Notched Floor Joists

2x12 floor joists are notched to 5" to set into main beam and then sistered. Is the max allowable notching 1/4 of the joist? Home was built in 1980. No issues.




R502.8.1 Sawn lumber. Notches in solid lumber joists, rafters
and beams shall not exceed one-sixth of the depth of the member,
shall not be longer than one-third of the depth of the member
and shall not be located in the middle one-third of the span.
Notches at the ends of the member shall not exceed one-fourth
the depth of the member. The tension side of members 4 inches
(102 mm) or greater in nominal thickness shall not be notched
except at the ends of the members. The diameter of holes bored
or cut into members shall not exceed one-third the depth of the
member. Holes shall not be closer than 2 inches (51 mm) to the
top or bottom of the member, or to any other hole located in the
member. Where the member is also notched, the hole shall not
be closer than 2 inches (51 mm) to the notch.

(That said, I can’t tell what’s going on in your photos.)

5" are cut, 6" remain. I was looking for the reference. Thanks Joe.


Now I see.



Any notch at the end of a 2x lumber beam or floor joist is problematic. A square cut notch has the tendency to split along the grain of the wood. Its better to avoid a square corner by rounding the cut. Ideally they should have used metal hangers. Also it appears to me the location of the board they added would not prevent the original board from splitting.

If they sistered a 2x12 instead of a 2x6 that may have been a little better but still it’s not good. House was 31 years old and no issues but this was a bad modification for sure. Back then, this was unincorporated and probably wasn’t inspected by the AHJ.


I hear the same thing when it comes to structural issues, “Its been that way for 20 years.”

My response is typically all engineered designs and prescriptive requirements outlined in the building codes have a safety factor built in to account for unforeseen loads, variations in material properties, variations in the skill level of the person(s) constructing the object you designed. All these variations and mistakes can accumulate until the safety factor is diminished to one. This means the buyer, i.e. your customer, has no room for error. Just one more attempt to do a DIY job, move a wall, add a hot tub or cut a notch in a floor joist just might bring down the deck, crack the drywall, etc. Funny thing about structural failures is some take a long time to occur like foundation settlement, but some happen in an instant like a deck collapse. So just because nothing visible has happened in 20 years doesn’t mean it won’t happen tomorrow. If a structural failure occurs you can bet the lawyers what to know three things:

  • Who designed it?
  • Who built it?
  • Who inspected it?

Ever wonder why windows of Boeing 767, 747 ect are rounded on the corners?
Same Idea is to prevent stress on the corners that don’t exist.:smiley:
Same principle should be applied as Randy has pointed out once again teaching the engineering side.
Love to hear you Randy, you are always there to help out on this MB daily.

This inspection was for a real estate lawyer that regularly sends me all of her clients that get past the Realtor that advises “you don’t need an inspection”.
I think the builder designed it, built it and inspected it. It was the floor of a “sunken Living Room”.
I told the buyer it may last another 30 years with no problems but it ain’t right.

Typo in this graphic - row 2 states 1/16 rather than the correct 1/6

Chad report that to Ben or Nick and they will correct that typo. Good catch!!


Graphics Department updating, and a package of goodies is coming to you Chad. Thanks.

OK Chad we will settle up later.\:D/\:D/\:D/\:D/

Fix made:

Replaced in


Attached are pics from a centenial home on the topic; it eventually fails.