Overhead service wire clearances over roofs and yards
Overhead service wires must be at least 8 ft 6 in. above a roof, with exceptions. Above ground, minimums range from 10 ft at the drip loop to 18 ft over public streets and 24 ft 6 in. over railroad tracks.
What the code requires
Overhead service conductors, the overhead wires that bring power to a building, must not be readily accessible. 230.24 sets minimum clearances above roofs and above the ground for services of 1,000 V or less.
Above a roof, the wires must be at least 8 ft 6 in. above the roof surface, and that clearance must be kept for 3 ft in all directions from the roof edge. The code lists five exceptions to the roof clearance; all five are summarized below.
Above final grade: 10 ft at the service entrance, the drip loop and pedestrian-only areas (only for messenger-supported cable at 150 V or less to ground); 12 ft over residential property, driveways and commercial areas without truck traffic, at 300 V or less to ground; and 15 ft over those same areas above 300 V to ground.
18 ft is required over public streets, alleys, roads, truck parking areas, non-residential driveways and cultivated, grazing, forest or orchard land, and 24 ft 6 in. over railroad tracks. Clearance over swimming pools follows 680.9.
On the job
- A service mast that is too short, so the drop runs closer than 8 ft 6 in. over a low-slope roof, is a common correction.
- A drip loop lower than 10 ft above grade.
- A service drop crossing a driveway lower than 12 ft.
Exceptions that matter
- Where the roof area gets pedestrian or vehicle traffic, the clearance above it must instead meet the ground clearances in 230.24(B).
- At 300 V or less between conductors on a roof sloped at least 4 in. per 12 in., the roof clearance may be reduced to 3 ft.
- At 300 V or less between conductors, the clearance above only the roof overhang may be reduced to 18 in. where no more than 6 ft of conductors, 4 ft measured horizontally, pass over the overhang and they end at a through-the-roof raceway or approved support.
- The 3-ft clearance beyond the roof edge does not apply to the final span where the service drop or overhead service conductors attach to the side of the building.
- At 300 V or less between conductors, where the roof area is guarded or isolated, the roof clearance may be reduced to 3 ft.
Related sections
- NEC 225.19
- NEC 230.26
- NEC 230.28
- NEC 230.29
- NEC 680.9
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