There are two types of outlet covers used on external outlets. The first type is for damp locations that covers the outlet when it's not in use:

Damp cover

And the second type is for wet locations that allow the outlet to be sealed while in use:

Wet in-use cover

How is wet vs damp defined by NEC to differentiate when one cover is required over another?

NEC 406.8 Receptacles in Damp or Wet Locations: "A receptacle installed outdoors in a location protected from the weather or in other damp locations shall have an enclosure for the receptacle that is weatherproof when the receptacle is covered (attachment plug cap not inserted and receptacle covers closed).". And "receptacles installed in a wet location shall have an enclosure that is weatherproof whether or not the attachment plug cap is inserted."

2 Answers 2


NEC 2008

406.8 Receptacles in Damp or Wet Locations.
(A) Damp Locations. ... A receptacle shall be considered to be in a location protected from the weather where located under roofed open porches, canopies, marquees, and the like, and will not be subjected to a beating rain or water runoff. All 15- and 20-ampere, 125- and 250-volt nonlocking receptacles shall be a listed weather-resistant type.

NEC 2008

Article 100 Definitions

Location, Damp. Locations protected from weather and not subject to saturation with water or other liquids but subject to moderate degrees of moisture. Examples of such locations include partially protected locations under canopies, marquees, roofed open porches, and like locations, and interior locations subject to moderate degrees of moisture, such as some basements, some barns, and some coldstorage warehouses.

Location, Dry. A location not normally subject to dampness or wetness. A location classified as dry may be temporarily subject to dampness or wetness, as in the case of a building under construction.

Location, Wet. Installations underground or in concrete slabs or masonry in direct contact with the earth; in locations subject to saturation with water or other liquids, such as vehicle washing areas; and in unprotected locations exposed to weather.

  • Thanks Tester. We need to rename you to NEC Lookup Guy. :)
    – BMitch
    Jun 25, 2012 at 15:25
  • @BMitch You got to know the rules, if you want to play the game.
    – Tester101
    Jun 25, 2012 at 15:26
  • 2
    When in doubt use "In-use" covers.
    – Tester101
    Jun 25, 2012 at 15:33
  • 1
    Ignorance is bliss. I was much happier before I discovered the wire was live.
    – BMitch
    Jun 25, 2012 at 15:42
  • 2
    Seconding the "always use an in-use cover" advice. Someone will eventually leave an extension cord or Christmas lights plugged in. If not you, then the next person to live there. Oct 2, 2012 at 18:57

If there is nothing plugged in more than 3 hiours(continious use) a regular weather proof cover is fine for a damp location, bubble covers break off.

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