Any mechanics' liens arising as a result of repairs to or improvements of a unit by a unit owner shall be liens only against such unit. Any mechanics' liens arising as a result of repairs to or improvements of the common elements, if authorized in writing pursuant to a duly adopted resolution of the council, shall be paid by the council as a common expense and until so paid shall be liens against each unit in a percentage equal to the proportionate share of the common elements relating to such unit.