Tall Wood Stud Wall Framing without Full Height Studs.....HOW?? 2

[BA_zach]

Hypothetical wall section attached.....

Has as anyone ever dealt with a tall single story wood framed building, where the wall height is tall enough where full height studs are not feasible. This results in a bottom portion of the wall and a top portion of wall, which creates a "hinge" in the wall. I am curious if anyone has ever encountered this and how this is dealt with. There has to be wood framed buildings out there with this type of scenario.

I am looking for y'alls thoughts, discuss, experience. Where I am perplexed is wind load on the face of the wall, obviously resulting in shear and moment which needs to transfer across this "hinge". The shear transfer probably isn't a concern, transferring moment across this gets interesting. Do you put metal strapping each side of the studs designed for the decoupling forces? Do you consider composite action with the exterior sheathing and then require interior sheathing also for composite action?

Yes, kickers up to the roof structure would be the easiest, but this isn't an option. I look forward to everyone discussion.

 

[XR250]

What are the circumstances that require this?

 

[DaveAtkins]

I have used double studs for this situation, with the joint between the upper and lower stud staggered. The stud is designed as a single stud, since where the joint occurs in one of the studs, the other stud is continuous.

DaveAtkins

 

[RWW0002]

Why are full height studs not feasible? Moment connections in wood are generally not a great idea (maybe not impossible, but definitely not ideal).

If this is a design job, I would try to find a way to make full height studs feasible. If this is a field condition, I would be looking for some way to brace the hinge. Staggered splice connections or strapping on the face would be a last ditch effort and would require significant rigor to design..

 

[BA_zach]

@XR250: I am going through design of a wood building and it was something I started thinking about. But I've somewhat come to the conclusion, if you have a single wall stud span of 20 ft or less a single member should still be able to be accommodated. If the wall stud span is greater than 20ft, use engineered lumber and the longer span should be able to be accommodated. Shall you need a longer span than engineered wood, don't use wood anymore and use steel.

This was just something I started thinking about when I was going through the design and it perplexed me and was curious if anyone has ever encountered this scenario.

 

[Celt83]

If the Height is greater than stock nominal lumber then use LSL studs

Also make sure you are not violating the slenderness ratios:
For a location falling under NDS a 2x4 wall would be limited to 14.58' and a 2x6 wall would be limited to 22.92' to meet Le/d<=50.

My Personal Open Source Structural Applications:

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

Open Source Structural GitHub Group:

https://github.com/open-struct-engineer

 

[Canuck65]

Agree that taller walls typically use engineered lumber, like LSL studs. I don't see too many tall walls that require steel, although on occasion it does happen. I tend to avoid steel like the plague in these walls due to thermal issues in cold climates.

On occasion, usually due to the layout of windows not lining up, I have had to incorporate horizontal beams. For example, a horizontal beam could be used where you have shown a hinge in your original post. Need to make sure the ends of the horizontal beam tie into structure that can resist the loads. Often this approach leads to a bigger wall thickness.

 

[TheDW]

We'd use a wind beam

 

[jayrod12]

I've seen this done in practice, but the reason I saw it is because the wall was as flexible as a trampoline and we were brought in to fix it. We ended up providing steel columns that were full height at a regular spacing, and then connected the wall plates at the joint to our steel columns. This fixed the bounciness.

In tall residential walls, to get standard lumber to work often your spacing needs to come down to 12" or tighter, which really isn't cost effective when you could likely get LSL or LVL studs to work at 16". It's more than just material cost to consider. Heavily framed walls have minimal space for insulation, and what space there is requires every piece of insulation to be cut to fit.

Often on walls that exceed about 14 or 15 feet I'll try to push for 2x8 studs so they can stay nicely at 16" o/c, then if they get closer to 18-19ft I recommend engineered lumber.

 

[DaveAtkins]

jayrod12,

I don't think the problem is structural, but rather the limiting length of stud available at lumber yards.

That is why I have used double studs with the joint staggered.

DaveAtkins

 

[Ron247]

I have run into this multiple times where the completed house has a real flimsy wall. They built two 10' walls with 2x4s for example and stacked them on top with the logic being the studs were only 10' long and therefore 2x4s are ok. The hinge is flimsy and the wall moves noticeably. The ones that move less have brick veneer. So the brick veneer is bracing the studs rather than the studs bracing the brick veneer. The city inspectors have passed this multiple times but I think now they have caught on.

You may be able to get 20' lumber but 2x4s don't tend to work at that length. They do not want to use 2x6s or 2x8s where I live.

The suggestions of lapping the studs and using engineered lumber are both solutions I have used. I have also used a whaler at one location to repair the wall as someone else suggested.

