Junction boxes must stay accessible

What the code requires

Boxes, conduit bodies and handhole enclosures must be installed so the wiring and devices inside them can be made accessible. For wiring methods, the NEC treats something as accessible when it can be removed or exposed without damaging the building structure or finish, and is not permanently closed in or blocked by the structure, other equipment, other building systems or the finish. A box sealed behind drywall, tile or cabinets does not meet that.

Underground boxes and handholes must be reachable without digging up sidewalks, paving, earth or other material that makes up the finished grade. A code exception covers certain listed boxes and handhole enclosures buried under gravel, light aggregate or noncohesive granulated soil, where their location is effectively described and they can be reached by excavation. That location description must be available to those authorized to access, maintain or inspect the wiring.

NFPA issued TIA 23-10 on March 21, 2023, effective April 10, 2023. For recessed boxes of 100 in³ or less, the opening in the finish must be centered within 1 in. of the box centerline and not extend past the box walls. A rectangular opening must be at least 2⅞ by 1¾ in., and a round one at least 3½ in. across. Larger boxes and conduit bodies need openings at least as large as their outer walls.

NFPA then issued TIA 23-18 on August 20, 2025, effective September 9, 2025. It rewrote the same subsection and replaced the TIA 23-10 wording. The opening sizes did not change, but the exception for smaller device openings no longer requires a nonmetallic box or nonmetallic cable or raceway. Confirm with your building department which wording it enforces.

On the job

• Junction boxes buried behind drywall, cabinets or tile are a standard inspection correction.
• TIA 23-10 allowed a reduced-size device opening only with a nonmetallic box and nonmetallic wiring. TIA 23-18, effective September 9, 2025, removed both limits, so metal boxes and metal wiring methods can now qualify if the other conditions are met. Ask your building department which version it enforces before relying on either.

Exceptions that matter

• Under TIA 23-18 (effective September 9, 2025), smaller openings around one or more devices are allowed when all four of these are met. Each device is fed by its own cable, or its own set of conductors in one raceway, entering from outside the box; those conductors are not spliced in the box or carried on to another device, and no other wiring enters the box. Each device comes out of the opening without damage; if removal needs a special tool, the circuit directory says where the tool is and gives a product or QR code for a replacement. All connections use the listed clamping-type connectors supplied with the device, arranged so they are exposed once the device is pulled out. The device assembly is listed for this use. The earlier TIA 23-10 also required a nonmetallic box and nonmetallic wiring.

What changed in 2023

In 2023 the in-building rule was extended to devices as well as wiring, and the underground exception now requires a description of the box location that is available to those who access, maintain or inspect the wiring.

In California

California did not approve an earlier TIA (20-19, on outdoor GFCI rules) as part of the 2022 California Electrical Code; local agencies needed a local ordinance or an alternative-method approval to enforce it. Whether TIAs 23-10 and 23-18 apply under the 2025 code is not confirmed; check with your building department.

Related sections

• NEC 314.30
• NEC 314.20: Setting boxes flush with the wall surface
• NEC 314.21

Where this comes from

• Mike Holt: Understanding the 2023 NEC, Vol. 1, 314.29
• NFPA TIA 23-10 (Log 1690), hosted by NYC Department of Buildings
• Kentucky DHBC: July 15 2026 NEC Update (list of 2023 NEC TIAs)
• California Building Standards Commission: Bulletin 23-01
• Read the official NEC free at NFPA