Ledger - Stud Wall Connection w/ Lags: Shear or Bearing?
Ledger - Stud Wall Connection w/ Lags: Shear or Bearing?
(OP)
Hi Everybody,
I am designing a deck w/ a 4000 lbf jacuzzi & 210 psf snow load. I end up having that each joist (@16" o.c.) bears on the 4x ledger (w/ hanger) with a total load of 1500 lbf. I want to use lags to connect the ledger to the 2x6 studs in the wall. Using the NDS ASD Table 11J (& applicable factors), I get that I need 3- 3/4" lags @ 16" o.c. That just seems ridiculous... Also, I am concerned that the large lags will cause the wood to split.
Can it be argued that it is bearing (Table 11.3.2), rather than shear that controls? Or do I need to specify a closer lag spacing w/ blocking between studs?
Thanks,
cmhski
I am designing a deck w/ a 4000 lbf jacuzzi & 210 psf snow load. I end up having that each joist (@16" o.c.) bears on the 4x ledger (w/ hanger) with a total load of 1500 lbf. I want to use lags to connect the ledger to the 2x6 studs in the wall. Using the NDS ASD Table 11J (& applicable factors), I get that I need 3- 3/4" lags @ 16" o.c. That just seems ridiculous... Also, I am concerned that the large lags will cause the wood to split.
Can it be argued that it is bearing (Table 11.3.2), rather than shear that controls? Or do I need to specify a closer lag spacing w/ blocking between studs?
Thanks,
cmhski






RE: Ledger - Stud Wall Connection w/ Lags: Shear or Bearing?
Is the 210 psf a typo? That would be about 20 to 30 feet of snow! Are you connecting your joists to the face of an existing wall? What is the cladding? Better connection would be to place studs under joists or provide beam and columns adjacent to wall similar to what you must have on the outer side. When you say 4x ledger, what do you mean? In summary, not enough information.
RE: Ledger - Stud Wall Connection w/ Lags: Shear or Bearing?
It is a lot better than lag bolt. I will look at my simpson catalog when I am at work.
RE: Ledger - Stud Wall Connection w/ Lags: Shear or Bearing?
RE: Ledger - Stud Wall Connection w/ Lags: Shear or Bearing?
RE: Ledger - Stud Wall Connection w/ Lags: Shear or Bearing?
RE: Ledger - Stud Wall Connection w/ Lags: Shear or Bearing?
RE: Ledger - Stud Wall Connection w/ Lags: Shear or Bearing?
If you provide the extra girder for the verticzal loads all your connection to the wall studs will have to resist is the lateral loads for wind and seismic.
RE: Ledger - Stud Wall Connection w/ Lags: Shear or Bearing?
Well, I guess you can always add girder right next to the wall or frame the joist the other way and rest the girder in the wall.
RE: Ledger - Stud Wall Connection w/ Lags: Shear or Bearing?
It has several articles co-authored by Frank Woeste, P.E. regarding testing that has been done on deck ledger connections and guardrail connections.
I think a review of those articles would discourage you from using lags or through bolts to attach your ledger to the wall studs.
RE: Ledger - Stud Wall Connection w/ Lags: Shear or Bearing?
RE: Ledger - Stud Wall Connection w/ Lags: Shear or Bearing?
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RE: Ledger - Stud Wall Connection w/ Lags: Shear or Bearing?
RE: Ledger - Stud Wall Connection w/ Lags: Shear or Bearing?
RE: Ledger - Stud Wall Connection w/ Lags: Shear or Bearing?
Thanks for the all the replies! And yes, we have "Sierra Concrete" here in Mammoth Lakes, CA. Actually, the 210 psf is if I assume that the snow is showeled when there is only 6 ft of it covering the deck. Last year we got 668 inches of snow over the season! And most homes are owned by 2nd homeowners, i.e., they are not necessarily around to showel their decks.
In general, the owners don't like to have a "forest" of posts underneath their decks as it obstructs the view from the downstairs windows. That is why I'm trying to avoid specifying girder/posts close to the wall.
The weird thing is, that the typical existing decks here have survived just fine with face mount joist hangers nailed onto 2x ledgers, which in turn are connected to the studs with 1- 5/8" lag @ 16" o.c. Generally, the failures occur when the soil builds up around the bottom of the outside posts (over decades of poor landscaping management), leading to dry rot.
To COEngineer: the 4x ledger gives a higher capacity per lag than a regular 2x according to NDS ASD Table 11J.
Thanks,
cmhski
RE: Ledger - Stud Wall Connection w/ Lags: Shear or Bearing?
RE: Ledger - Stud Wall Connection w/ Lags: Shear or Bearing?
Yes, the joist hangers are connected to the ledger. That part is easy... The tricky part is connecting the ledger to the rest of the house... In order to get the highest possible capacity according to NDS ASD Table 11J, the main members have to be loaded parallel to grain, i.e., the lags have to be going into the studs, rather than the rim board.
cmhski
RE: Ledger - Stud Wall Connection w/ Lags: Shear or Bearing?
I like the answer some of the instructors in some log home building classes give to students who think they have a better way of doing things that have not been well thought out "You could do it that way, but I don't recommend it". You have choices and as an engineer it is your responsibilty to make the hard decisions. Putting that many lag screws into studs may work fine but I don't personally recommend it. I'm sure I do a lot of things other engineers would question that I feel comfortable with.
When a deck does fail it can have disasterous consequences and failing decks are becoming more and more prominant as builders and engineers stretch the materials and designs to the limit. Some people want to live in a glass house with nothing obstructing their view of the outside. If they want no obstruction go outside. oooouch!
Good Luck.
RE: Ledger - Stud Wall Connection w/ Lags: Shear or Bearing?
The ICC evaluation report with design values for LedgerLok screws:
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