UF-B Wire

Q: Can UF-B be buried without conduit?

Yes — UF-B is approved for direct burial per NEC 340.10. Minimum burial depth depends on the circuit voltage and whether GFCI protection is provided: 24 inches for 120V non-GFCI, 18 inches for 120V with GFCI, and 12 inches under a 4-inch concrete pad. See our burial depth guide for the complete table.

Q: What is the difference between UF-B and NM-B?

UF-B has a solid PVC jacket molded around the conductors, making it waterproof and suitable for underground burial. NM-B has a loose paper-wrapped jacket that is not water-resistant. UF-B can be used anywhere NM-B can, plus wet locations and underground. UF-B is harder to strip because the jacket is bonded to the conductors.

NEC Quick Answer

UF-B cable ampacity is determined using the 60C column of NEC Table 310.16, same as NM-B. The individual conductors within UF-B have 90C-rated insulation, which can be used as a starting point for derating calculations per NEC 340.80. The cable itself is rated for wet, dry, and direct burial locations.

NEC 2023: Table 310.16, Section 340.80

UF-B stands for Underground Feeder Cable. Direct burial outdoor circuits. Similar to NM-B but moisture-proof. Ampacity limited to 60°C column.

Dry rating60°C

Wet rating60°C

Voltage600V

Locationsdry, damp, wet, direct burial

Specifications

Property	Value
Full name	Underground Feeder Cable
Insulation material	PVC integral with jacket (solid)
Outer covering	Integral moisture-resistant PVC
Temperature rating (dry)	60°C (140°F)
Temperature rating (wet)	60°C (140°F)
Voltage rating	600V
Approved locations	dry, damp, wet, direct burial

Ampacity by gauge

The table below shows NEC Table 310.16 ampacity for UF-B conductors. Values shown reflect the 110.14(C) termination temperature limit, which determines the real-world usable ampacity - not just the insulation rating. Click any gauge to see the full derating chain.

Gauge	Copper	Aluminum
14 AWG	See page	-
12 AWG	See page	-
10 AWG	See page	-
8 AWG	See page	-
6 AWG	See page	-
4 AWG	-	-
3 AWG	-	-
2 AWG	-	-
1 AWG	-	-
1/0 AWG	-	-
2/0 AWG	-	-
3/0 AWG	-	-
4/0 AWG	-	-

When to use UF-B wire

Direct burial outdoor circuits. Similar to NM-B but moisture-proof. Ampacity limited to 60°C column.

Choose UF-B when:

You need direct burial without conduit to an outbuilding, landscape light, or post lamp
The run is underground and you want to avoid the cost of conduit installation
You're feeding a detached shed or garage with a short underground run

Don't use UF-B when:

Inside conduit in hot locations - the solid jacket doesn't dissipate heat well in enclosed spaces
Long runs requiring large wire - UF-B maxes out at practical sizes; switch to THHN in conduit
Where you need to strip the jacket frequently - UF-B's bonded jacket is notoriously difficult to strip

Common applications for UF-B:

Direct burial underground - approved for direct burial without conduit per NEC 300.5
Outbuilding and shed feeds - the standard cable for underground runs to detached structures
Outdoor lighting circuits - permitted for direct burial to landscape lighting posts
Not permitted in conduit in some jurisdictions - check local amendments; PVC jacket doesn't dissipate heat well in enclosed spaces

NEC code references for UF-B

The NEC defines wire insulation types in Table 310.4(1) (formerly Table 310.104(A)). Key sections that apply:

Table 310.4(1) - lists UF-B with its temperature rating, insulation material, and approved locations
Table 310.16 - ampacity values for conductors in raceway, cable, or earth (the values shown in our ampacity table above)
Section 110.14(C) - termination temperature limits that determine real-world usable ampacity
Section 310.15(C)(1) - adjustment factors for more than 3 current-carrying conductors in a raceway

Frequently asked questions about UF-B wire

Can UF-B be buried without conduit?

Yes - UF-B is approved for direct burial per NEC 340.10. Minimum burial depth depends on the circuit voltage and whether GFCI protection is provided: 24 inches for 120V non-GFCI, 18 inches for 120V with GFCI, and 12 inches under a 4-inch concrete pad. See our burial depth guide for the complete table.

What is the difference between UF-B and NM-B?

UF-B has a solid PVC jacket molded around the conductors, making it waterproof and suitable for underground burial. NM-B has a loose paper-wrapped jacket that is not water-resistant. UF-B can be used anywhere NM-B can, plus wet locations and underground. UF-B is harder to strip because the jacket is bonded to the conductors.

Other wire insulation types

THHN 90°C THWN 75°C THWN-2 90°C XHHW 90°C XHHW-2 90°C RHH 90°C RHW-2 90°C USE-2TW 60°C NM-B 60°C MC Cable 90°C AC Cable (BX) 90°C SER/SEU 75°C PV Wire 90°C THHW 90°C THW 75°C THW-2 90°C RHW 75°C MI 90°C UF 60°C XHH 90°C FEP 90°C SIS 90°C

Requirements vary by state. NEC edition, licensing, permits, and GFCI rules differ by jurisdiction. Check your state or pick it below for personalized info across WireRef.

Important: For reference only. Not a substitute for a licensed electrician. Electrical work can cause serious injury, death, fire, or property damage if performed incorrectly. Always hire a licensed electrician for electrical work, especially for service upgrades, panel work, and 240V circuits. Values are derived from NFPA 70 (NEC) for educational purposes. Always verify against your locally adopted NEC edition and amendments - local jurisdictions may enforce stricter requirements. WireRef provides reference information only and is not responsible for work performed based on this content. NEC® is a registered trademark of the National Fire Protection Association. Free NEC access via NFPA · OSHA Electrical Safety · Terms of use.

NEC 2023 references verified April 2026