The worst I have run into are 20'+ tall Great Rooms with nothing but windows looking out over the lake. The entire 24' wide room is supported by two walls of 2x4 studs stacked on top of each other but there are only 8 studs in the each wall since most of the wall is glass. I have had my wife push on the huge walls with a broom handle at the top the doors and you can see the wall move 3". These also, passed inspection. Thank God, wind can't run across the flat lake, then hit the 50' tall sloped embankment up to the Great Room wall.

 

[jayrod12]

The problem is most definitely structural. At walls that tall, 2x6 studs are really pushing the limit for deflection. And often, tall walls are filled with windows, or at a minimum have a couple of windows in them. That just exacerbates the issues. On a load bearing tall wall, even just minimum eccentricity, or combined wind and gravity loads would likely fail the studs. And if it doesn't, it would be so damn close to capacity it would be worrisome.

On a relatively new build, if I opened up the walls and saw studs that were spliced the way some of you have indicated, I'd be recommending they get removed and reframed. The only time I let that sort of thing fly is on repair work when it's only one or two studs in an entire wall that need to be spliced. I would not even start the conversation on a new build.

A couple other points for consideration, on a previous tall wall thread and even perhaps above in this thread, I made a comment about pre-cut insulation and how they come in 14.5" wide and 22.5" wide batts. They do not come in 10.5" wide, nor 13" so doubling up studs or going to 12" o/c requires cutting of every piece of insulation and therefore additional labour. Have you ever come across reasonably straight 16-20ft tall 2x6? I haven't. They might be within tolerances from the mill, but once they've been soaked by rain, sat in the yard, dried out on one face, they're warped like crazy. Your drywall ends up looking like shit. People want these fancy features in their house, they have to understand that comes with a price.

And really, you've got a single wall, or two walls of an entire house done in LSL studs, so let's say instead of that wall costing 10 bucks a stud it costs 15, so what? 40ft of wall that equates to 30 studs, are we going to argue over $150 on the overall costs of the structure? You're picking the wrong battle. You could save that $150 by changing the faucets and toilet to the one model cheaper.

 

[KootK]

1) I've never done this before. Just interested in the discussion.

2) I'm sure that the points about insulation and economics are good ones. For now, I'm just interested in structural performance.

3) My comfort level with the spliced studs would be dependent on how the splicing was done. I like the one on the left more, and the one on the right less. Which reflects how this is is typically done?

 

[DaveAtkins]

The "MORE GOOD" option is what I have been promoting in this thread. As I said earlier, the double stud must be designed as a single stud, because at the splice, only one stud passes through. If a double 2X6 does not work, you must use a double 2X8, or a double 2X10, or a triple 2X6, or whatever works. But the concept is sound.

I interpreted the original post to be about constructability, not whether a 2X6 works at that height.

DaveAtkins

 

[Ron247]

I was talking about More Good option except I did not have the blocking present. The exterior face was OSB. Due to the height, I could keep the cuts about 5' from the top on one, and 5' from the bottom on the other. The contractor wanted to do the Less Good, but I felt the potential twist could add to nail pops in some fashion in addition to the unsymmetrical issue. Mine was too tall for a single 2x4 to work, so it was 2x6s spliced like this. We had to cut the spacing down to 12" because studs at 16" would not check out.

 

[masonrygeek]

With the high cost of lumber and the difficulty in this detail, just change it to a masonry wall. A little thicker, but you can sleep at night.

 

[Ron]

Agree with DaveAtkins' approach. Have used this method.

 

[BridgeSmith]

While the "more good" option could conservatively be designed as a single stud, at midspan, where the moment is highest, it would have the capacity for bending of both studs.

Rod Smith, P.E., The artist formerly known as HotRod10

 

[Celt83]

I'd really call those details not great and not at all.

By the time you've worked out all the fastener detailing to make you think that thing will behave like you hope it will you would have chewed up enough billable time to cover the material cost to just switch to the full height LSL studs. If we are talking about home construction good luck having the framer actual follow your fastener detailing and not just going to town with their nail gun.

While the "more good" option could conservatively be designed as a single stud, at midspan, where the moment is highest, it would have the capacity for bending of both studs.

Only if you specify that the joints do not occur at/near the mid-span/mid-height of the wall and it's actually built that way.

My Personal Open Source Structural Applications:

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

Open Source Structural GitHub Group:

https://github.com/open-struct-engineer

 

[BridgeSmith]

Only if you specify that the joints do not occur at/near the mid-span/mid-height of the wall and it's actually built that way.

Yes, it would have to be built as KootK detailed it.

Rod Smith, P.E., The artist formerly known as HotRod10