Ledger to Wall Stud Connection

[csways]

Hi,

I've been tasked with designing a ledger to wall stud connection for an exterior stair landing. The landing spans from the ledger to a post-supported beam. I can get the numbers to work with 1/4" lag screws, but I am hesitant to proceed as the only literature I have on a similar connection is from Simpson and I am unable to meet their spacing and end distance limitations.

Does anyone have any guidance or suggestions?

Thanks!

 

[dhengr]

Csways:
You say…, “I thought there was a code reference prohibiting attaching a ledger to something toe-nailed, but I may be incorrect.” I’m not sure of a code prohibition, but ledgers should be secured to some substantial structure which can not just be peeled off the side of the building, with minor lateral loading. So, common sense and some engineering judgement and experience would lead you to that same conclusion. The toenailing isn’t worth a damn when it is done right, which is seldom the case. The blocking btwn. studs and bearing on the sill pl. should certainly be adequate for the gravity loads. But, this landing should probably have some lateral loading resistance, not unlike the same discussion for decks. In an emergency people come rushing out onto that landing and turn the corner to go down the stairs, creating a substantial lateral loading. The/a better solution would be some blocking btwn. the fl. jsts., two or three jst. spaces back into the bldg., end nailed through the jsts. and well nailed through the fl. sheathing (glued and screwed). Maybe some lt. ga. stl. angles from blocking to the fl. jsts. Then, threaded rods from a couple landing jsts. to the blocking back in the bldg., with appropriate end connection hardware. This would get any landing lateral loads back into the bldg. fl. diaphragm.

 

[KootK]

I’m not sure of a code prohibition, but ledgers should be secured to some substantial structure which can not just be peeled off the side of the building, with minor lateral loading.

Quite similar to ron's post idea, I would:

1) Use the blocking for gravity load as needed and;

2) Lag the ledger into the studs for lateral.

 

[csways]

@dhengr and @KootK

Are you stating that the ledger can be attached to horizontal blocking between the wall studs?

I will provide a supplemental lateral connection per IRC R507.9.2.

 

[KootK]

Are you stating that the ledger can be attached to horizontal blocking between the wall studs?

I certainly am. There is a small eccentricity to be resolved of course.

 

[BridgeSmith]

If it was me, on my house, I would look very hard at dispensing with the ledger altogether and extending the landing joists to the first floor joist. I'd align them so they are against the studs and support them on the bottom plate (shimmed as required). I'd screw the landing joists to the studs and install lags or timber construction screws through the floor joists, or use angles or joist hangers on the facing side. A few cleats/furring strips on the landing joists to attach the sheathing, and some sheathing, carefully notched around the landing joists, and it's ready for siding.

But that's just me. I have no idea whether that would pass muster with your local code.

 

[dhengr]

Csways:
Nails are certainly not the preferred fasteners btwn. the ledger and the bldg. structure, either the top pls. or the blocking, to take the gravity loads. Where is the wall sheathing in your latest sketch? I would lower the ledger several inches so you stepped down a couple inches onto the landing deck from the interior fl. elev. The ledger can be lag screwed or structural screwed into the blocking and the top pls. for the gravity load. But, the blocking can be fairly easily pulled out of the bldg., so I would not use them for the lateral restraint. There should be flashing behind the ledger tied in with the flashing around the door opening, including end dams, at the ends of the ledger. And then, there should also be flashing under the door threshold and behind the sheathing or its moisture plane material, and out over the top of the ledger, and the joints btwn. the ledger and the landing joists. You might want some type of peel-n-stick tape on top of the landing joists, and under the decking.

HotRod10 – Generally, exterior beams and joists penetrating the sheathing and extending to the interior are very problematic, particularly in terms of flashing them well, to keep all moisture out of the wall. These could be beams cantilevering from the interior or exterior beams/jsts. bearing on the exterior wall top pls. And then, you have that problem detail a bunch of times with the landing joists.

 

[BridgeSmith]

I can see where restoring the building envelope around the joists could be tricky. If it was a 10' or 20' wide deck attaching to the wall, I'd probably look for another solution. I understood this to be a landing at the top of stairs, so I assumed there would be probably only 4 joists that would require special attention for flashing, etc. to seal around them. Again, my preference would be to do the best structural solution and then detail it to make it work functionally for keeping moisture out and such.

 

[jayrod12]

Again, my preference would be to do the best structural solution and then detail it to make it work functionally for keeping moisture out and such.

This unfortunately is the largest difference in mindset between building engineers and bridge engineers. (No offence intended).

My firm does significant amounts of Building envelope restoration on top of our already full structural design dance card. All of our building envelope projects tend to have significant (and I mean some of the worst shit I've ever seen significant) deterioration of structure due to shitty building envelope performance. With buildings, envelope integrity is almost the most important factor to durability in the field. Being able to work the structure around the envelope is what separates the good structural guys from the phenomenal ones.

 

[BridgeSmith]

I know it's different world, jayrod. Professionally, I work as a bridge designer, but I also have done a significant amount of residential remodeling and repairs in my personal life. I agree that there's certainly greater opportunity to do something crappy when having structure protrude through the building envelope, but it's by no means guaranteed that it has to be. There's also no guarantee that if the envelope isn't penetrated that it'll be ok. Crappy attention to detail will pretty much always result in poor performance, and I've seen the results of that over and over.

I'm not suggesting that what I proposed would be something to set a typical contractor loose on; only that it could be done successfully with the proper attention to the details.

 

[jayrod12]

Agreed. .

And don't get me wrong, I indicated in my first post almost essentially what you said you'd prefer to do. However at that time I was under the impression it was interior for some reason.

 

[gte447f]

@dhengr and @KootK

Are you stating that the ledger can be attached to horizontal blocking between the wall studs?

I will provide a supplemental lateral connection per IRC R507.9.2.

Exactly this. This is similar to a deck ledger attachment to a rim joist, except that instead of a rim joist you have a conglomeration of blocking/studs/bottom plate/top plate. Fasten the ledger to the "rim joist" (aka blocking, etc. in your case) with lag screws or through bolts for vertical load, and also provide 2 threaded rod connections for lateral loads. See AWC DCA6 deck guide for these connection details.

The one thing I don't like is the fact that, since you do not actually have a solid rim joist member, your lag screws may penetrate right at the interface between 2 pieces of wood, like, for example, at the vertical interface between a stud and a piece of blocking. The shear capacity of the screw in this case will probably be less than the code values. I do not know what to do about this?

 

[csways]

Update...

There is no appetite for a lateral connection using the two threaded rods, but I think I can get this detail, based on the Simpson Strong-Tie's 750lb assembly, approved.

Does anyone see any issues?

Ledger-to-blocking fasteners are not shown for clarity.

 

[gte447f]

What's the point of the blocking attached to the deck joists? Why not attach the DTT1Z directly to the deck joists?
Also, I would make sure that exterior wall is braced on the interior by blocking installed perpendicular between the interior floor joist and the wall top plates.

 

[csways]

I don't have a good answer; that is how the detail is drawn.

 

[Celt83]

looks like the blocking is to get the timber hex installation into the wall top plates assuming they don't align with bottom of the landing joists.

Open Source Structural Applications:

https://github.com/buddyd16/Structural-Engineering

 

[KootK]

With regard to the lateral connection, I was just envisioning some 1/4" SDS screws through the exterior ledger and into the wall studs.