Number of King studs for an 11′ opening?
Tiziano
| Posted in Building Code Questions on
IRC Table R603.7(1) requires 2 King and Jack studs for each end of openings that are between 10′-6″ and 12′ when framing 24″ OC. But, it requires 3 each for 16″ OC.
What gives?
And, is the planned framing in the attached image ok using 2x6s?
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The idea, which if I recall correctly from older versions of the code, is that the total number of studs needs to match what would be there if there wasn't an opening. It's about lateral loads, perpendicular and parallel to the wall, not vertical loads.
Interesting. The logic makes sense, sort of. And yet, if it was a clear span there would be 7 missing studs.
As for my framing, since the header is not really a clear span of 11' (I'm also supporting at a 1/3 and again at 2/3 of the way across), I'm probably fine (?).
Here's a diagram that shows an 11' header with 24" o.c. stud spacing. You are replacing six studs with four king studs and two full-height jack studs. I run all jacks full-height but most builders seem to like to split them with the sills.
Your framing layout looks ok but it looks like your layout is 12" o.c., not 24". If you have a built-up header you don't need the extra plate below it. You don't need jack studs under the window sills; it's common practice, but except for very heavy windows, the sills typically support very little weight. A single nail can support about 150-200 lbs so three nails in each sill would easily handle the weight of the windows. Having the interior jack studs full-length is important so you avoid a hinge point. Every stud is a place you won't have insulation, so not overdoing the framing will help with energy costs, comfort and carbon emissions.
As Michael said it’s more about forces perpendicular to wall. You need king stud build up because it goes from plate to plate. Intermittently supporting header does not help in this regard. Though yours looks like your header is tight to top plate so if you are worried about stiffness (have a glass swing door or long distance between braced walls) it might help to fasten header to top plates.
As an example, I recently built a structure with a 3.5’x8’ triple pane glass swing door (very heavy) and had to beef up the king studs substantially on either side and on adjacent windows in order to reduce wall movement when the door closes (plus we had to add some shear transfer clips at plates). This was a tall gable end wall, but just an example of importance of king stud.
Thanks guys.
2x6, 16" OC. My build helpers are both contractors and do not like 24" OC. But that's another issue I'm working on. :)
Not clear in my image was that the built-up header has 2, 1.75" deep LVLs to the inside and 2" exterior rigid insulation. The plate below the header is used as a nailing area for the window flanges due to the rigid on the outside of the header. In fact, the split jack studs on both sides of the stacked windows are used as flange nailing areas as well.
No doors on that wall, just an array of fixed picture windows.
With 16" o.c. spacing you're supposed to have three king studs and three jack studs at each end of the header. I guess you could count the center jacks but you only have two kings at each end. It's not something that code enforcement often worries about, in my experience, and there is so much wood in your wall I'm sure you'll be fine.
I know the typical approach is to go with the on center spacing no matter what, but in some cases, like yours, it can make sense to adjust the layout.
Many contractors don't like 24" o.c. studs or joists, though most are fine with 24" o.c. rafters. In most cases it doesn't save enough wood or energy to worry about, in my opinion, especially if you have to go with 5/8" drywall as a result.
"Many contractors don't like 24" o.c. studs or joists, though most are fine with 24" o.c. rafters." Yep. That's what my guys are ok with.
Single story, mono-slope roof. The wall in question is the high wall.
Tiziano,
Is it an 11'-0" opening? The header is that length (although it could be broken up, and that's the way I would have framed it), but if there are intermediate jack studs on each side of the windows, isn't it really three smaller ones?
11'-0" opening, yes and no. Functionally no, now that I think about it. It's an 11'-0" header, but the openings beneath are divided 3', 4', and 3'. I figured that framing as 3 separate would require more king studs which would split the windows even farther apart. That's a non-starter because I want the group of windows to act as a single source of light.
But, here's a 3-opening version anyway. Better?
Center window RO is 4'.
Left and right window ROs are 3'.
Tiziano,
Even if you use a continuous 11'-0" header, the span is effectively broken into three sections by the intermediate framing, so both the size of the header and number of king studs at the ends can be reduced.
You can simplify your life and install by changing the windows to a 3 element setup, all the same size (so real 11" span for the opening). These can be connected together with joiners so there is no trim of flashing between elements. Instead and trimming 3 openings as is you have to do one single large one.
This also eliminates lot of the extra lumber you have there. Win/win on cost, labor and efficiency.
I've done it as Malcolm suggests, using multiple short headers for a row of five 3' windows. They were spaced 39" o.c., leaving room for doubled full-height studs between them. There was also a double king at each end; no jacks at all. The short headers were supported by Simpson header hangers. But run it by your building inspector first.
p.s. In the 2021 and 2024 versions of the IRC, table R603.7(1) relates to steel framing. Headers for wood framing are in tables R602.7(1) and R602.7.5, which make no reference to the stud spacing.
This discussion brings up a variant I saw on working drawings for my cousin's house. The first floor rim-joist had been doubled, and an LVL added on the outside of the raised-heel trusses, meaning there were no headers in any of the walls.
The upsides were that you could set the head height as high as you wanted, had less interruption in the cavity insulation, and moving openings around was as simple as moving studs.
You do need to add hangers to both the joists and trusses though.
Thanks everyone.
Reducing all this to a set of options, this is what I think I'm reading:
1. Do what I had in my initial image in the thread.
2. Do what I had in the initial image but:
- Run the jack studs full height
- Eliminate the plate below the header (and swap the rigid insulation to the back side of the header)
- Eliminate the jack studs under the windows
3. Split the windows into 3 separate headers (my second image in the thread) but:
- Run the jack studs full height
- Eliminate the plate below the header (and swap the rigid insulation to the back side of the header)
4. Change the windows to a single, three element and uniformly sized assembly. Trim as such.
5. Split the windows into 3 separate headers and:
- Run pairs of full height jack studs between the windows
- Hang the headers with Simpson header hangers
- Double king studs at the far ends of the group of windows
Attached is an update, largely using #2.
Assuming it's valid, another advantage it gives me is complete 16" OC across the wall. This should help when I attach the Zip-12 sheathing.
Since the structure is <200 sq ft no inspection is needed in my area. But, I do want to build it as if it was.
Tiziano,
That works. You don't need two jack studs at the ends of the beam though. The ends are carrying half the load the two sets inside them are.
Thanks Malcolm.
I would do away with the continuous header. One king with a jack at each end and a king sandwiched by jacks between the windows.
Unless you have an aesthetic concern with 3 studs between the windows rather than two this would be a stronger wall and easier to build.
I'd minimize the header size. Those openings look like a single 2x6 might be enough. That depends on what's happening above. If this is the lower level of a 2 story wall and you have a rim board above that wall the rim board could serve as your header and you could do away with the headers above the windows entirely. More lumber savings and better insulation.
If you used a rim joist as header you could just do double kings at each end and between each window and do away with the jacks entirely. That would give you 8 kings. Well more than enough for the job. But a fussy inspector might want an engineer's input at that point. But that's probably how I would detail it.
If they were "my guys" I'd tell them it's time to learn a new trick and frame 24" o.c. There's no excuse not to anymore.
Nothing above.