Deflected Cantelevered Beam

[Paul Dickerson]

I measured 1.25" of deflection at the end of this 4x10 cantelevered beam supporting the corner of the roof. The beam is cantelevered 68". How much deflection is too much in a cantelevered beam? Does L/360 work for cantelevers? That is only 3/16" in this case.

I am definitely going to write this up, but I was looking for a guide to use for situations that aren't so obviously bad.

[Barry Adair]

IRC Table R502.3.3(1) covers this partially read this for further info

http://www.bssconline.org/Homebuilde...pter4final.pdf

[Kenton H. Shepard, CMI]

Originally Posted by pdickerson

I measured 1.25" of deflection at the end of this 4x10 cantelevered beam supporting the corner of the roof. The beam is cantelevered 68". How much deflection is too much in a cantelevered beam? Does L/360 work for cantelevers? That is only 3/16" in this case.

I am definitely going to write this up, but I was looking for a guide to use for situations that aren't so obviously bad.

How do you know it's deflection, Paul? It might have been bowed when it was installed, it might have bowed as it dried or the top plate might not be level and so the beam it supports won't be level.
Then again it might only sit on the wall for 2'.
Sounds like you're doing an engineering calculation.

[Paul Dickerson]

It was deflection without a doubt, and it was all concentrated at the point of the cantelever where you would expect. When I sighted down the plane of the roof, it stuck out like a sore thumb.

Is measuring deflection and comparing what you measure to what is printed in code books engineering? If so, than I am guilty as charged.

I have a good understanding of building codes and some understanding of the principals of structural engineering. I never quote it, but I use it every day to help guide my recommendations.

But back to the question at hand. I have seen several examples of deflection of cantelevered beams, and I would like to have a less subjective method of determining when a structural review should be call for.

[Kenton H. Shepard, CMI]

Originally Posted by pdickerson

...I would like to have a less subjective method of determining when a structural review should be call for.

You have a lot of company there!
I wind up calling similar conditions out as being "consistent with long-term failure due to inadequate structural design. The Inspector recommends evaluation and correction..." either a qualified contractor or structural engineer depending on the situation.

Was there a similar overhang at the opposite corner which was also out of level?