Proper notching of floor joist

If a fellow NACHI member could further guide me…I know what the books say about notching a floor joist. What are the concerns for notching a 2 x 10 floor joist to accommodate a 3 in drain pipe to pass through. My thoughts are; that almost 1/3 of the board would be missing since the board is not exactly 10 in wide.

Some input would be helpful



This may be helpful.


Mike, where did you find that picture?

I don’t remember for sure but there was a very recent discussion here on this issue.

I’d install some additional additional support in the form of one or more metal bars, boards, or the like extending at least 2 feet (or to the end) on each side of the notch, and attach it at no less than 6 points (3 each side of the notch), David.

I don’t know the specific codes for such reinforcements, but since you’re making about a 3.5-4" notch it stands to reason that a well-attached 2x6 or metal bar of equivalent strength should be more than sufficient. When in doubt, overbuild.

And thanks for the schematic, Michael.