Civil Code (Cap. 16), article 409

409. (1) In the absence of a mark or other proof to the contrary, a wall which serves to separate two buildings is presumed to be common up to the top, and, where such buildings have not the same height, up to one metre and eighty centimetres from the point at which the difference in height begins. (2) The part of the wall above one metre and eighty centimetres from the height of the lower building, is presumed to belong to the owner of the higher building. (3) Where there is a building on one side, and a courtyard, garden or field on the other side, the wall is presumed to belong entirely to the owner of the building. Party-wall between courtyards, gardens or fields.