What is the Construction Start Act and Why Is It Essential for Your Project?

CONSTRUCTION

Apr 29

Written By Francisco Javier Muñoz Fuentes

When you finally have your building permit in hand and everything is ready to begin construction on your home or renovation, it’s time to formalize one of the most important documents in the entire process: the Construction Start Act ("Acta de Inicio de Obra"). This procedure often raises some questions, so we’ll explain what it is, when it’s signed, who is involved, and why it’s crucial for the legal compliance of your project.

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1. WHAT EXACTLY IS THE CONSTRUCTION START ACT?

It is an official document that certifies the actual date on which construction work authorized by the municipal license begins. This act also formalizes who the professionals responsible for overseeing and supervising the construction are: the site manager (architect) and the execution manager (technical architect or "aparejador"). It also identifies the construction company, or the developer if it’s a self-build project.

This document must be signed by all parties involved and then validated ("visado") by the corresponding Professional Associations (Architects’ Association and Technical Architects’ Association). With this, the start of the construction work is officially recorded with local authorities, and the professional oversight (Dirección Facultativa) ensuring correct execution of the project is activated.

2. WHY IS IT MANDATORY TO SIGN IT?

Signing the Construction Start Act is not just a formality—it is a legal and administrative requirement to ensure the project is properly supervised and complies with the urban planning obligations established in the permit. Without this signed and validated act, you cannot prove that your construction started within the authorized time frame, which could lead to permit expiration or legal sanctions.

Furthermore, the act is necessary for processing other essential documents, such as the Final Completion Certificate, and for requesting the First Occupancy License at the end of the project. It’s also required to obtain compulsory insurance like the ten-year insurance ("seguro decenal"), particularly for new constructions in areas such as Marbella, Estepona, or Mijas.

3. WHO MUST SIGN THE CONSTRUCTION START ACT?

Several key figures in the building process must sign the Construction Start Act. The architect (site manager) and the technical architect or "aparejador" (execution manager) are the primary professionals responsible. Both must be registered and authorized to practice.

The developer—often the private property owner—must also sign. If a construction company has been hired, it must be identified in the document as well. In some cases, the health and safety coordinator also signs if the project requires such oversight.

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4. WHEN SHOULD THE CONSTRUCTION START ACT BE SIGNED?

The right time to sign the Construction Start Act is just before any physical work begins on the site: earthworks, foundations, fencing, etc. It’s not advisable to delay this procedure or begin construction informally, as municipalities like Málaga, Marbella, or Sotogrande frequently carry out urban inspections and may require documented proof that all protocols have been followed.

In some municipalities, such as Marbella or Estepona, in addition to the validated act, an express communication of project commencement is required via a formal declaration or prior notification. It is essential to coordinate these steps with your architect to avoid delays or penalties.

5. WHAT INFORMATION DOES THE CONSTRUCTION START ACT INCLUDE?

Generally, the Construction Start Act includes:

Developer’s details.
Exact location of the construction site.
Building permit information.
Technical project data.
Names and registration details of the responsible professionals.
Name of the construction company, if applicable.
Planned start date and estimated duration.

All information must align with what was approved in the building permit and technical project.

CONCLUSION: THE FIRST STEP TO START YOUR PROJECT

Although it may seem like a minor procedure, the Construction Start Act is a key document in the construction of your home or project. It marks the official beginning of the work and ensures everything is done under proper technical supervision and in compliance with the law.

Are you starting your project in Málaga, Marbella, Estepona, Mijas, or Sotogrande? At Munoz Barcia Architects, we’re happy to guide you—contact us!

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