We have a ceiling beam that is a standard 4x8 over 12 feet.

Let's stipulate that is properly sized for the weight load over that span.

But, what if, in order to place that beam, we need to notch it a bit on the very end: so it is a 4x6 for 2 inches where it rests on the post, but is then 4x8 the rest of the (unsupported) span.

I assume the deflection is now greater than when it was 4x8.

But is it degraded all the way to the deflection of a 4x6 ? Or is it somewhere inbetween ? This only happens on one end - on the other end, it is a full 4x8.

If it's somewhere inbetween is it ... just a bit weaker than a 4x8 or just a bit stronger than a 4x6 or ... ?

Thank you.


1 Answer 1


A notch in the end of a beam does not affect the strength (or deflection) of a beam, unless it’s more than 1/4 th the height of the beam (or joist) at the ends out to the face of the bearing point. (See Code ICC R502.8.1)

Code does not allow notches in middle 1/3 span and Code allows 1/6 th depth of beam in the last 1/3 rd span at each end of beam.

In fact, in your case, you could probably cut the whole end of the beam off where it’s notched and it would not affect it structurally. (That size beam needs about 2” of solid bearing, depending on the grade and species.)

  • Thank you. To clarify, you are saying that if we notched the very end of our 4x8 and our notch was less than 1.8" tall (1/4 of a 7.25" 8x) then the deflection is not degraded, yes ? I am not on-site to measure, but I think it's more like 2-2.5 inches, but you think it still doesn't change anything ? Thank you again.
    – user227963
    Commented Jan 17, 2020 at 1:21
  • @user227963 Yes, that’s correct...because you didn’t notch it out to the face of the bearing, it doesn’t matter, as long as you leave adequate bearing, which I’d guess to be about 2” minimum.
    – Lee Sam
    Commented Jan 17, 2020 at 2:58
  • Forgive me - what is the face of the bearing ?
    – user227963
    Commented Jan 17, 2020 at 6:03
  • @user227963 Clear span is face of bearing to face of bearing. (The distance BETWEEN bearing points.)
    – Lee Sam
    Commented Jan 17, 2020 at 6:52
  • Not sure if I can come back to this a week later, but I think there was a misunderstanding ... we did not take a notch out of the end of the beam (which would make the beam shaped like a "C") we took a notch out of the bottom of the very end (which makes the beam shaped like an upsidedown "L"). We rest the 4x8 on a wall, but the pitch of the roof caused the wall to hit about two inches higher than bottom of the 4x8, so we had to notch out the bottom two inches of the 4x8 so it would be the right height. You still think no problem ?
    – user227963
    Commented Jan 28, 2020 at 21:54

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