1. Common-area maintenance documentation
Under the Ley de Propiedad Horizontal (Art. 10) the community of owners is obliged to maintain common areas in the conditions of safety, habitability, and accessibility required by law. "We maintained it" is a legal defence only if you can show it.
That means a per-element maintenance regime — pools, lifts, fire-protection systems, roofs, lighting, electrical panels, irrigation, each separately documented — and an evidentiary trail per visit: when, by whom, what was done, what was inspected, what was replaced, and what was deferred (and why). Spanish jurisprudence consistently distinguishes between documented and undocumented regimes when assigning liability after an incident.
Annual obligation: confirm coverage of every common-area element with a recurring schedule, store the supporting evidence in one place the junta can pull on demand, and align with the Ley de Ordenación de la Edificación (Art. 3, 16, 17) timeline for building-element life-cycle care. Owners who later sell rely on the same audit trail to demonstrate property condition to buyers.