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What is the minimum clearance of overhead electric service drop wires above a house roof?
Saturday, June 30, 2018
The National Electric Code (NEC 230.24(A)) requires that overhead service wires (conductors) be a minimum of 8 feet above a roof, including for a minimum 3 feet in all directions from the edge of the roof, but then provides four allowable exceptions. One of the exceptions is the most common type of residential overhead electric service type, so we will start with it. If the service mast is a “through-the-roof” installation, meaning that it only penetrates the roof at the overhang to come down to a meter at the exterior wall below, as in the photo above, then the wires are only required to clear the roof by 18 inches.
There are a couple of further stipulations for this exception to be allowed:
- The mast must be located within 4 feet of the edge of the roof, so maximum roof overhang is 4 feet.
- Not more than 6 feet of service wires are allowed to pass over the roof. This is intended to avoid an installation with wires that run diagonally across the roof overhang near the edge for an extended distance at the low 18-inch height.
The second exception allows a reduction to 3 feet above the roof when the roof pitch is 4/12 (4 inches of rise for every 12 inches of horizontal run) or more. There are no restrictions on the length of service conductors over the roof. The logic behind this exception is that steeply sloped roofs are not likely be be walked on by anyone except workers on the roof.
Exemption number three allows service conductors attached to the side of a building below roof level to be exempt from “8 foot clearance up to 3 feet from edge of roof” rule to enable attachment to the structure.
The final exception in the NEC states that areas above roof surfaces that are subject to vehicular or pedestrian traffic must meet the same standards for service conductor clearance above the ground for the particular type of traffic, as outlined in NEC 230.24(B). This is an unusual scenario for residential construction, and would actually increase the clearance requirements when there is vehicular traffic.
For an overview of the clearance requirements between utility pole and house, see our blog post What is the minimum overhead electric service drop height/clearance to a house? And for swimming pool minimums, see our blog post What are the clearance requirements for an overhead electric service drop that is directly over or near a swimming pool? Also, What is the electrical "service point" of a house?
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