Notching and Drilling Code — Joists, Studs & Top Plates
Every trade drills the frame, and the IRC gives each member a budget: how deep a notch, how big a hole, and where. Blow the budget and the fix is a strap, a header, or an engineer.
Worth knowing
- Engineered lumber has no notch budget at all outside the manufacturer’s literature — never field-notch an I-joist flange (R502.8.2).
- The classic violation is the 3.5 in. hole saw for a DWV stack through a 2×4 bearing wall: a 3.5 in. hole in a 3.5 in. stud is 100%, not 40%.
- Kitchen and bath remodels concentrate all three rules in one wall — plan chases before demo, not after rough-in.
- Straps and shoes from framing hardware makers are code-friendly fixes, but they repair plates, not joists — an over-notched joist gets sistered or engineered.
Common questions
What does the code say about joist notches for Notching & Boring?
Notches no deeper than one-sixth the joist depth, no longer than one-third the depth, and never in the middle third of the span; end notches up to one-fourth the depth. (IRC R502.8.1)
What does the code say about joist holes for Notching & Boring?
Holes no larger than one-third the joist depth, kept at least 2 in. from the top and bottom edges and from any other hole or notch. (IRC R502.8.1)
What does the code say about bearing-wall studs for Notching & Boring?
Notches up to 25% of stud width; bored holes up to 40% — 60% only when the stud is doubled and no more than two successive studs are bored. (IRC R602.6)
Adopted edition by state
Base-code year from BuildSpec’s adoption records. States often amend the base code, and your city or county may differ, so confirm with your building department.