The Office of Zoning Administration has reviewed several applications where a portion of a top of a building is being used as roof deck which is adjacent to a partial top story at the same level. The setback requirements for railings bordering such rooftop decks are addressed in Section C-1504.3(a) as follows: 

C-1504.3 In addition to the exemptions of Subtitle C § 1504.2, the rear, side, and open court setback requirements of Subtitle C §§ 1504.1(b)-(d) shall not apply to features meeting the following conditions: 

(a) For a rooftop deck on the highest roof a building, guardrails required by the building code that do not exceed a height of three feet, six inches (3 ft., 6 in.), when the façade is not facing a public or private street or a public park;…. 

Based on the above provision, the railings for a rooftop deck on the highest roof of the building are exempted from the rooftop setback requirements when the façade is not facing a public or private street or a public park, while rooftop decks that are either not on the highest roof level, or are adjacent to a facade that faces a public or private street or a public park, would have to provide the required setback.