In order for the framing of a pergola or overhead trellis to be excluded from lot occupancy, the cross members or lattice spacing of said pergola or trellis must be spaced greater than 24 inches on center, so as not to be treated as building area under 11 DCMR B-312, “Rules of Measurement for Lot Occupancy.”   

If the distance between rafters is 24 inches or less, the structure would be considered building area, would count toward lot occupancy, and is also subject to any applicable setback requirements.