How to Size a Header: Lumber, LVLs, Jack Studs and More

Added: 2026-05-31

[00:00:00]Hey guys, in this video we're going to be going over sizing headers. So, picking the board up top, whether it's a 2x12, 2x10, or other. Um, how many plies of that board that we need to carry the strength to carry the weight down and how many jack studs or trimmers we need on each side of the window underneath the header to support it.

[00:00:26]There's quite a few different ways of building a header. Um, we'll go over three of the ones that we most commonly use. Imagine all these pictures as if it's just a cross-section of the wall.

[00:00:36]So, if you cut the wall in half and we're actually looking at the pieces going down the side. So, if these are 2x12s here, um, this is probably the most common way of building headers is we just nail them together. uh we put a 2x6 on the top and bottom and then these will be the upper cripples connecting or transferring the weight from the double top plate down to the header. Then right below this 2x6 we have our jack stud here or a trimmer stud. So this effectively brings the weight down through the top plate through the upper over the sides of the window into this trimmer stud. Another way of doing this is to just run this board short and run this trimmer all the way up to the bottom of the 2 by12s.

[00:01:27]Uh it's just a better load transfer in that scenario, but either way is fine as long as it's tight. Uh second way, the way we're doing it on this job is we have the same setup, double top plates, upper cripples, and then instead of nailing these plies together, we are building a box header. So, we have a 2 by on the outside and inside of this header, and then we put insulation in when we build it. So, in this case, the bottom 2x6 that holds this box together sits directly on the jack studs. Um, this this way is nice for it's already insulated. Um, some builders prefer it.

[00:02:10]And when you're building headers this way, you need to make sure and keep this gap to the inside of the house because you're going to get OSB covering the outside and they need to be able to insulate this section. Um either way, you need to allow for insulation. Um the third and final most common way that we we build headers, we do this usually when we're only using LVL's. Um it's just a higherend build. We will butt the LVL's. We'll number one nail them together. Then we'll butt them right into the double top plate so they'll load transfer. There's no upper cripples involved. No upper uh 2x6 on this header. And then these sit directly on the jack stud. So this is my personal favorite way of building headers. Not because it's the quickest or easiest, but the load transfer is the best because you actually you only have a couple connections in here that you have to get very tight instead of like four or five connections. Um, when you when you have this, there's so much room for uh settling. When you get 53 seconds, that's over an eighth. And that allows, you'll see it in lots of houses, there's drywall cracks that come off the corners of the the upper corners of the windows.

[00:03:35]That's because that it's not cuz the house is falling down, but all of that header area above the window is is moving down, settling a little bit.

[00:03:45]Everything's compressing, whether there was gaps when it was framed or it's just the wood sagging, all all sorts of stuff. and it will pull that piece of drywall down and it'll crack off the upper two corners. Um, so this way, just because it has the least connections possible, um, is my personal favorite way of doing load transfer around a window or door.

[00:04:07]When we're doing it this way, the reason it's so much more work is cuz the top of the window is usually way lower down.

[00:04:16]So, this is where the actual RORO of the window starts. Um, so this means we have to fur down with upper cripples below the header and then put either a single or a double 2x6 uh on top of the window. So this builders request a double sill, double window sill and a double header like this uh to allow for better trim. Uh the trim is just nailed on a lot lot tougher on these higher quality homes. Um, the other reason I really like doing the headers this way is because if the window needs to be resized, um, moving moving the actual window up, whether they're putting a countertop or a bench or desk or something in there or they're just changing the height, then we can actually cut these out and move it all the way up to this header without having to redo the whole deal. Um, which saves a lot of time. It's like maybe once every three houses something like that happens. But, uh, it's just so convenient. Plus, it's a better load transfer. So, this is my favorite way, um, personally. But, we we do whatever the customer requests. And on this job, we're going to be showing you uh, this insulated box. One more thing on this, when we build this insulated box this way, as you can see, this is a two ply, one two pies of that 2x12 or 2x10 uh, structural component. If we need to add a third ply in here, uh, we'll just nail it to the one on the outside. So, you'll still get insulation in there. There'll be a double ply on the outside and a single ply on the inside, but that counts as a triple ply header in this case. Um, obviously, you can only fit up to a triple ply 2x 2 by whatever in a 2x6 wall. If you need to go to a four ply, you're either going to have to step it up to a 2x8 wall or go to an LVL header. Okay, so just to go over kind of the basics of what exactly headers are doing and where we're where we're thinking about putting them in.

