Code Change Summary: A new exception permits Type NM and Type NMC cables to be installed without a 15-minute thermal barrier in specific non-habitable grade-level garages and storage buildings less than 1500 ft² of Type V construction.

SME commentary: In the 2026 NEC^®, Section 334.10 was revised to include a new exception to item (3), providing limited relief from the historical requirement that nonmetallic-sheathed (NM) and nonmetallic-sheathed corrosion-resistant (NMC) cables be installed behind a 15-minute thermal barrier in certain structures. The new exception recognizes that small, non-habitable grade-level storage garages and storage buildings present a substantially lower life-safety risk than habitable structures and therefore may safely omit the previously required 15-minute finish rating in Type V buildings.

Under prior editions of the Code, installers wiring storage garages or storage sheds were often required to cover exposed NM cable behind a 15-minute thermal barrier such as ½ inch gypsum board or a specific thickness of plywood. This requirement in 334.10(3) was intended to delay ignition or melting of the nonmetallic cable jacket during the early stages of a fire, allowing additional time for occupants to exit before the cables begin to melt and increase smoke density that can obscure visibility and hinder egress. While that protection is essential in habitable occupancies, applying it equally to small, nonhabitable garages and storage buildings imposed unnecessary cost and complexity with little improvement in safety.

The new 2026 exception allows NM and NMC cables to be used in non-habitable grade-level storage garages and storage buildings less than 1500 square feet with Type V construction “without a 15-minute thermal barrier”. This recognizes that such structures typically contain limited electrical wiring, minimal combustible finish materials, and provide direct, unobstructed egress through grade-level doors. Because these buildings are not designed for human occupancy, the risk of entrapment during a fire event is negligible.

When approving the change, the Code-Making Panel noted that nonhabitable storage buildings are comparable to other locations where NM cable is already permitted without a thermal barrier. Committee substantiation further clarified that the permitted buildings must be small, at grade level, and used solely for nonhabitable storage, ensuring that any fire scenario would not compromise a quick means of egress.

It is important to emphasize that the removal of the thermal-barrier requirement does not eliminate the obligation to protect cables from physical damage as required in 334.12(12), and 334.15. Installations may still employ open framing or unfinished interiors, but conductors must be securely fastened and protected where subject to damage. In practical terms, this change allows electricians to wire storage garages and storage buildings with NM cable in open stud cavities without the added cost of installing interior sheathing or thermal protection, while maintaining compliance with all other wiring method safeguards.

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 2026 NEC^® edition of NFPA 70.

2023 Code Language:

334.10 Uses Permitted. Type NM and Type NMC cables shall be permitted to be used in the following, except as prohibited in 334.12:

(3) Other structures permitted to be of Types III, IV, and V construction. Cables shall be concealed within walls, floors, or ceilings that provide a thermal barrier of material that has at least a 15-minute finish rating as identified in listings of fire-rated assemblies.

2026 Code Language:

334.10 Uses Permitted. Type NM and Type NMC cables shall be permitted to be used in the following, except as prohibited in 334.12:

(3) Other structures permitted to be of Types III, IV, and V construction. Cables shall be installed within walls, floors, or ceilings that provide a thermal barrier of material that has at least a 15-minute finish rating as identified in listings of fire-rated assemblies.

Exception to (3): Nonhabitable grade level storage garages and storage buildings less than 1500 ft² with Type V construction shall be permitted to have Type NM and Type NMC installed without a 15-minute thermal barrier.