Flush-mounted fixtures require a shade to hide their bulbs.
The International Residential Code, on which most local and building codes are based, specifies lighting requirements for the interior of a residence, such as the number of switches and lighting outlets. However, it does not specify the type of lighting fixture needed to fulfill those requirements. Such choices, including flush-mounted fixtures, are left entirely to homeowners and electricians.
Types
There are three main types of lighting fixtures. First are hanging fixtures. They take up the most room but can cast the brightest light because only room dimensions and esthetics limit the number of their bulbs. They can be powered directly from a junction box behind the ceiling or hang from the ceiling and plugged into a wall outlet. Second are recessed fixtures. Their bulbs disappear into lighting cans installed behind the ceiling. They take up the least amount of room, making them useful for low-ceiling applications or modern decor.
Flush-Mounted Fixtures
The third type of lighting fixtures are flush-mounted fixtures. They require junction boxes behind the ceiling but expose the bulbs and fixture attachments below the ceiling. The International Residential Code mandates that the boxes enclosing flush-mounted devices must be completely enclosed at the back and all sides, and must be strong enough to provide support for the device. However, the screws for supporting the box cannot be used to attach the device itself. The boxes enclosing any type of light fixture, including flush-mounted versions, must be deep enough to allow correct mounting without damage to the conductors within the box.
Depth
Box depth can depend on the gauge of conductor for the fixture. Gauge is defined by the American Wire Gauge system, which commonly is used throughout the United States, uses smaller numbers to represent larger wires. Conductors at 8, 6 or 4 AWG need boxes with an internal depth of at least 2.06 inches. Conductors at 10 or 12 AWG need an internal depth of at least 1.18 inches. However, if the equipment projects rearward from the mounting plane of the box by more than 1 inch, then the depth must equal that of the equipment plus at least 0.25 inches. Conductors at 14 AWG or smaller require a depth of at least 0.93 inches.
Shades
Shades for flush-mounted fixtures come in a bewildering array of shapes, sizes, colors and styles. Almost all are made of translucent glass to allow light exposure while hiding the actual bulbs. The most common material for holding the shade to the ceiling and trimming the joint between the shade and its surface is metal. The construction of most flush-mounted fixtures allows the average homeowner to easily change the bulb by removing the shade and reattaching it. Installing such fixtures in new locations, however, may require the expertise of professionals.
Tags: least inches, behind ceiling, depth least, depth least inches, flush-mounted fixtures, boxes enclosing