314.20 Flush-Mounted Installations.

The box on the left cannot be recessed more than ¼ inch. The box on the right must be flush or have an extension ring installed to ensure that there are no exposed combustible materials behind the luminaire (not shown).
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The box on the left cannot be recessed more than ¼ inch. The box on the right must be flush or have an extension ring installed to ensure that there are no exposed combustible materials behind the luminaire (not shown).

Code Change Summary: Changes were made to provide clarity for flush-mounted box installations.

The previous 2014 code language in Section 314.20 provided rules for installing a box inside a wall or ceiling. Well, what about a column? Is a column or a post considered a wall? How about a floating architectural drop above an office area? Is it considered a ceiling or just an architectural feature?

Now, Section 314.20 applies to “flush-mounted installations” to be more politically correct. This correction aligns with a similar code change that occurred in the 2014 NEC to Section 314.27(A)(1) which was changed from “wall outlets” to “vertical surface outlets”.

Below is a preview of Article 314. See the actual NEC text at NFPA.ORG for the complete code section. Once there, click on their link to free access to the 2017 NEC edition of NFPA 70.

2014 Code Language:

314.20 In Wall or Ceiling. In walls or ceilings with a surface of concrete, tile, gypsum, plaster, or other noncombustible material, boxes employing a flush-type cover or faceplate shall be installed so that the front edge of the box, plaster ring, extension ring, or listed extender will not be set back of the finished surface more than 6 mm (1⁄4 in.).

In walls and ceilings constructed of wood or other combustible surface material, boxes, plaster rings, extension rings, or listed extenders shall be flush with the finished surface or project therefrom.

2017 Code Language:

314.20 Flush-Mounted Installations. Installations within or behind a surface of concrete, tile, gypsum, plaster, or other noncombustible material, including boxes employing a flush-type cover or faceplate, shall be made so that the front edge of the box, plaster ring, extension ring, or listed extender will not be set back of the finished surface more than 6 mm (1∕4 in.).

Installations within a surface of wood or other combustible surface material, boxes, plaster rings, extension rings, or listed extenders shall extend to the finished surface or project therefrom.

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314.20 Flush-Mounted Installations.

Below is a Real Question from our Electrical Continuing Education Courses for Electrical License Renewal:

Which of the following is true for a receptacle box recessed into a wall covered by gypsum sheetrock?

A: The front edge of the box shall be set back from the finished surface at least 1∕4 inch.
B: The plaster ring shall be set back from the finished surface at least 1∕4 inch.
C: The front edge of the box, plaster ring, extension ring, or listed extender shall not be set back of the finished surface more than 1∕4 inch.
D: The front edge of the box must be flush with the finished surface.
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