Where NM cable (Romex) is allowed
NM cable, often called Romex, is allowed in one- and two-family homes and their garages. In other buildings, it depends on construction type: Types III, IV and V allow it with limits, and Types I and II only inside raceways.
What the code requires
Except where 334.12 prohibits it, NM and NMC cable may be used in one- and two-family homes, including their attached or detached garages and their storage buildings. It may also be used in multifamily dwellings permitted to be of Types III, IV or V construction and, since 2023, in their detached garages.
In other structures permitted to be of Types III, IV or V construction, NM cable is allowed only when concealed in walls, floors or ceilings that provide a thermal barrier with at least a 15-minute finish rating. It is also allowed in cable trays in those structures if the cable is identified for that use.
In buildings of Types I and II construction, NM cable may be used only inside raceways that are permitted in those building types.
On the job
- On commercial tenant improvements, NM cable needs a building permitted to be Type III, IV or V construction, concealment behind a 15-minute finish, and a space that 334.12 does not exclude. In Types I and II construction, it must be in a raceway.
- The construction type should be confirmed from the building plans, not guessed.
What changed in 2023
The 2023 NEC added the detached garages of multifamily buildings to the places NM cable is allowed.
In California
California's 2025 code adds a note, for housing regulated by HCD, that construction Types I through V in this section are as defined in the California Building Code.
Related sections
- NEC 334.12: Where NM cable (Romex) is not allowed
- NEC 334.15: Protecting exposed NM cable
- NEC 334.30: Stapling and supporting NM cable
Where this comes from
- California Building Standards Commission: 2025 California Electrical Code amendments (Title 24, Part 3)
- NFPA: 2026 NEC Second Draft, CMP-6 (shows 2023 text of 334.10)
- ExpertCE: How have 2023 NEC updates changed NM and NMC cable installation rules
- Mike Holt: Summary of the 2023 NEC changes
- Read the official NEC free at NFPA
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