Before a residential electrical rough-in inspection, check cable protection and support, conductor length, box size and placement, grounding, and the required outlet layout. This study checklist uses the City of St. Paul’s 2020 NEC rough-in checklist as a starting point. Confirm your local inspection requirements and adopted code before covering the work.
Watch JCR explain the rough-in wiring methods
Victor’s Chapter 3 overview shows where to find the rules for conductors, cables, boxes and raceways. Use those article locations as you work through this checklist.
Watch JCR explain the rough-in wiring methodsWatch the existing JCR lesson on YouTube1. Protect cable from nails and screws
For NM cable through bored holes in wood framing, 300.4(A)(1) requires at least 1¼ inches from the hole’s edge to the nearest edge of the wood member, or the required protective plate or bushing. The normal steel-plate minimum is 1/16 inch. A thinner plate must be listed and marked for equivalent protection.
Measure from the hole’s edge, not its center. Structural drilling limits are a separate building-code check.
2. Secure and support NM cable
Under 334.30, the usual limits are 4½ feet between supports and within 12 inches of a cable entry into a box, cabinet or fitting. Use fasteners that do not damage the cable.
The 314.17(B)(2) Exception applies only to NM cable in a single-gang nonmetallic box no larger than 2¼ × 4 inches, mounted in a wall or ceiling. The cable does not have to be secured to the box if it is fastened within 8 inches of the box, measured along the sheath. The sheath must also extend at least ¼ inch through the knockout.
Prepare for NEC installation questions
Turn lessons like this into test-day skills. Find the rule, work the calculation and practice with JCR’s mock exam questions.
Live classes teach the 2020 NEC. Check your state’s exam requirements before choosing a course. NC prep includes NC business and law. For another state, also study any business-and-law material required for your license. Need the code book? JCR carries the 2020 NEC softbound book.
Already licensed? Earn your CE with JCR
Choose in-person classes, live Zoom or recorded courses. Review NEC navigation, grounding and bonding, and other electrical topics. Check the course’s NEC edition, state approval and credit hours before enrolling.
See CE courses and class dates3. Leave enough conductor at each box
Leave at least 6 inches of free conductor for splices and terminations under 300.14, measured from where it emerges from the raceway or cable sheath. If the box opening is less than 8 inches in any dimension, leave enough to extend at least 3 inches outside the opening. These measurements describe different starting points.
4. Check box fill and the finished wall surface
Calculate box fill under 314.16, including the applicable allowances for conductors, grounds, clamps and devices. Do not judge capacity by whether you can force everything inside. Use our worked box-fill example.
For the wall and ceiling installations covered by 314.20, a box in a noncombustible surface may be set back no more than ¼ inch. At a combustible surface, it must be flush with or project from the finished surface. Account for the finish thickness while placing boxes.
5. Make up the equipment grounding connections
Check the continuity and required connections under 250.148. Bond metal boxes where required, and arrange connections so removing a device does not interrupt equipment-grounding continuity. See our EGC guide.
6. Check circuits and outlet locations
Review required circuits and receptacles room by room under Article 210. Confirm the planned GFCI protection and AFCI protection. Living-room walls, kitchen countertops, bathrooms and garages do not all use the same layout rules.
Practice question
A small outlet box has 6 inches of free conductor for a receptacle connection, measured from the cable sheath, but only 2 inches extends outside the opening. Does that meet 300.14?
No. If the opening is less than 8 inches in any dimension, the conductor must also extend at least 3 inches outside it. Meeting one measurement does not remove the other.
Common questions
Should drywall go up before the rough-in inspection?
Arrange the inspection before covering work that the inspector needs to see. Your local permitting office sets the required inspection stages and readiness conditions.
Does this checklist cover every requirement?
No. It covers common residential rough-in checks. The installation may also need load calculations, special equipment circuits, firestopping or other checks. Read the applicable articles and local requirements.
How should I study rough-in questions?
Sort each question by its subject: protection in Article 300, boxes in 314, NM cable in 334, grounding in 250, or branch circuits in 210. Our wiring-method numbering guide helps you find the right section faster.
Keep practicing
Try our most-missed NEC mock exam questions and 2020 NEC practice questions. Find the rule for each answer, work the calculation, and repeat the questions you miss.
Prepared October 25, 2026, for the 2020 NEC. Use the edition required by your licensing exam. On the job, use the locally adopted code and amendments.
