations established by the Autonomous Communities for the exercise of the profession of builder, since they are the only ones competent to dictate rules in relation to the exercise of non-qualified professions in the field of construction.

There are some official qualifications, vocational training, related to various material activities of construction (for example realization and plans of work, masonry, etc.). In this sense, there are certificates of professionalism that confirm the competence and experience acquired by some construction technicians.


In addition to the requirement relating to the qualification or professional training enabling to be a builder, the following obligations correspond to it:

  • The execution of the work subject to the project, the applicable legislation and the instructions of the construction manager and the director of the execution of the work, in order to achieve the quality required in the project.

The execution of the work by the contractor must conform to the following parameters:

– the order received from the principal or the promoter;

– the project drafted by the designer/architect;

– the lex artis of the builder, which forms part of the contract (CC art.1258), that is, he must observe the usual rules and good practices specific to his profession;

– the applicable legislation, in particular that relating to construction products, quality control, safety and health, prevention of occupational risks, etc., and must have the required authorizations, permits and licenses, etc.;

– to the instructions of the promoter, generally channelled through the facultative management, that is, the director of work and the director of execution of the work.

As already analyzed before, the contractor does not comply with developing an activity with due diligence, it is necessary to achieve the result established in the contract. Therefore, the risk of the  loss of the thing/works until the delivery of the work runs at his expense.

The contractor cannot limit himself to executing the technical instructions since his position as an expert means that he is able to assess the feasibility of the  instructions and orders received, as well as the suitability of the construction materials if supplied by the principal/promoter. It is the obligation on him to warn the principal when the instructions or orders are incorrect or unfeasible and is, therefore, in his right not to carry out or execute the orders when in his opinion they are incorrect or unfeasible.


The contractor must obey the instructions of the promoter, however, it is not possible for him to allege and hide behind the fact that he does what the technicians order him in case of trying to avoid his possible responsibility in relation to the works.

  • The appointment of the construction manager who assumes the technical representation of the builder in the work and who, due to his qualification or experience, must have the appropriate training according to the characteristics and complexity of the work.

The head of works is not required to have an academic qualification . He is usually, therefore, a technical architect or person of great experience in the world of construction.

It is necessary to be able to give orders to his subordinates that the construction manager knows the construction that is intended to be executed and is able to order in advance the human and material means necessary to fulfill and execute the work as agreed by the contractor and the principal in the contract.

  • The allocation of human and material resources that the importance of the work requires. The contractor must assign to the work the human and material means necessary to achieve the result in accordance with the contractual agreement.

The builder does not usually develop his activity directly, but does so by acting through his empresarial structure. Therefore, the  total or partial subcontracting of the works is possible, provided that the requirements contained in L 32/2006, which regulates the figure of the subcontractor in the construction sector, are met, unless said faculty has been expressly excluded in the contract, or unless the principal awards or commissions all the works to the contractor on the basis of the latter’s personal conditions.

  • The formalization of the subcontracting of certain parts or facilities of the work within the limits established in the contract and in Law 32/2006 .

Subcontracting is included among the obligations of the contractor, however, it is not so much an obligation as a faculty of the contractor.

The contractor is directly responsible  , to the owner of the work, for the work that the subcontractors perform. In turn, if the work was adjusted in a manner, the subcontractor can exercise a subrogatory and subsidiary action against the same owner of the work to reclaim what the contractor owes him.

  • The signing of the act of staking or beginning of the works and the act of receipt of the work. The act of reconsideration must be signed by the contractor and by the optional management, that is, the construction manager and the director of the execution of the work.

The stakeout must be carried out by the builder as part of the execution of the work.  The staking report must state whether or not the work is appropriate and, if appropriate, the staking act serves as  the formal start of the work.

Likewise, it is an obligation of the contractor to sign the act of receipt of the work  , which must be signed, at the same time, by the contractor and by the promoter (LOE art.6). If reservations are recorded in the receipt record  , once these reservations are corrected, the contractor must sign the act of correction (LOE art.6.2.d).

  • Provide the construction manager with the necessary data for the execution of the documentation of the executed work. The contractor must deliver to the construction manager the information and documentation necessary for the preparation by him of the documentation related to the work executed (LOE art.12. 3.f).
  • The subscription of the guarantees provided for in nº 1816 s. This obligation refers to the insurance of material damage , surety or financial guarantee that the builder must subscribe in guarantee of material damage due to defects or defects of execution that affect elements of completion or finishing of works and that must be compensated during the period of one year from the completion of the works and their delivery to the promoter.

