• Welcome to the new and improved Building Code Forum. We appreciate you being here and hope that you are getting the information that you need concerning all codes of the building trades. This is a free forum to the public due to the generosity of the Sawhorses, Corporate Supporters and Supporters who have upgraded their accounts. If you would like to have improved access to the forum please upgrade to Sawhorse by first logging in then clicking here: Upgrades

Cantilevered Beam

darcar

darcar

Silver Member
Joined
Nov 12, 2009
Messages
129
Take a look at this picture and tell me if you see an issue OR what what point cutting the end of a cantilevered beam becomes an issue.In this particular case a ouble 2x12 beam was angle cut at the end for appearance, but only 4" was left before the angle took off.Additionally the spacing of the joists are at 24" OC instead of the more common 16"OC.This particular builder takes the minimum code and pushes that as much as he tyhinks he can get away with it.Outside of consulting an Enginerd, I don't feel comfortable making the determination on each deck. I'm not the designer.Thanks for your input.Fire away!

View attachment 1743

View attachment 1743

/monthly_2012_12/deck.JPG.19d9596f51a7edb98d4901d92e4fac38.JPG
 
Looks fine to me. In a cantilever it is the top of the beam/joist that is most critical, which is in tension; and the depth is important where the moment force is greatest, which is back at the point where the cantilever begins.

Picture a shelf bracket that is larger at the point where it connects to the wall and tapers down towards the edge of a shelf.
 
brudgers, you're correct, the condition is overhanging. However, the principles are nearly identical, except that the overhanging portion benefits from the loading on rest of the beam, and vice versa, thus minimizing the moment force. This allows a smaller depth in the beam/joist.
 
Dar raises a good question though. At what point does the beam no longer work as designed. Obviously can't start the angle cut at 0", what about 1" down, 2" down, etc?
 
mjesse said:
Dar raises a good question though. At what point does the beam no longer work as designed. Obviously can't start the angle cut at 0", what about 1" down, 2" down, etc?
Click to expand...
Seems to me that you could start the angle cut at whatever depth would work for a beam without the angle cut. So, if 4" of depth were required to carry this overhanging load, then the angle should not start before 4". I've had concern with this condition in the past, and unfortunately, it has resulted in a judgement call each time. Is the inspector "comfortable" with the condition? Not a great yard stick, but the only one we have without perscriptive language from the code, or PE involvement.
 
The load on that joist is about one half the distance to the next joist mutiplied by half the joist length times thetotal load. In-other-words, not much of a load on that end of the beam. I'd be more concerned with the post seemingly screwed into the face of the band.
 
I'm kind of concerned about how the spread beam is connected to the post.
 
I'm guessing the girder is hanging just on bolts at the post, figure 9 in DCA6 vs the approved figs 4&8
 
DRP said:
I'm kind of concerned about how the spread beam is connected to the post.
Click to expand...
Yeah, the first thing I see are two single member beams that appear to be screwed to the side of the support post from both sides. Big problem. Not worried about the angle cut in the least.

Deck construction is a mess of confusion in this country.
 
brudgers said:
It's not cantilevered. It's overhanging.
Click to expand...
But isn't it the case that in construction we use the term cantilever for this situation?

The below is from the 2010 CRC:

2.2. Floors shall not cantilever past the exterior

walls.

If I'm not mistaken they are referring to a floor overhanging the exterior wall. There's many more examples in the building codes where an overhanging situation is referred to as a cantilever or am I missing something?
 
Ok with the deco cantilever end design, but I feel about the same as Glenn and Bill Cower in regards to the single beam attachment, Cower does not look happy!

Fear that's two single beams attached to the outside of the post, probably not notched?

pc1
 
Here's another example from the 2010 CRC:

4. For wood-frame construction, a continuous

rim joist is connected to ends

of all cantilever joists. When spliced,

the rim joists shall be ..............
 
Rio said:
But isn't it the case that in construction we use the term cantilever for this situation? The below is from the 2010 CRC: 2.2. Floors shall not cantilever past the exterior walls. If I'm not mistaken they are referring to a floor overhanging the exterior wall. There's many more examples in the building codes where an overhanging situation is referred to as a cantilever or am I missing something?
Click to expand...
"Cantilever" when applied to beams has a specific technical meaning including bearing conditions and equations to determine code compliance.
 
addressing the seemingly insuficient fastening method of the beam to post...

The fasteners used are ledger locks (generic term - each manufacturer has its own brand name). We see these more and more often in place of lag bolts. There are two on each beam into the post.

And as far as the screws into the end grain of the joists, that has been common place ever since I was building decks 20+ years ago. Do you require hangers there also?
 
Hanging on ledgerlocks, lags, bolts... where are you seeing the minimum bearing being met in that? Which member of that beam is taking almost the entire load?

The rail needs to be able to take 200 lbs in any direction, the infill pickets #50/sf.

DCA6 is worth looking at.
 
Ledgerloks have their place but they're being missused. Contractors can't tell me the length, spacing nor the quanity it takes to fasten a deck ledger, I find myself doing a lot of new product reading lately. Don't even mention CSST!

pc1
 
Last edited by a moderator:
I take it back... there are three of the ledger locks thru each beam into post.

I have a call into our local Simpson Strong Tie supplier to see how he suggets we approach ledger locks in beam to post application. How many per etc. similar to their requirements for leaqdger lock spacing at the ledger.
 
In a side bolted beam the weak member in the connection is the wood, not the bolt. That is likely the case with the structural screws as well, depending on span of the beams. You won't find any information on that connection from the structural screw manufacturers.
 
You must log in or register to reply here.
Top