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Stud Compromised?

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XR250

XR250

Structural
Jan 30, 2013
5,309
I am building a house. In one area, I have 2x6 studs @ 16" O.C., 5'-6" tall. The plumber needed to drill a 4 1/2" hole thru the dead center of 3 studs (the hole is centered top to bottom). I figured I would reinforce them with angle iron later. However, when I run the numbers on the stud as is (1/2" material left on each side of the hole), I end up with a combined gravity and wind load stress of under 700 psi for the remaining portion of the stud. They are #2 SPF studs. Should I even worry about reinforcing them?
 
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4-1/2" hole through a 5-1/2" member is serious stuff, even for a non-load bearing wall... Can you replace the studs with 2x8, either for the full wall to have it 'flat' or locally and have a bit of a bump out. If non bearing, the wall can likely do it. You might want to add metal strap to prevent nailing through the pipe. If the wall is bearing, can you add a lintel and then span across it.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik
 
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DIK,

It would be easier for me to reinforce the three studs with steel. The pipe is only 3 1/2"Ø so I can run a 1" angle iron down each side, The wall cannot be furred.
The hole seems big, but the numbers don't lie.
 
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If it's not bearing, you don't have much of an issue, the drywall will carry the load and lateral deflection would be the only issue. The angle isn't needed, other than it would stiffen the stud and make it difficult to put a drywall screw into the pipe.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik
 
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Dik,

It is an exterior wall so it is subject gravity and wind loads.
 
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I would add the angles if it were my house. 1/2" of wood on each side just doesn't look right.
Does the IRC have limitations of the max size of holes in a stud?
 
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I don't love it. You also need to transfer shear across the 1/2" remainder bits in addition to the flexural and axial stresses in those locations. Even if the holes are at mid-height, there's no such thing as a uniform wind load in real life. It's likely not an issue for such a short stud but I'd have to think that you've probably also lost half of your strong axis flexural stiffness in the studs as it would pertain to axial buckling.

I don't know how much is axial and how much is flexural stress here but, at 700 psi axial over the remainder bits, that's still 1000 lbs per stud. I certainly wouldn't want to be standing next to one of these studs with 1000 lbs coming down on them.

Can you make use of one of the Simpson reinforcement gadgets or are we outside of the range of applicability for those things?
 
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I agree it does not look right and I am sure it exceeds IRC requirements.
The question is more theoretical. If the demand is less than the capacity, why bother reinforcing them? The wall is sheathed in 7/16" OSB on the exterior FWIW.
 
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@Kootk,

Approx. 500 psi gravity and 200 is wind. Even if I put the total wind load on 1/2 the stud, the shear is only 28 lbs or 18 psi.
 
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5'-6" tall. Is this a basement/crawlspace? My concern is only for serviceability. There's redundancy in the sheathing (including gyp) and that house is only ever going to see a fraction of the design live load.
Also, if you do use angle iron, it will have to be decently long to develop the forces through a bunch of not very strong dowel fasteners.
 
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XR250 said:
Even if I put the total wind load on 1/2 the stud, the shear is only 28 lbs or 18 psi.
Click to expand...

To push that a little further, in this situation the shear would also add local flexural stresses to the remainder bits because you can expect the thing to act Vierendeel-ish across the hole.

In a fundamental, theoretical sense, I feel that the scale of things at the remainder bits is so small, and so dissimilar from Bernoulli principles design, that the basic M/Sx stuff doesn't really even apply. Across a hole that large, it's a joint, not the cross section of a conventional flexural member.

I'm not even convinced that the 1" angle is a good reinforcement choice but I guess that I'd need to see the details.
 
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When I imagine the vierendeel action, I kind of envision this happening.

Another thing to consider is that with typical wood setups, accidental eccentricities are ever present. It wouldn't surprise me in the least if 2/3 of your axial load ends up on one side of the stud.

C01_ki3h7l.png
 
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All good points, Kootk.
As far as the eceentricity goes, in this location the floor system cantilevers over the wall to form a balcony so that should keep the load fairly even.
I was planning on running 1x1x1/8" angle x 5 ft. on each side of the hole with a bunch of #9 Simpson SD screws.


Thanks for everyone's insight.
 
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You could maybe just frame it as an opening with a header, sill and jamb studs.
 
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XR250 said:
I was planning on running 5 ft. 1x1x1/8" angle x 5 ft. on each side of the hole with a bunch of #9 Simpson SD screws.
Click to expand...

Okay, that's pretty convincing.
 
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BONES206 said:
You could maybe just frame it as an opening with a header, sill and jamb studs.
Click to expand...
The vertical portions of the pipe prevent me from doing that. Nice thought, though
 
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Numbers aren't everything. The 1/2" each side of the hole might work on paper, but how reliable is the little 1/2" chunk of wood? It looks like you're going to reinforce anyway, just wanted to note that passing on paper doesn't always give you the real life pass. And of course, that goes the other way - failing on paper isn't always an immediate real-life fail. You know, engineering judgment and what not.
 
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XR, you can try a Simpson Stud Shoe SS1.5 that should work. They’re about $8/ea and will be easy vs drilling 1/8” steel.
Simpson_Strong-Tie_SS_16-Gauge_Galvanized_Stud_Shoe_for_2x_Lumber_SS1.5-R_-_The_Home_Depot_mxgbt3.png
 
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Would be nice but it maxes out at 2" pipe. I have 3" pipe.
 
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