334.10(2) Uses Permitted.

Type NM and Type NMC cables are now permitted to be used in detached garages of multifamily dwellings permitted to be of Types III, IV, and V construction.
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Type NM and Type NMC cables are now permitted to be used in detached garages of multifamily dwellings permitted to be of Types III, IV, and V construction.

Code Change Summary: A new use permitted for Type NM and Type NMC cables.

In the 2023 NEC®, Type NM and Type NMC cables are now permitted to be used in detached garages of multifamily dwellings permitted to be of Types III, IV, and V construction.

For years, Nonmetallic Sheathed Cables covered in NEC® Article 334 have been permitted to be used in one- and two-family dwellings and their garages, and in multi-family dwellings permitted to be of Types III, IV, and V construction, but not in any detached garages of multifamily dwellings.

The occupancy classification and construction type of a building will dictate the wiring methods permitted to be used. If the building is an assembly occupancy for example, then wiring methods and rules in NEC® Article 518 will apply. If the building is type I or II construction, then nonmetallic sheathed cable is not permitted unless installed in a raceway type that is acceptable for types I or II construction in accordance with the NEC®.

There are several construction types covered in the International Building Code (IBC). IBC chapter 6 classifies the five different construction types most used for buildings.

Types I and II construction are those types of construction in which the building elements specified in IBC Table 601 are of noncombustible materials, except as permitted in IBC Section 603 and elsewhere in the IBC.

Type III construction is a type of construction in which the exterior walls are of noncombustible materials and the interior building elements are of any material permitted by this code.

Type IV construction is a type of construction in which the building elements are mass timber or noncombustible materials and have fire-resistance ratings in accordance with IBC Table 601.

Type V construction is a type of construction in which the structural elements, exterior walls and interior walls are of any materials permitted by the IBC. Type V construction is the most common construction type for residential dwellings including single family and multi-family dwelling type occupancies.

Keep in mind that some detached garages may be “permitted” to be of Types III, IV, or V construction by the IBC but the architect may choose to build the detached garages with noncombustible materials typically seen in Types I and II construction. NM cables could still be used when this occurs since the detached garage is “permitted” to be construction Type III, IV, or V, even if it was actually constructed as a Type I or II.

Below is a preview of the NEC®. See the actual NEC® text at NFPA.ORG for the complete code section. Once there, click on their link to free access to the 2023 NEC® edition of NFPA 70.

2020 Code Language:

334.10 Uses Permitted.

(2) Multi-family dwellings permitted to be of Types III, IV, and V construction.

2023 Code Language:

334.10 Uses Permitted.

(2) Multi-family dwellings and their detached garages permitted to be of Types III, IV, and V construction.

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334.10(2) Uses Permitted.

Below is a Real Question from our Electrical Continuing Education Courses for Electrical License Renewal:

Based on the 2023 NEC, which of the following is true?

A: Only Type NMC cable can be used in a detached garage.
B: Only Type NM cable can be used in a detached garage.
C: Type NMC cable must be used in all garages.
D: Type NM and Type NMC cables are now permitted to be used in detached garages of multifamily dwellings permitted to be of Types III, IV, and V construction.
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