(1) A party wall on a property line need not be constructed as a firewall provided it is constructed as a fire separation having not less than a 1 h fire-resistance rating if,
(a) the property line is between houses, or
(b) the property line is between dwelling units in a building of residential occupancy, other than a house, in which there is no dwelling unit above another dwelling unit.
(2) The wall described in Sentence (1) shall provide continuous protection from the top of the footings to the underside of the roof deck.
(3) Any space between the top of the wall described in Sentence (1) and the roof deck shall be tightly filled with mineral wool or noncombustible material.