For NM cable through a bored hole in wood framing, keep the hole’s edge at least 1¼ inches from the nearest edge of the wood member. When that setback cannot be maintained, 2020 NEC 300.4(A)(1) requires protective steel plate or bushing coverage, normally at least 1/16 inch thick. Measure from the hole’s edge, not its center.
Check the nearest edge
A centered hole can still be too large to leave the required setback. Check both sides where nails or screws could reach the cable.
Example: for a centered ¾-inch hole through the 3½-inch depth of a wood stud, the remaining wood on each side is (3½ − ¾) ÷ 2 = 1⅜ inches. That clears the electrical setback. A centered 1¼-inch hole leaves 1⅛ inches, so it needs the required protection.
These calculations check electrical protection only. They do not approve the hole under the building code.
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See CE courses and class datesHow thick must the plate be?
The usual minimum is 1/16 inch of steel, with enough length and width to cover the wiring area. The section also permits a thinner plate when it is listed and marked to provide equivalent or better protection. Do not assume any thin scrap metal qualifies.
The 2020 dwelling rough-in checklist is a useful companion for the setback and protection requirements.
Bored holes, notches and parallel runs
| Installation | Start here |
|---|---|
| Bored holes in wood | 300.4(A)(1): hole-edge setback and protection |
| Notches in wood | 300.4(A)(2): protect the wiring at the notch |
| Cable run beside framing or furring strips | 300.4(D): setback or required protection |
The details and exceptions depend on the wiring method. An NM-cable example does not establish the rule for every type of raceway.
Practice question
The edge of a hole carrying NM cable is 1 inch from the face of a stud. Is centering the cable inside that hole enough?
No. The hole itself fails the 1¼-inch setback. Provide the protection required by 300.4(A)(1). Moving the cable within the hole does not change the measurement.
Common questions
Does exactly 1¼ inches meet the setback?
Yes. The minimum is 1¼ inches. Check the actual dimension, not the intended drill location.
Does the NEC set the maximum hole size in a stud?
The NEC sets the electrical protection requirements. Structural drilling limits come from the building code and vary with the member and whether it carries load. For example, IRC R602.6 has separate stud-boring and reinforcement rules. Use the applicable building code and engineered-framing instructions.
Does a nail plate fix an oversized structural hole?
No. A cable-protection plate does not restore a damaged stud or joist’s structural capacity. For the electrical work beyond rough-in, see our box-fill guide and ceiling-box support rules.
Keep practicing
Try our most-missed NEC mock exam questions and 2020 NEC practice questions. For each missed answer, find the section in your code book, read the rule and work the question again.
Reviewed October 25, 2026, for the 2020 NEC. Use the edition required by your licensing exam. Follow the adopted code and local amendments on the job.
