How much can you notch or bore a floor joist?
Notches cannot exceed one-sixth of the depth and holes cannot exceed one-third of the depth (IRC R502.8.1, 2012 edition).
Notches must not be longer than one-third of the depth and cannot be located in the middle one-third of the span. Holes shall not be closer than 2 inches to the top or bottom of the member or to any other hole.
Notches at the ends of a member shall not exceed one-fourth of its depth. The tension side of members 4 inches or greater in nominal thickness shall not be notched except at the ends.
This answer is based on Section R502.8.1 of the 2012 IRC. Section numbers and details can change in later editions and through state or local amendments, so confirm the edition your jurisdiction enforces with your building department before you build.
Related answers
- How much bearing do floor joists and girders need at the ends? — IRC §R502.6
- What is the anchor bolt spacing for a sill plate on a foundation? — IRC §R403.1.6
- How do I attach a deck ledger to the house? — IRC §R507.2
- How big does a crawl space access opening have to be? — IRC §R408.4
Need this scoped to your jurisdiction?
Adopted edition and local amendments vary by city and county. Ask Donnie checks your jurisdiction and cites the exact adopted section.
Ask Donnie →General information based on the International Residential Code (a model code). This is AI assistance to verify — not legal advice. Confirm the adopted edition and any local amendments with your local building department (AHJ) and a licensed professional before you build.