Romex wiring is a brand name for electrical cabling that is covered with a non-metallic sheath and used in residential branch wiring. It is commonly found in lighting and electrical outlets in homes. Because it is protected by non-metallic sheathing, it may be used in damp environments such as basements.
Under the National Electrical Code, Romex wiring is not permitted in commercial buildings or residential structures taller than three stories. Romex cabling is less flexible than other forms of cabling, and special rules apply to its use. It must be permanently clamped to a junction box and secured at periodic intervals to prevent sagging.
Supporting materials that can damage the sheathing, such as staples and nails, may not be used to support it. It is intended for permanent wiring installations and should not be used for extension cords.