It is possible to replace  the subscription of this insurance by a withholding by the promoter of 5% of the amount of the material execution of the work during the entire warranty period. It must be understood, even if the LOE does not say anything, that it would also be possible for the contractor to substitute the subscription of the aforementioned insurance by the delivery to the promoter of  a bank guarantee guaranteeing at least 5% of the amount of the material execution of the work during the period of one year, by means of which they would be compensated,  where appropriate, material damage caused to the building by defects or defects in its execution that affect elements of completion or finishing during the aforementioned year.

The promotor may expressly agree with the contractor that he is the policyholder on behalf of the contractor with respect to (LOE art.19. 1.b and c and 19.2(a):

– material damage insurance or surety insurance to guarantee for 3 years the compensation for damage caused by defects or defects of the constructive elements or installations that cause non-compliance with the requirements of habitability; and

– material damage insurance or surety insurance to guarantee 10 years the compensation of material damage caused to the building by defects or defects that have their origin or affect the foundation, supports, beams, slabs, load-bearing walls or other structural elements, and that directly compromise the mechanical strength and stability of the building.

2. Subcontractor

The subcontractor is the natural or legal person who contractually assumes to the contractor or to other principal subcontractor the commitment to carry out certain parts or units of work, subject to the project by which its execution is governed. The variants of this figure can be those of the first subcontractor (subcontractor whose principal is the contractor), second subcontractor (subcontractor whose principal is the first subcontractor), and so on.

L 32/2006 regulates subcontracting in the construction sector and aims to improve the working conditions of the sector, in general, and the health and safety conditions of workers  in the sector, in particular. This Law represents a radical change in relation to the pre-existing model, since it addresses for the first time, and in a strictly sectoral way, a regulation of the legal regime of subcontracting that, recognizing its importance for the construction sector and specialization for the increase of productivity,  establishes a series of guarantees aimed at avoiding that the lack of control in this form of productive organization causes objective situations  of risk to the safety and health of workers, in a country like Spain, which continues to register a very notorious occupational accident rate due to its figures and severity.

This law, which is strictly sectoral, applies to contracts that are concluded, under subcontracting, for the execution of the following works carried out in construction works:

– excavation;

– landworks;

– construction;

– assembly and disassembly of prefabricated elements;

– fitting-outs or installations;

– transformation;

– rehabilitation;

– repair;

– decommissioning;

– demolition;

– maintenance;

– conservation and painting and cleaning work;

– sanitation.

Requirements for contractors and subcontractors

A series of requirements are established for contractors and subcontractors, in order to avoid the participation of companies without a minimum organizational structure to ensure that they are in a position to meet their obligations to protect the health and safety of workers.

In order for a company to be able to intervene in the subcontracting process in the construction sector, as a contractor or subcontractor, it must meet the following requirements:

  • Possess their own productive organization, have the necessary material and personal means, and use them for the development of the contracted activity.
  • Assume the risks, obligations and responsibilities of the development of the business activity.
  • Directly exercise the power of organization and management over the work carried out by its workers on the site and, in the case of self-employed workers, execute the work with autonomy and own responsibility and outside the scope of organization and management of the company that has hired him.

In addition to the above requirements, companies that intend to be hired or subcontracted for work on a construction site must:

  • Prove that they have human resources, at their managerial and productive level, who have the necessary training in prevention of occupational hazards, as well as a preventive organization appropriate to L 31/1995, for the prevention of occupational risks.
  • Be registered in the Register of Accredited Companies (nº 1631). This registration is made ex officio by the competent labour authority, on the basis of the employer’s declaration referred to in the following paragraph.

Contractors or subcontractors must prove compliance with the above requirements by means of a declaration signed by their legal representative made before the Registry of Accredited Companies. Registration is carried out ex officio by the competent labour authority, on the basis of such a declaration.

In addition, companies whose activity consists of being hired or subcontracted habitually for the performance of work in works in the construction sector must have, in the terms determined by regulation, a number of workers hired indefinitely that  is not less than 10% during the first 18 months of validity of this rule, nor 20% during the months of 19th to 36th, nor 30% from the 37th month, inclusive. For these purposes, in worker cooperatives, workers are counted in a similar way to employees, in the terms determined by regulation.

Subcontracting regime

The excess in subcontracting chains, especially in the construction sector, operates to the detriment of business margins and the quality of the services provided progressively to the point that, in the last links of the chain, such margins are practically non-existent, favoring submerged work, just in the final element that must respond to the safety and health conditions of the workers who perform the works. Therefore, the alleged excesses of subcontracting can facilitate the appearance of practices incompatible with occupational safety and health.

