NEC Minimum Vertical Clearances for Service Drops

A user asked the app for the NEC minimum vertical clearances for service drops. Section 230.24(B) of NEC 2023 sets four tiers based on what the conductors cross over, and 230.24(A) handles roofs separately. These numbers apply to overhead service conductors up to 600 volts; utilities on their side of the service point follow the NESC, which is usually similar or stricter.

The four ground clearance tiers

Ten feet applies at the electrical service entrance to buildings, at the lowest point of the drip loop, and above finished grade, sidewalks, and platforms accessible only to pedestrians, where the voltage does not exceed 150 volts to ground. Twelve feet covers residential property and driveways, and commercial areas not subject to truck traffic, for systems up to 300 volts to ground. That becomes fifteen feet when the voltage exceeds 300 volts to ground. Eighteen feet is required over public streets, alleys, roads, parking areas subject to truck traffic, and driveways on other than residential property. Measure at the lowest conductor sag point at the highest expected temperature, not at the attachment.

Roof clearances and the two famous exceptions

230.24(A) requires conductors passing over a roof to clear it by 8 feet, maintained for 3 feet in all directions from the roof edge. Two exceptions do most of the work in residential settings. Where the roof slope is 4 in 12 or steeper, the clearance drops to 3 feet. And where no more than 6 feet of conductor passes over no more than 4 feet of overhang, terminating at a through the roof raceway or approved support, the clearance can be as little as 18 inches. That 18 inch exception is the classic mast through the eave detail on most houses.

Related numbers worth keeping straight

The point of attachment itself must be at least 10 feet above grade per 230.26, and clearances from pools are separate and stricter under 680.9, which points to 22.5 feet over the water for utility style conductors. Communications drops have their own lower numbers, so do not let a cable company drop set your expectations for power. If a deck or addition is built under an existing drop, the clearance is measured from the new walking surface, which is how compliant services become violations without anyone touching the wiring.