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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:

  1. The mast must be located within 4 feet of the edge of the roof, so maximum roof overhang is 4 feet.
  2. 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?  Also, What is the electrical "service point" of a house?

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Here’s links to a collection of our other blog posts about ELECTRICAL WIRING:

Which house appliances need a dedicated electrical circuit?

Can a short circuit cause a high electric bill?

Can you use a light switch for a water heater disconnect? 

• When did the requirement for two 20-amp kitchen counter appliance circuits begin?

What is the maximum spacing requirement for securing NM-cable (nonmetallic-sheathed cable)?

Is it alright to just put wire nuts on the end of unused or abandoned NM-cable or wiring?

What causes copper wires to turn green or black in an electric panel?  

 Is the latest edition of the National Electrical Code (NEC) the standard used for the electrical system of new homes?

What are typical aluminum service entrance wire/cable sizes for the electrical service to a house?

Why is it unsafe to bond neutral and ground wiring at subpanels?

When was it first required that neutrals and grounds be separated (not bonded) on any panel past the main service panel? 

What is the difference between a UL rating for dry, damp, and wet locations? 

What is three phase electric service?

What is a reliable way to tell if the electrical service is 3 phase or single phase? 

Can NM-cable (Romex®) be used to make a cord and plug to connect an appliance?

What are the requirements for NM-cables entering an electric panel box?

What is the color code for NM cable (Romex®) sheathing?

Can I remove a 240-volt range receptacle and hard-wire the range? 

Why do some wires in an electric panel have tape wrapped around them near their connections?

Why is undersize electric wiring in a house dangerous? 

Why is bundled wiring in an electric panel a defect?

What causes flickering or blinking lights in a house?

What is the voltage rating of a house electrical system? 

Why are old electrical components not always "grandfathered" as acceptable by home inspectors?

What is tinned copper wiring?

What is a conduit body or condulet? 

How can I find out the size of the electric service to a house?

What could cause an extremely high electric bill?

Do any pre-1960 houses have aluminum wiring?

What is the gooey stuff on some of the wire connections in the electric panel? 

How much does it cost to rewire a house?  

What is an "open junction box"? 

What are the clearance requirements for an overhead electric service drop that is directly over or near a swimming pool? 

How dangerous is old electrical wiring? 

What is a ground wire? 

What are the most common homeowner electrical wiring mistakes?

I heard that aluminum wiring is bad. How do you check for aluminum wiring? 

What is "knob and tube" wiring? 

    Visit our ELECTRICAL page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.

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