Bath fan feed in the attic
What's wrong here?
- The cable crosses the chord tops near the scuttle with no guard strips
- NM cable may not be laid in or in contact with attic thermal insulation
- All NM cable run in an attic must be installed in conduit or tubing
- Nothing. This installation is compliant
Show the answer and the code reference
The answer
The cable is laid across the tops of the bottom chords right next to the scuttle opening with no guard strips.
Correct choice: 1. The cable crosses the chord tops near the scuttle with no guard strips
In accessible attics, NM cable is installed per 320.23 (334.23). Cable run across the tops of floor joists or bottom chords must be protected by guard strips at least as high as the cable; where the attic is reached only through a scuttle (no permanent stairs or ladder), that protection is required only within 6 ft of the nearest edge of the scuttle or attic entrance (320.23(A)). Anyone coming through the hatch kneels and crawls across those chords, and stored boxes and insulation crews end up on the cable too. Beyond 6 ft from the hatch, the same run would be acceptable.
How to fix it
Within 6 ft of the scuttle, nail guard strips at least as tall as the cable along both sides of it, or reroute the cable along the side of a chord at least 1-1/4 in from the edges (320.23(B), 300.4(D)). Do not bore or notch truss chords to get the cable out of the way; trusses may not be altered without the truss designer's approval.
Code references
NEC 2023 320.23(A) — Cables Run Across the Top of Floor Joists
Where run across the top of floor joists, or within 2.1 m (7 ft) of the floor or floor joists across the face of rafters or studding, in accessible attics the cable shall be protected by guard strips at least as high as the cable. Where the space is not accessible by permanent stairs or ladders, protection is required only within 1.8 m (6 ft) of the nearest edge of the scuttle hole or attic entrance.
Drills citing 320.23(A)NEC 2023 334.23 — In Accessible Attics
The installation of NM cable in accessible attics or roof spaces shall comply with 320.23.
Drills citing 334.23
2026 NEC:same rule and number. Two searches turned up no 2026 change to the attic guard-strip rule in 320.23(A) or to the 334.23 cross-reference. The 2026 Article 320/334 changes reported (listed support hardware in .2 and .30) don't touch this rule. No source confirmed the text against 2026 itself, so treat this as unconfirmed. Confidence: low
Minnesota
Minnesota adopts the NEC by reference without amendment (Minn. Rules 1315.0200; Minn. 326B.35), so 320.23(A) applies 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
- NM cable may not be laid in or in contact with attic thermal insulation. NM is routinely installed in insulated walls and attics; 334.80 already holds it to 60 C ampacity and requires further adjustment only where more than two cables are bundled in contact with insulation.
- All NM cable run in an attic must be installed in conduit or tubing. NM is permitted in attics of dwellings; protection is required only where it is exposed to damage, such as across joists near the access (320.23(A)).
- Nothing. This installation is compliant. Anyone crawling through the hatch puts knees and hands right where the cable crosses the chords; 320.23(A) requires guard strips there.