[00:06:20]Obviously, it's to carry the weight above a window or door opening down and to the side so that it doesn't go through and crack the glass. Um, so on this end of the house, this is only this is the final story here. We got a basement and then the roof trusses go right above me. There's no second floor here. So on these sidewalls, because the trusses are spanning this way, they are carrying the weight of the roof. So they're carrying the dead load, the snow load, uh everything here um is going into these side walls. This end wall here is a gable end. So it has one truss. It's spread out very evenly through the wall. There's basically no weight on any of the openings over there. Uh on smaller openings on a gable end, um we nail a board to the bottom of the truss uh way up in the attic because it it's just carrying so little so little weight. On a on a gable end, we'll put a header in when it gets to be like six maybe 8 foot wide. Uh anything 6t or over. then you start wanting to uh put a header in a gable end just because the actual span will allow it to sag over time. But as far as weight carry, there's there's just nothing going on in a gable end wall. Any walls that the trusses are perpendicular to that wall.

[00:07:47]We we really want to pay attention and that's what this video is mainly going to be covering is how we pick the correct size of header for these openings. just to give you guys a visual of what I'm looking at here. Um, we got a 3D viewer. Uh, so if you hop on my phone with me, you can see this whole end of the house here. The trusses are running side to side and we just have a gable end. We do have these couple of beam pockets here, but they are not on our openings. Um, they're going to be in between and on the end edge of our openings. So all this this weight from these trusses is coming down through this wall and that is why we need a header. Okay, coming over here to the other side of the house. Um this is a little bit different layout. We have a second story above us. So we have floor trusses running this way and then we also have roof trusses running this way.

[00:08:42]So these sidewalls here are carrying a lot more weight. It's the live and dead loads on the second floor. live and dead loads on the roof trusses above. Both coming down through these walls. Once we get to the second story, it's only the roof load coming down through those walls. And in the basement where we did the intro, you could see it had a triple jack, super beefy header. one was LVL because not only does it have the roof trusses coming down through that wall, the second floor trusses, but it has the first floor trusses as well, which in this case are getting these are getting jiprete on top of them. So that almost it it almost adds a second floor. Um it a normal floor live load is about 40 lbs per square foot and Jipe adds I believe it's 30 35 lbs a square foot on top of that. So the headers on these walls underneath us are carrying three floors, two floors. One has jibcrete, so a lot of extra weight, and the snow load up here. Um, which we're pretty high up, so we have a decent snow load here. So this is this is kind of what you're thinking about when you're laying out headers is where is the load coming down through?

[00:09:57]Over here on this end, we have just another gable end. There's a tiny little deck coming off of it. that we'll be putting on later this year. Um, but that's it. Other than that, it's just a a ladder truss and a gable truss.

[00:10:12]There's barely any weight. So, these headers aren't as uh beefy as these ones uh over here and especially downstairs.

[00:10:19]I'll show a 3D viewer of this so you can kind of see what I'm talking about.

[00:10:22]Here's the side of the house that I'm standing in. You can see the roof trusses are going front to back. Floor trusses are going front to back. Uh, same with that main floor that we're standing on and then the basement.

[00:10:35]There's that final wall carrying all three layers. When we're picking our header sizes, as you'll see with the code book, the main thing we're thinking about is the actual square footage coming down on that header. So, the two factors we're dealing with are the width of the opening because the wider the opening, the more floor and roof it's carrying, and then the width of the building. Because if you have a twoft opening and the building is 10 ft wide, it's not carrying a bunch. But if the building's 100 ft wide, that it's carrying 100 ft that way of trusses coming down onto that header. So, it's way different. So, width of the opening, width of the building. The little nuance in that is with floor trusses, especially if they're clear span floor trusses, meaning they're going the whole way from exterior wall to exterior wall or if they're center bearing. So, in this case, we're not quite center bearing, but you can see these red chalk lines here in the ground. They indicate a beam in the floor truss system up above me. So, these trusses don't quite go all the way. Uh they they actually split here, which means it's only carrying half of the weight. So, when we dive into the code book, you'll see how all these little pieces fit together.

