Article 858 of Civil Code

1 - The expenses of preserving, maintaining, administering and renewing the common parts shall be borne by all owners, each in proportion to his share in those parts. 2 - Nevertheless, the expenses of common services which concern certain owners or from which the benefit derived varies markedly shall be apportioned in proportion to the benefit accruing from them to each floor or apartment. 3 - All of the foregoing shall apply unless otherwise agreed.