Hello, Yuting:
You do need a construction permit to expand and put more levels to the villa and the surface.
First, we would need to consult the urban regulations of the specific area of the town of Getafe, where the house is located. The urban regulations are issued by the municipality, and tell us the maximum occupancy limits, levels and meters built for each specific area. In the event that the urban planning regulations allow such action, it is necessary to carry out a technical project where the architect would indicate the parameters, the area that is being expanded, calculations and technical justifications to carry out said action and to be able to request a construction permit from the city council.
Our company is specialized in such procedures and actions.
Let me know if you have any other questions or if you would like to discuss further.

Good morning
You have to define "extension".
It is not the same on the same floor as on a higher floor.
In single-family housing, or in high-rise housing.

And, yes, you always have to request a license.

Thank you.