Q. What are the vertical clearance requirements for overhead conductors over a roof?

A. In general, service-drop conductor spans must maintain a minimum of 8 ft vertical clearance above the surface of a roof for a minimum distance of 3 ft in all directions from the edge of the roof [230.24(A)]. However, there are some specific exceptions to this rule.

If the slope of the roof exceeds 4 in. for every 12 in., 120/208V or 120/240V conductor clearances can be reduced to 3 ft over the roof 230.24(A), Ex 2]. If no more than 6 ft of conductors pass over no more than 4 ft of roof, 120/208V or 120/240V conductor clearances over the roof overhang can be reduced to 18 in. [230.24(A), Ex 3]. The 3 ft vertical clearance that extends from the roof doesn't apply when the point of attachment is on the side of the building (below the roof) [230.24(A), Ex 4].