Header Span Table Questions
Header Span Table Questions
(OP)
Good Morning All,
I'm from NY (PE-Civil). I am doing some design on my own attached garage and I am a bit stumped on my garage header as far as prescriptive code is concerned. IT doesn't appear that the prescriptive code accounts for openings larger enough for the 16' doors? Must these be an engineered beam, or spec's by LVL/Glulam, etc...
Thanks all for the help.
I'm from NY (PE-Civil). I am doing some design on my own attached garage and I am a bit stumped on my garage header as far as prescriptive code is concerned. IT doesn't appear that the prescriptive code accounts for openings larger enough for the 16' doors? Must these be an engineered beam, or spec's by LVL/Glulam, etc...
Thanks all for the help.






RE: Header Span Table Questions
You need a local Structural Engineer's help.
RE: Header Span Table Questions
I wouldn't call myself a "structural" engineer, but I do have a great deal of experience in structural design and analysis I am a NY PE (Civil). I just don't have much experience in residential design. I could sit here and design a beam specific for the overhead door, but I know that we have prescriptive code in place that handles the vast majority of residential specification.
It appears that most people use LVL's in this scenario (keeps engineering costs down I assume, and transferrs liability to LVL manufacturere and sealer/stamper) but I was hoping for somebody to shed a little more light on the process or alternate methods. I am a PE and I do have experience in the analysis; not just a homeowner posting a question on here.
Thanks all. I appreciate the help.
RE: Header Span Table Questions
Here in Phoenix, most 16' headers with 2' max roof trib (gable end truss condition) are (2)-2x10 or (2)-2x12.
RE: Header Span Table Questions
I'm probably going to spec an LVL, but I really wanted to see if there were any other options (i.e. built up 2x12's won't make the 16 ft).
Thanks all
RE: Header Span Table Questions
Be aware of the recent discussions regarding LVL deflections, there may be inferior product made by other companies.
RE: Header Span Table Questions
RE: Header Span Table Questions
http://www.woodbywy.com/software/
RE: Header Span Table Questions
My real motivation here it to figure out how it is accomplished. Before composite materials was there not larger openings, or where they always steel?
Thanks again
RE: Header Span Table Questions
I see a great deal of steel beams doing this in older houses.
RE: Header Span Table Questions
Appreciate all the help.
RE: Header Span Table Questions
The tricky part of a garage is making the garage door walls/jambs work laterally and for in-plane shear, especially if the garage door(s) eat up most of the wall.
CELOttawa- Interesting comment about regional structural systems. I have never seen a steel beam used as a residential header in Florida, wood or CMU only. Rarely see steel at a house period, of course we also rarely have basements.
RE: Header Span Table Questions
In fairly low-seismic areas like NY I understand in-plane lateral shear is not a big issue, assume 3-sided diaphragm but ignoring the stringent Code reqmts about diaphragm ratio and diaphragm deflection etc, as we mostly do here in Phoenix area.
RE: Header Span Table Questions
Actually New Zealand had fairly similar construction techniques to Canada, but was architecturally very different. Australia surprised me by having a great deal of residential load bearing masonry (clay brick). Haven't seen that in a building built in Canada since 1920.
RE: Header Span Table Questions
RE: Header Span Table Questions
Mike McCann
MMC Engineering
RE: Header Span Table Questions
I don't know of any practicing structural engineer who uses beam span tables. I'm not saying that they can't be useful but I am saying that if that's what you're relying on to proceed with caution. I wouldn't try to do civil or environmental engineering even though I work with people in those disciplines rather often. The problem would be, though, that I don't even know enough to know how much I don't know. I could get myself into trouble and not know it.
