Can a legal document be issued for the installation of a solar water heater on the roof of an apartment building, even if the necessary facilities and piping are not in place and the owners of the top floor do not consent?

In any case, for the installation of a solar water heater and the necessary related equipment and piping on a shared apartment building roof (within the roof’s slopes and stereometry), unless specifically provided for in the building regulations, the consent of the co-owners is required (e.g., installation of a solar water heater with 48 hours’ written notice to the competent urban planning authority, which is notified to the relevant police department. Ref.: par. 3, l, article 4, law 4067/11 “Installation of solar water heaters in accordance with paragraphs 2b and c of article 19.”).