I know reading law is not everyone’s favourite pastime and I sympathize with that feeling, but I think it’s really important that people are aware that there are laws in Spain and that they are quite firm. They are carried out as well. Lots of court cases!
In the article below it basically says that you can sometimes alter your own apartment within all kind of limits and that you can never alter the rest of the building. The penalty is that you have to remove it, repair the damage and can be deprived of your right to use the property for up to three years. So only if the community allows you to do something very explicitly you can do that. The default is that you can’t.
Section 7
1. Owners of individual units may modify the architectural elements, installations or services of their
unit, giving proper notice to the community representative provided such work not impair or alter the safety
of the building, its overall structure, its external appearance or condition, or prejudice the rights of another
unit owner.
Unit owners shall not make any alteration whatsoever in the rest of the building. If unit owners notice the
need for urgent repairs, they shall bring it to the attention of the administrator without delay.
2. The owner and the occupant of a unit shall not carry out in such unit or in the rest of the building
any activities not permitted in the community statutes, or which may cause damage to the property or
contravene the general regulations concerning inconvenient, unhealthy, noxious, hazardous or unlawful
activities.
The president of the community, on his/her own initiative or at the request of a unit owner or occupant shall
urge the person or persons carrying out the activities banned under this subsection to desist under
admonition of court action.
Should the offender persist in his/her conduct, the president, subject to the authority of the meeting of the
owners’ general assembly, duly convened for this purpose, may undertake an injunction procedure, which,
insofar as not expressly provided for in this section, shall be settled by ordinary proceedings.
Once the action is brought, including the accreditation of the authoritative notice to the offender and the
certification of the resolution adopted by the general assembly, the judge may order as a precautionary
measure the immediate cessation of the prohibited activity, under admonition of incurring an offence of
disobedience. Furthermore, the judge may adopt any precautionary measures necessary to enforce the
injunction. The action shall be brought against the owner and, if fitting, against the occupant of the unit.
Should the court adjudge in favour of the plaintiff, it may decree, besides downright cessation of the
prohibited activity and award of damages as may correspond, the deprivation of the defendant’s right to use
the unit for no more than three years, depending on the seriousness of the offence and detriment caused to
the community. If the offender were not the owner, the judgement may definitely terminate the offender’s
interest in the unit and decree his/her immediate eviction.