[00:11:57]But, uh just to show you that beam, um if I take off the roof trusses here, um there's that beam I'm talking about.

[00:12:07]This is in the floor that is above my head that isn't built yet. actually carrying these trusses. Uh if I can click on a truss, maybe there's a truss. It's spanning from the wall on my left over to that beam. Not all the way across. One more thing I want to cover is these jack studs that go on the side here. So, what are they for and how many to put underneath and why?

[00:12:35]Um, so a lot of people think that when you have to add a jack stud, it's because this one, just one of them isn't strong enough, but it it's actually one is plenty strong to carry a ton of weight, especially when it's nailed to a king sheetated everything. The reason we add two is because of compression.

[00:12:58]So this part of the 2x6 is actually weak. So, if we have the whole thing on this little tiny surface area and we have a ton of weight here, it will actually squish this board down.

[00:13:13]Um, the the jack stud won't squish because this is endrain. Uh, you can see pretty easily like if I if I hammer this, I can make a dent. But if I hammer the end of the jack stud, the dent is so small compared to the dent on the side of the wood because it's endrain. It's way harder to compress. So again, the reason we would add two or in some cases even three jack studs here is just because the weight is too much for the little surface area of one. If you guys are getting any value out of this video, please consider subscribing because we're doing a video about every skill it takes to frame a house. The last variable when picking header sizes is snow load. Um, dead load on a floor trust system is usually the same. The code book uses those same numbers for most residential houses, but snow load depends on your area and your elevation.

[00:14:11]On this house, I'm using what the engineer used for snow load, which is a ground snow load of 56 lbs per square foot. Um, even looking it up on Google for this location, it spit out the same thing.

[00:14:25]We're going to be walking you guys through two examples here. We already did the headers, but we're going to be going through the examples so you can see how we use the code book with the span the header span chart to decide these sizes. So, uh, you can you can do this way before you get your walls laid out and have all of this already prepared. Um, we often end up doing it right when we lay out. It's just easier to decide the number of jack studs. You can count exactly how many cripples you need. Uh, the cut list just goes smoother and it's something to do. So, coming over here, we just have the roof trusses on these walls. Uh, no floor trusses above us. So, we have our window arro written here. So, they're a rough opening. It's about 60 in wide, 5t wide.

[00:15:12]Um, and the height does not matter. It could be a door. It's the same thing as a window because all we care is about the width because that's how many trusses it's carrying. So, we have a 60-in wide window and we have a 26 ft wide or deep building. So, that's essentially the load that's coming down through. And you could even calculate that out. you go uh the width of the window multiplied by the width of the building and then only half of that is coming down on this header. The other half is going to the other side of the wall. So let's bring it to the code book. Okay, we're using the IRC21 2021.

[00:15:53]Um this is this is the chart we use 616 617 um for picking headers usually unless the engineer calls out a beefier header or uh the builder's already spec everything. Here's the main chart. We got four different or five different uh layouts for the building. None of these include a gable. A gable has no weight relatively. So that is that is irrelevant from these charts. The main thing we're looking at here is what we're talking about whether it's carrying roof trusses uh center bearing floor trusses and roof clear span floor trusses and roof and then we go up to a third uh story with those two iterations as well. So, we got to first thing is to find what we're dealing with, which in this case with the example we just went over, we're dealing with just the roof and ceiling.

[00:16:54]So, this is the drywall, shingles, snow load. That's it. So, then we're going over to the snow load. This is our ground snow load. In this case, we are uh at 56 lbs per square foot. So, they they only have 30, 50, 70 in here. Um we're going to focus on these two to uh choose the proper size of header. Uh it's somewhere in here. But this column, each of these columns are respective to the snow load above. There's no in between in the code book. So if we come down here, we got our snow load, we got our our header location, and now we have building width. So, in this case, we're a 26 ft wide building um with a 56 lbs per square foot. So, we're going to be looking in these two columns.

[00:17:50]Um, and because we have 2x12's on site, I'm just going to come down to a twoly 2x12, which is this size of header all the way over here. And we're going to follow this across to a 50 lb snow load, 24 foot wide building. We can go up to 6'11 for 70 lb per square foot at 24T wide.

[00:18:15]We can go up to 6'2.

