Which type of installation does not require additional support for nonmetallic sheathed cable?

For nonmetallic sheathed cable, the installation type that does not require additional support is in attics without stairs. This is because the National Electrical Code (NEC) specifies that nonmetallic sheathed cable can be run in attics where they are not subject to physical damage and if those areas are not accessible. In attics without stairs, the cables are typically considered safe from potential stresses or hazards that might require additional support.

In contrast, other installation types listed would generally require additional support. For instance, in wet locations, cables must be protected against moisture, which can necessitate different supports or enclosures to ensure safety and durability. Similarly, residential buildings typically have specific support requirements to ensure that the cable is properly secured as it transitions through areas that could be accessed or damaged. Basements, due to their propensity for moisture and varying temperature conditions, may also invoke further support requirements to manage these environmental factors safely.