Junction box in the basement ceiling
What's wrong here?
- The junction box has no cover over its splices
- Junction boxes are not permitted in an unfinished basement ceiling
- NM cable may not run along the side of a basement joist
- Nothing. This installation is compliant
Show the answer and the code reference
The answer
The junction box is left open with energized splices exposed; every box in a completed installation needs a cover.
Correct choice: 1. The junction box has no cover over its splices
314.25 requires each box in a completed installation to have a cover, faceplate, lampholder, or luminaire canopy, and 314.28(C) requires junction boxes to be provided with covers suited to the box. An open box leaves splices exposed to contact, lets a loosened wire connector fall out of the box, and gives an arc or a failed splice a path out of the enclosure into the wood framing above. In older Minnesota basements these open boxes are one of the most common things found on a remodel walkthrough.
How to fix it
Fold the splices into the box and install a 4-in. square blank cover held by the box's own machine screws. A steel cover screwed to the grounded steel box is grounded through that attachment, satisfying 314.28(C) and 250.110.
Code references
NEC 2023 314.25 — Covers and Canopies
In completed installations, each box shall have a cover, faceplate, lampholder, or luminaire canopy, except where the installation complies with 410.24(B).
Drills citing 314.25NEC 2023 314.28(C) — Covers
Pull boxes, junction boxes, and conduit bodies shall be provided with covers compatible with the box construction and suitable for the conditions of use; metal covers shall be grounded per 250.110.
Drills citing 314.28(C)
2026 NEC:same rule and number. 2026 NEC change summaries for Article 314 (new 314.2 listing, 314.16(B), 314.23, 314.27(B)) do not list 314.25 or 314.28(C); the cover requirement appears unchanged in rule and number. Not confirmed against the 2026 text. Confidence: low
Minnesota
Minnesota adopts the NEC by reference without amendment (Minn. Rules 1315.0200; Minn. Stat. 326B.35), so 314.25 and 314.28 apply as published. The 2023 NEC governs permits filed July 1, 2023 through Aug. 16, 2026; the 2026 NEC governs permits filed on or after Aug. 17, 2026 (exams moved to the 2026 NEC on Sept. 8, 2026). See the 2026 NEC note on this drill.
How Minnesota adopts the NECWhy the other choices are wrong
- Junction boxes are not permitted in an unfinished basement ceiling. A box in an unfinished basement is fully accessible, which is exactly what 314.29 asks for. Location is fine; the open top is the problem.
- NM cable may not run along the side of a basement joist. 334.15(C) limits cables run at angles to the joists; running parallel along the side of a joist and stapled is the normal method.
- Nothing. This installation is compliant. The work is described as finished, and a completed box with splices must be closed with a cover, faceplate, lampholder, or canopy.