Garage Door Headers
Garage Door Headers
(OP)
Usually when determining the size of a header for garage door I typically only consider the gravity live and dead loads acting on the beam about its strong axis and then plug them into the beam calculator here:
Medeek Beam Calculator
Most residential garage doors attach to the vertical jambs of the door so any wind loading will not be seen by the header but by the jambs which is picked up by the king studs at the sides of the door. However this is assuming that the pony wall above the header is non-existent or relatively short. What I am wondering is what about a garage door at the gable end of a building where the possibility of biaxial loading might become more significant. A properly built structure should have some form of lateral bracing about every 10 ft o/c for trusses but I have seen plenty of construction out there that seems to neglect this important detail. As such the wind loads (C&C) on the gable end will be felt by the garage door header and sizing of the header may be affected by this increased biaxial loading situation D + (.6W) or D + 0.75(0.6W) + 0.75(S).
I am looking for any white papers or other resources on this topic as well as any comments or experience dealing specifically with wind loading on garage door headers.
Another possible loading configuration is when the double top plate is missing and the beam serves as a collector. In this case we have bending and axial loading, however this situation would not seem to be as common.
Medeek Beam Calculator
Most residential garage doors attach to the vertical jambs of the door so any wind loading will not be seen by the header but by the jambs which is picked up by the king studs at the sides of the door. However this is assuming that the pony wall above the header is non-existent or relatively short. What I am wondering is what about a garage door at the gable end of a building where the possibility of biaxial loading might become more significant. A properly built structure should have some form of lateral bracing about every 10 ft o/c for trusses but I have seen plenty of construction out there that seems to neglect this important detail. As such the wind loads (C&C) on the gable end will be felt by the garage door header and sizing of the header may be affected by this increased biaxial loading situation D + (.6W) or D + 0.75(0.6W) + 0.75(S).
I am looking for any white papers or other resources on this topic as well as any comments or experience dealing specifically with wind loading on garage door headers.
Another possible loading configuration is when the double top plate is missing and the beam serves as a collector. In this case we have bending and axial loading, however this situation would not seem to be as common.






RE: Garage Door Headers
RE: Garage Door Headers
RE: Garage Door Headers
What about when they only want 2x4 stud walls? Then your three ply doesn't fit in the wall.
For me it's a situational call. If I can fit a 3 ply header then I
neverrarely check it. I have had one or two instances where I have needed to add members on the flat above and below the header to improve the weak axis resistance, but it isn't common.RE: Garage Door Headers
Mike McCann, PE, SE (WA)
RE: Garage Door Headers
RE: Garage Door Headers
I make them use a 2x6 wall when I feel it is needed. They usually do not complain. It is a very small area to frame.
RE: Garage Door Headers
RE: Garage Door Headers
Ah, yes.
RE: Garage Door Headers
It's not that I wouldn't want to go check. It's that for residential work it isn't required by the AHJ. And without me constantly calling to find out construction progress I wouldn't know when to go.
Do you have time each and every day (possibly multiple times each day) to be calling each contractor working on your active projects to check up on construction progress? I know I sure don't.
On the jobs where conformance reviews are required the contractor is required to contact me at certain stages of the construction. On jobs where no review is required the contractor doesn't want to hear from me.
RE: Garage Door Headers
Every house around here is inspected by the county and they will usually catch deviations like that. You can't get hooked up to the grid without it.
I am rarely called to inspect my designs, however.
Many custom houses in our area are going to 2x6 walls anyway, so it is not much of an issue.
RE: Garage Door Headers
RE: Garage Door Headers
The fastest way for a project to go sour is to put in a bunch of details that deviate from standard practice. However, as you say, 2x6 garage walls are becoming much more prevalent. Especially with everyone wanting a heated garage.
RE: Garage Door Headers
WTCA has some recommended detailing that theoretically braces the wall/gable truss joint: Link
I have a dream for solving Medeek's very issue. It's a dream that will never come true but, what the heck, here she is:
The greatest trick that bond stress ever pulled was convincing the world it didn't exist.
RE: Garage Door Headers
RE: Garage Door Headers
RE: Garage Door Headers
RE: Garage Door Headers
Diaphragm aspect ratio limits would apply to the plywood solution but not the truss solution, right?
The greatest trick that bond stress ever pulled was convincing the world it didn't exist.
RE: Garage Door Headers
For the gable wall situation A few thoughts.
1. I do like the truss idea and I've used something similar.
2. I see kickers up to the rafters many times which isn't bad but almost always calcs out to overstress the rafter.
3. Usually the ceiling is drywalled so you have a diaphragm and also there is some sort of stiff back bracing the bottom chords which 'ties' together the opposite gables and distributes the load.
4. I'm sure the wall acts as a plate elements when fully sheathed.
EIT
www.HowToEngineer.com
RE: Garage Door Headers
The greatest trick that bond stress ever pulled was convincing the world it didn't exist.
RE: Garage Door Headers
RE: Garage Door Headers
1) LVL absorbs whatever gravity loads are tributary to it. Check.
2) When chord forces develop, they are shared between LVL and top plates in proportion to stiffness and fastening. Check.
3) LVL, which is now a beam column, fails due to overstress and crushes innocent family in front of fire place. Doh.
4) Properly designed top plates are still adequately designed for any chord forces that may develop in future. Check.
Does this ever happen? No. Do things like load casing and composite behavior help? Sure. These things aren't the point however. The point is that beams can't simply be told not to accept undesirable axial loads. They, like me, are rather poor listeners.
The greatest trick that bond stress ever pulled was convincing the world it didn't exist.
RE: Garage Door Headers
I think as engineers we make alot of broad brush assumptions, some of which probably work just fine, but what is really going on with the structure. Obviously for practical reasons such FEA simulations are prohibitively expensive and time consuming for most residential work.
For instance if you have a large gable wall full of windows (beach house design) with a rafter roof. An FEA approach might be appropriate given the complexity of the wall and the high wind loads. In this sort of situation the biaxial bending of the king studs and any beams spanning the windows would be significant in my opinion.
RE: Garage Door Headers
What about if you specified no nails between the header and the top plate? (I'm totally just playing devil's advocate here and suggesting a situation that is highly unlikely)
Would you still assume the header takes the axial load?
RE: Garage Door Headers
@Jayrod: I would not assume axial load in that scenario. Although some amount of axial transfer would still come from... wait for it... SHEAR FRICTION! This is your fault -- you baited me into this.
I've been working on something related in my head for some time. I think of it in steel but it can be adapted to this. Assume that:
1) I've got a header that can handle all of the gravity loads that it will be exposed to.
2) I've got a top plate assembly that can handle all of the axial loads that it will be exposed to.
3) Horizontal shear transfer between header and plate assembly is a given. 100% composite behvior.
Is there any rigorous way to say that the composite section is acceptable for the combined loading without doing a beam column check on the composite section? My gut tells me that everything is indeed fine. I can't prove that though.
The greatest trick that bond stress ever pulled was convincing the world it didn't exist.