[00:18:17]So these are our spans that our window basically the width of our window when the building is this wide. And technically our building is a little bit wider than 24. It's a little more than 50. But between these two numbers, uh, our 5-ft window is easily carried by a twoly 2x12. So, this is a lot of information to sort through, but basically once you have your variables, which is where your header is located on this far left, your ground snow load, and the width of your building, then you can choose between all these different header sizes, whether it's a one ply, two ply, three ply, four ply, and then you go all the way over to see the span that you're allowed to to cover, the width of the window. Um, right next to the width of the window is the number of jacks. That's what this is right here.

[00:19:16]Number of jacks on each side of the window that's required. So, when it says one, that's one on each side. When it says two, that's two on each side. Um, you can see there's very few places that uh get all the way up to three jacks required. So, with a two ply 2x12, a five foot window on a 26 foot wide building is uh totally doable. We could go all the way up to like six over six feet. 6 foot two is fine with a 70 pound snow load. Um, two jacks. Obviously, uh, building inspectors sometimes have rules of thumb where they anything 5t or over wide, they want two jacks on. Some even say it's on a gable end. So, uh, definitely know your area, know your building inspector, ask around, see what what they like there. But this this is the code book. Um, and it doesn't hurt to overbuild it. Let's go over to the that other side where we had two stories and a center bearing floor to do another example. Okay, here we are on the other side of the house. Um we'll show you on the 3D viewer. Uh if you can see right here, we are in this little wall right there. So this is carrying a floor trust system which is center bearing. And you can see it's not actually center bearing. It's way closer to the wall that we're framing. Um, but we're going to call it center bearing. That usually things don't fit exactly to these numbers. You kind of have to go between two categories and make a best case. And don't worry, always oversize it if you're unsure. Uh, overbuild it if you if you're if you have any doubts.

[00:20:58]Um, but on this 3D viewer again, we have roof trusses. Our building is 28 feet wide right here. Uh spanning all the way.

[00:21:09]Um so yeah, let's dive into this code book. Okay, so again, coming over on the left first, we have roof, ceiling, and one center bearing floor. So even though we're carrying a little bit less than this, we're still going to this section.

[00:21:24]We're going uh between these two or about 56.

[00:21:29]So our building's 28 ft wide. We're somewhere in between these and we're going to check out a 2x two ply 2x12 because that's what we have on site. So when all these factors come together, uh for a 24 ft building, we can span 6'2.

[00:21:48]Um for 70 lb, we can even go 5'8, 36, we're still over uh 36t wide, we're still over 5t, which is what our header is here. Um, but either way, we definitely want to do at least two jack studs on each side and a two ply 2 by12 is going to work fine for this header location. Like I mentioned, I like to do these header calcs uh when we're laying out um and make the cut list as we go.

[00:22:18]One of the reasons is I can just see the house a lot better. I don't have to go through the plans a bunch and hopefully the trusses are already decided and stuff like that. You can do it offsite, but this is how we do it a lot of the time. Um, right here we have uh we label our windows A through Z uh going around the house. And when we're laying out, we write the actual RO of the window right by the center of the window that we get from the plans. So, this is the first thing that's done. Someone just goes around, marks centers, and writes the RORO. Now, just like we mentioned in the layout video for laying out plates, the RORO, at least our company policy is we always get it off of the window order.

[00:23:06]We do not take it off of the plans. Even if even if the general says the plans are good, they've updated the RORO's. Uh it's just best practice to take the RORO's off of the window order themselves. Um there's there's always mistakes. Always mistakes. So, um, RORO goes right here. And then when we're making our cut list, we first have to know how many jacks because if we add two jacks, we can't bring those into the window. That's very important. We have to add those jacks on each side of the RORO. And then between the jacks is our final RORO for the window. So, after we've marked this out, we go around do header calculations. And then we add our jacks on each side. put our king stud and then we're able to add if in this case we have two jacks on each side. So that's three inches a total of six inches that we would add to this number in order to get this header length. So that goes on the cut list. Uh window A, here's the RORO, here's the number of jacks, here's the header length. So then we're able to cut and build all these correctly. It's also very nice to have that uh twostep verification when doing layout. If someone makes a mistake or they put the jacks inside when you're building the wall, the header will be too big. So, it's easy to catch that mistake. Um cuz if you have to tear if this window doesn't fit and you have to tear it apart and make it wider, it is terrible. Uh it's the worst. Um, so yeah, really make sure that you get you do your math right, you pay attention to that code book, you pick the right header, and add the right amount of jacks. I just wanted to give you guys another example of how this stuff all goes together. Uh, above me here, this is below that singlestory section that we are doing the headers on. So, the roof trusses are running this way. Um, but down here, we have these headers are under the floor and roof because we're in the basement. But since the floor trusses are running this way, these headers are not carrying the weight from the floor system, but they are carrying the weight from the roof system. So it's you just run this header the same as if it was just carrying a roof and no floor because there's no floor coming down onto this header. As you can see, we got a double ply 2x12. We got two jacks on each side again to reduce compression.

