How To Look At A House

McGarry and Madsen's home inspection blog for buyers of  

site-built, mobile/manfuactured and modular homes

What is the minimum overhead electric service drop height/clearance to a house?

Saturday, December 22, 2018

The National Electrical Code (NEC) has multiple different minimum standards, all of which depend on what is under the wires as they run from the utility pole to the service mast on your house. Thanks to Code Check, we have an excellent graphic to make things clear. Their long-time illustrator, Paddy Morrissey, loves to sneak images of Ben Franklin and his famous kite-in-a-thunderstorm experiment into their electrical diagrams, as you will notice. 

Starting with the most common ones:

  • Over residential property and driveways on the property (E) - 12 feet
  • Over walking surfaces that are only accessible to pedestrians (D) - 10 feet
  • Over a roadway (F) - 18 feet 
  • Over a roof low-slope roof, with less than 4/12 slope (A) - 8 feet
  • Over a roof with 4/12 slope or more (B) - 3 feet
  • Over a roof with 4/12 slope or more, within 4 feet of roof edge at eaves (C) - 18 inches
  • Above decks and balconies, including out 3 feet (G,H) - 10 feet
  • To the sides and below an openable window (I) - 3 feet

    We recently got an education in the difference between the 12-foot and 10-foot clearance requirements for residential property from Jerry Peck, a retired building inspector and code consultant. The overhead service drop shown below, to a 1940s bungalow in Gainesville, was over parking spaces that had been added because the house had become a student rental, and had a 10-foot clearance at its lowest point. 

    We were not sure whether a parking space would qualify as a driveway for a 12-foot clearance or not. Jerry quoted NEC to make the point that ALL residential property, except areas that are ONLY accessible to pedestrians (which usually means behind a fence or other vehicular obstacle), must comply with the 12-foot rule. Even before the parking was added, it was not in compliance.

    The local electric utility may have different standards, which would override the NEC code. For the clearance requirements over a swimming pool, see our blog post What are the clearance requirements for an overhead electric service drop that is directly over or near a swimming pool? And for a more detailed exploration of the requirements as the service wires cross above a roof, see our blog post What is the minimum clearance of overhead electric service drop wires above a house roof?

    And by the way, if anyone is paying attention, the service mast shown at the top of the page is a 4-wire for three-phase service, which is possible, but rarely seen in residential construction. Also, it’s not necessary look up any code standards to know that the service drop shown below is wrong.

• • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • 

    Here’s links with answers to some Frequently Asked Questions (FAQ) about ELECTRICAL SERVICE:

What is the minimum overhead electric service drop height/clearance to a house?

 Why is a leaning electrical service mast dangerous? 

• What is the fireman’s switch emergency disconnect requirement for residential electrical service?

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

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

What is three phase electric service?

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

What does it mean when I find buried yellow "CAUTION" tape when digging a hole in the yard?

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

What is the difference between the electric service to a mobile home and a site built home? 

• What is the minimum size electric service to a mobile/manufactured home?

• Can anything else be attached to a service mast for overhead electric service besides the service cables? 

• What is the electrical "service point" of a house? 

Why is there a 3-phase breaker in a single phase panel with only two bus bars?

What is a service conductor?

• What is the difference between single-phase and three-phase electric service? 

• What is the minimum clearance under an electrical service drip loop of a house? 

     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.

Illustrations by Code Check.




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