Some years back I reviewed drawings for some high-end residential structures. They had some very large and inefficient beam sizes, on the order of W10x54, maybe larger. Wondering why they used such a silly beam size I ran the numbers whereupon it became obvious: the designer apparently sized the beams from the moment capacity chart in the steel manual but didn't realize his beams were braced. I'm guessing the architect sized his own beams. The worst part was that this was a development so those beams sizes were repeated many times over. So, by saving a few hundred or a few thousand dollars by not hiring a structural engineer he cost many tens of thousands of dollars on inefficiently sized beams and unnecessarily-difficult installation labor.
But then, I suppose it could have been worse: he could have undersized them...
RE: Header Span Table Questions
RE: Header Span Table Questions
Are you referring to live load deflection or total deflection?
RE: Header Span Table Questions
RE: Header Span Table Questions
I will vary from this if the job is clearly going to be able to sustain more movement, but rarely. The number one complaint one hears these days about all the McMansions is the lively floors and crappy roofs. I want our work to stand firm.
RE: Header Span Table Questions
Also, longer header beams where exterior wall is stucco. A beam w/ L/360 total may be adequate for a 16' span, but create a problem with a 35' span.
RE: Header Span Table Questions
RE: Header Span Table Questions
Back in the day, the vast majority of garage roofs were gable end roofs with the truss bearing on the walls not containing the 16' door. They were often constructed with 3-2x10 and, while likely not kosher by the numbers, seem to have been serviceable. Who knows, maybe the roof framing held up the header somehow.
Even in NY lateral will be an issue for the wall segments either side of the door. Think hurricane.
The greatest trick that bond stress ever pulled was convincing the world it didn't exist.
RE: Header Span Table Questions
I was just suggesting additional considerations in a general sense for application in any other project.
It was implied, but you are right, it did sound a bit like I was contradicting you.
RE: Header Span Table Questions
Yes you are generally correct, but I now do so many custom, wood constructed houses, for me it has become quicker overall to use my Excel workbook to churn out all my designs. The way it is set up, it makes it easier to just run the uniform loaded beams along with the beams with complex loading.
I am not saying everyone should be able to do this, I am saying it as advice for someone wanting to streamline the design process.
I use to submit a sheet or two with tabulated beam designs, ie B3, B7, B8 are 2-2x6 and B2, B13 are 2-2x8, etc, which was fine, but the way I set up my Excel shows 4 beam designs per sheet and showing simple uniform load desiogns along with the more complicated case works a bit better for me.
RE: Header Span Table Questions
The demolition contractor started knocking down the right elevation wall (the house was rectangular in plan, longer in the left-right direction than the front to back direction), but leaving the roof. He got about 1/3 of the way into the house as he was knocking down the front and back walls alternatively, all the time the roof was cantilevering and sagging, then finally the unsupported roof collapsed. It made a more efficient demo because he didn't waste any time thrashing at the roof.
RE: Header Span Table Questions
RE: Header Span Table Questions
RE: Header Span Table Questions
Years ago, before plans check, the tract home builders were always insisting the headers be 2-2x10, and those did sag a little.
RE: Header Span Table Questions
ps - for 8' plate height tract house, always 2 jack studs and 2 king studs, whether 2x4 or 2x6. If I took the time to design the kings per IBC 2012, the king probably wouldn't calculate, but I am of the opinion that the 2 lightly loaded jack studs, being just 1' short of the wall top plate, stiffen up the king studs considerably.
RE: Header Span Table Questions
I guess I wasn't thinking of things like lintels, precast planks, etc. Yes, I use tables for the likes of them too, as well as for metal decking, bar joists, and sometimes other types of joists as well. But I never use span tables for beams or girders. For such as that I always want some type of documentation of what loads I applied to it and what unbraced length I used. I.e., I would like to be able to check my files and quickly see whether the member in question carries a point load, a line load, does it carry a masonry veneer, etc. If it's guaranteed to include none of that then sure, a table will work, but I'd still rather have the full documentation. And yes, I have Excel spreadsheets and other software to help speed the process along.
What scares me, though, is the thought of people consulting span tables without considering all of the loads or circumstances that may apply. Just my opinion.