However, subcontracting, as a form of productive organization, cannot be limited, except under the conditions and in the cases provided for in L 32/2006. Thus, the subcontracting regime in the construction sector in general is as follows:

  • The promoter can contract directly with as many contractors as it deems appropriate, whether natural or legal persons.
  • The contractor can contract with the subcontractors or self-employed workers the execution of the works that he has contracted with the promoter.
  • The first and second subcontractors can subcontract the execution of the works that, respectively, they have contracted.
  • The third subcontractor may not subcontract the work he has contracted with another subcontractor or self-employed worker.
  • The self-employed worker may not subcontract the work entrusted to him or to other subcontractors or other self-employed workers.
  • Likewise, subcontractors cannot subcontract, whose productive organization put into use on the site consists, fundamentally, in the contribution of labor, understood as the one that for the realization of the contracted activity does not use more of its own work equipment than hand tools, including portable motorized tools, although they have the support of other equipment of work other than those indicated, provided that these belong to other companies, contractors or subcontractors, of the work.

Notwithstanding the foregoing, when in fortuitous cases duly justified, due to requirements of specialization of the works, technical complications of the production or circumstances of force majeure through which the agents involved in the work may go through, it is necessary, in the opinion of the optional management, the contracting of some part of the work with third parties,  Exceptionally, the subcontracting established at an additional level may be extended, provided that its prior approval and the cause or reasons for it are recorded by the optional management in the subcontracting book.


The exceptional extension of subcontracting does not apply  in the cases referred to in points e) and f) above, unless the motivating circumstance is that of force majeure.

The contractor must inform the health and safety coordinator and   the workers’ representatives of the different companies included in the scope of execution of his contract that are listed in the subcontracting book, the exceptional subcontracting.

Likewise, the contractor must inform the competent labour authority of  the aforementioned exceptional subcontracting by sending, within 5 working days of its approval, an information indicating the circumstances of its need and a copy of the annotation made in the subcontracting book.

Registration of Accredited Companies

For the purposes of the provisions relating to the subcontracting regime, it is foreseen the creation of the Register of Accredited Companies, in dependence on the competent labor authority, understood as the corresponding to the territory of the autonomous community where the registered office of the contractor or subcontractor company is located.

The registration in the Registry of Accredited Companies is valid for the entire national territory, being its data of public access with the exception of those referring to the privacy of the people.

By regulation, the content, form and effects of the registration in said registry will be established, as well as the coordination systems  of the different registries dependent on the autonomous labor authorities.

Obligations of contractor and subcontractor

The following obligations are established:

  • Duty of vigilance and responsibilities arising from its non-compliance. Contractors and subcontractors involved in construction works falling within the scope of L 32/2006 must monitor compliance with the provisions of L 32/2006 by the subcontractors and self-employed persons with which they contract; in particular, as regards:

– accreditation and registration obligations  (L 32/2006 art.4.2); and

– the subcontracting regime  (L 32/2006 art.5).

Subcontractors must communicate or transfer to the contractor, through their respective principal companies, if they are different from the contractor, any information or documentation that affects the above.

Without prejudice to other responsibilities established in the social legislation, the breach of the required accreditation and registration obligations or the subcontracting regime, determines the joint and several liability of the  subcontractor who has contracted incurring in such breaches and of the corresponding contractor with respect to the labor and Social Security obligations derived from the execution of the agreed contract that  correspond to the subcontractor responsible for the breach within the scope of execution of its contract, whatever the activity of said companies.

In any case, the responsibility established in the Workers’ Statuteart.43 is enforceable  when the cases provided for therein are met.

  • Have the documentation of the subcontracting. Each contractor must have a subcontracting book for any construction site falling within the scope of L 32/2006.
  • Duty of information to workers’ representatives. The representatives of the workers of the different companies involved in the execution of the work must be informed of the contracts and subcontracting that are made in it.
  • Accredit the preventive training of workers. Companies must ensure that all workers who provide services on the construction sites have the necessary and appropriate training for their job or function in the field of occupational risk prevention, so that they know the risks and the measures to prevent them.


(1) By sectoral collective agreement at the state level, systems or procedures for the representation of workers may be established through trade union representatives or representatives of a bipartite nature between employers’ and trade union organizations, in order to promote compliance with the regulations on the prevention of occupational risks  in the construction works of the corresponding territory. It can also establish training programs and specific contents of a sectoral nature and for the works of each specialty.

2) The system of  accreditation specific training may consist of the issuance of a booklet or professional card for each worker, unique and valid throughout the sector.

3) The subcontractor does not have the status of building agent under the LOE regime, which delimits the responsibility of the building agents against construction defects, being responsible for the activity of the subcontractors the builder, being contractually linked, limiting the action of the subcontractor to follow the instructions of his contractor (TS 9-10-18,  EDJ 597989).

4) Infringements of the provisions  of L 32/2006 are punishable in accordance with RDLeg 5/2000 of the consolidated text of the Law on infringements and sanctions in the social order.