[00:25:44]it has enough surface area so that 2 by six doesn't compress. Um, right here we have an even narrower opening. Same exact deal, but we have three jack studs on each side. That's because we have a huge deck beam running all the way to the corner and a huge porch roof beam pocketing above that. So both of them are coming down through the wall, through the floor, and into this header and around the sides. So you're really thinking ahead about the structure when you're building. Even down here, the very first walls you built, you're thinking all the way up what weight is coming down through. As you can see, we have our uh point loads in the floor system already. uh we do need to add a bunch more upper cripples uh under that point load in order to get it down into the header. This video is mostly about exterior headers and building and sizing them. But uh just to touch on interior headers as well. Um here we have this is a loadbear wall, an interior load bear wall. The floor trusses bear halfway on it. So that's why we have this 2x8 here over this. Um, it's very rare you would need two jacks on an interior uh interior header, but it it does happen.

[00:27:07]Coming over here, you can see this is a nonloadad bear interior wall. It's running parallel uh with the floor trusses, and it has no no header in here. This this double ply 2x4 is just for trim, just so the trim nails on nice around it.

[00:27:25]Um, if if an interior wall is running perpendicular to the trusses, it doesn't always mean it's lowbear. And if it's running parallel to the trusses, it doesn't always mean it's non-loadar.

[00:27:37]Sometimes we will have point loads coming down through these walls uh that it needs to be structural or there is a footing underneath it. This is a unique scenario here. We have I believe this is a 12t wide patio door.

[00:27:53]And as you can see, we have LVL's up here. This LVL was actually specked out by the truss supplier. Um, anytime they get a wide opening, the truss supplier tends to speck out those. This is actually a gable end. So, it's it's not carrying any of the floor system. It's not carrying any of the roof system, but it is carrying a very large deck over a very wide span. So, this not only is it carrying a deck, but it just has to also span this far, which is a big factor in sizing headers. If you need to upgrade to an LVL because it's not in the code book, you're probably going to have to get an engineer involved. As you can see, we only have two jack studs here.

[00:28:35]Even though this window's way bigger, or this door is way bigger than that other door over there with three, it's just not as much uh there's barely any square footage on it of roof coming down through this header. Also, because the door is so wide, we have two king studs on each end, and that just stabilizes the header. Uh, if there's any wind force on it, um, going through the building, it keeps the header from potentially rolling at all. Just for fun, check out this curved staircase behind me. Um, these this is our first time doing a curved loadbearing wall.

[00:29:10]So, we have two stories of loadbear.

[00:29:14]These wall these curved walls are carrying the floor through it. So that's why it's it's not exactly a header, but it is carrying a decent amount of weight down through these top plates. That's why we have a triple top plate with a layer of Advantec in there. Um just a super cool detail on this house. Here's uh the one scenario where we needed to put an LVL in ourselves because um a a triple ply 2x12 did not cover the weight that this window was carrying. This goes up to that second floor that we were on that had or the main floor that had the second floor above it with a 28 foot roof span plus the floors getting jiffrete. So that's why we ended up putting in a 11 and 7/8 lvl with a triple jack on each side. Um there's just so much weight.

[00:30:06]It's basically three floors on this with the Jipe. Um plus a pretty high snow load. Thanks for watching and be sure to check out our next video of how we place the window as far as height. So, windows can go all over the place. This is going to be how we read the plans, how we get the lengths of our jack studs here in order to set our header heights.

[00:30:29]>> I kind of pointed Yes.