Code interpretation/application: span, header, # of Jack studs
I am converting a porch to a room (one story, lean-to roof), which is 14’x23’. On each of the shorter sides, I have a (2) 2×10 continuous header, for three windows on one side and two windows and a patio door on the other side. At the moment, each end of each header is supported by one 4×4, on which the headers sit; the other ends are attached to the house but are also supported by one 4×4; there will be at least an additional 2×4 added as support. At each end, I can add more 2x4s (I could probably add another 4-5 of them if need be); so, the two ends of each header can be very well supported.
It remains to be determined how many jack studs I need for each window and the patio door. I know that the 37” windows require only one jack stud. The other window is a 73” double, and the patio door is 72”.
When reading table R602.6(1) of the ICC (see attached screenshot), I am not sure whether is should apply the prescriptions for “buildings” with a width of 12’ or 24’. If I consider that my wall is 14’, and apply the prescriptions for 12’, I could have a (2) 2×8, or even (2) 2×6 header, in either case with ONE jack stud for each side of each window, including the 73” one; likewise for the patio door. If I apply the prescriptions for 24’ buildings (in consideration of the fact that the wall is 14’, hence more than 12’, or that the room, though 14’ deep, is 23’ long?), then I need a (2) 2×10 header and TWO jack studs at the 72”/73” openings. If I need two jack studs, then where the smaller windows flange the larger window or the patio door, I’ll end up having three jack studs. That’s something I can do, but I would prefer not to do, if not required.
What is the correct way of reading the code?
Thanks!
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Replies
Is the 14' wall or the 23' wall the eave wall, supporting the rafters? The "gable" walls don't have header requirements unless they are also the required shear walls.
Michael,
Thank you very much for your reply! The 14’ walls are NOT the ones supporting the rafters.
As for the notion of “shear walls,” I confess that it confuses me, and, so, I really don’t have an answer. The new room (previously a porch) is the usual rectangle attached on the side of the house—the 23’ side being parallel to the house, with the rafters, perpendicular to the house, resting on the posts and top plate along that side. The two other sides, perpendicular to the house, do not hold the roof’s weight. If course, if I understand the “shear” notion a bit (and I don’t understand it that much to be honest), those sides, as the my stick out from the house, are subject to lateral pressure from the house.
In any event, what does it mean to have “no header requirements”? (My headers are ok, by the way, in terms of width—they are of the correct width or exceed it. It’s the issue of the jack studs that I am uncertain about: I’d like to have just two 2x4s between the windows—or between the door and the windows—even if the opening for the patio door is 6’, and that for the double window is 6-1, on consideration of the fact that they are openings in the lateral, 14’ walls.
What do you think?
Yes, shear walls are for lateral resistance. With the addition attached to the house, there is no need for the addition's end walls to resist lateral forces. The eave wall does have lateral forces acting on it. The roof sheathing will help resist them but it's hard to quantify the contribution of the roof sheathing so engineers focus on walls. If the addition were a freestanding structure you would need to have a certain amount of required wall bracing: https://codes.iccsafe.org/content/IRC2015/chapter-6-wall-construction#IRC2015_Pt03_Ch06_SecR602.12.
I see your confusion about headers is cleared up below. To answer your question of why don't builders and code officials understand this, I wish I had a good answer. Some parts of building codes are pretty confusing or downright illogical, but this one seems pretty straightforward and logical to me.
Matt2021
Because the 14' walls are not carrying any of the roof load headers are not required. With no load on the headers jack studs are not required. Just box in the rough openings for the windows and the door. The 14' walls tie into the main house so shear should not be a concern.
Thanks, Eust2023! Coincidentally, I had just found the relevant code sections (see attached), but your explanation clarifies things for me. At this point I wonder whether I should have the (2) 2x10 header removed on one side; or will it be OK to still do the minimal rough opening for the windows, and not worry about the weight of the header I installed?
As for the opposite wall (again not-load bearing), as the header is too low for the door that has to go there, again, I wonder whether, rather than re-installing the header higher (clipping a corner of it to make it fit under the rafter), I shouldn’t just have everything removed, and some horizontal double plate be installed?
All of this raises the question: why did all the contractors who came out to look at the job talked about headers for those side walls? Why did the inspector at the township, looking at pictures and drawings, told me about headers? Those walls are NOT load bearing; and, if understand correctly, headers in non-bearing walls do NOT help with shearing strength; in fact, the opposite might be true.
This blog is INCREDIBLE. I wish I had posted my question months ago, before even applying for my building permit. On the other hand, why is there, in the “real world,” so little knowledge, so much confusion? It seems that what I ended up building is just a waste of lumber, a useless filler of space that could have been better insulated, and, now, a major nuisance (for the header that is too low).
Thanks again!!
Matt,
it's surprising how many people involved in building (including inspectors) don't understand the basic forces working on a simple gable-roofed structure.
The one justification for including lintels in non-loadbearing walls that makes some sense to me is that it can make future renovations and additions a lot easier. In most instances that's a bit of a stretch though.
Thank you very much, Malcolm! Indeed, mine is one of those cases in which future renovation (who h are very unlikely) will be made more difficult by the headers that I now have. For example, if someone, some day, wishes to replace some of the windows I am installing with taller windows, that unneeded header will only be on the way.
In any event, hopefully I’ll be able to clarify things with the inspector tomorrow, and just install two 2x4s between the windows. As for the header that, instead, needs to be lifted up, I guess I’ll just propose to remove it altogether, and maybe install a double top plate with 2x4s, and frame the windows and door under that.
Matt,
That sounds like a good plan. My favorite part of renovations is stripping away the un-needed and extraneous pieces. There is always a temptation to just leave what won't really interfere and get on with things, but it often comes back to bite you.
Whatever I'm building, I like to imagine a future occupant or contractor appreciating what they find - just as I do when I'm pleasantly surprised when I open up a wall or roof and see the care that was spent doing it correctly.
Malcolm:
That’s why I should have someone like you supervising the work ;-) Short of that, consulting with this forum is really helpful. I’ve learned so much since I discovered the site and its forum.
Thanks again!
Matt2021,
Good luck with your build!
Thank you very much, Malcolm!