What Is UF-B Wire?
UF-B stands for underground feeder cable, type UF, and it is built for direct burial in soil without conduit. Unlike standard NM-B Romex, which is rated only for dry indoor use, UF-B has a solid jacket molded tightly around the conductors to resist moisture and sunlight. That construction lets you bury it directly in a trench, which makes it the go-to cable for outdoor branch circuits.
What UF-B Is Used For
UF-B is the standard choice for running power to detached garages and sheds, outdoor receptacles on posts, well pumps and pond pumps, landscape and security lighting, and other 120-volt and 240-volt outdoor circuits. It carries the same conductor sizing as NM-B, so 14/2 UF-B is rated for 15 amps and 12/2 UF-B is rated for 20 amps under the 60 degrees Celsius column.
Burial Depth Requirements
Burial depth is set by NEC Table 300.5 and measured from the top of the cable to finished grade.
24 Inches: Standard Direct Burial
Direct-buried UF-B in open soil requires a minimum of 24 inches of cover. This is the most common residential requirement for a buried branch circuit.
18 Inches: Conduit or Driveway
Running UF-B inside PVC conduit, or burying under a one-family or two-family dwelling driveway, allows a reduced depth of 18 inches.
12 Inches: GFCI-Protected Residential Branch
A 120-volt residential branch circuit rated 20 amps or less, protected by GFCI for the entire circuit, may be buried at 12 inches. This is common for backyard outlets and lighting.
UF-B vs NM-B Romex
NM-B Romex is for dry interior locations only and must never be buried or run outdoors exposed. UF-B handles moisture, soil, and sunlight. If your run leaves a dry indoor space and goes underground or outside, UF-B is the correct cable.
Installation Tips and Safety
Call 811 before you dig to mark existing utility lines. Outdoor circuits require GFCI protection. Add a bedding layer of clean sand under the cable to protect it from rocks, and place underground warning tape above the trench. Where the cable rises out of the ground it must be protected from physical damage per NEC 300.5. Follow the National Electrical Code and local amendments, confirm with your authority having jurisdiction, and use a licensed electrician for outdoor feeders and any work at the panel.
IB Lighting stocks Southwire 12/2 and 14/2 UF-B in our electrical wire and cable collection, with free freight plus free freight insurance on every order. Call (800) 674-9019 for help planning an outdoor run.