Garage Door Headers 1

[medeek]

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.

 

[hokie66]

You seem to be only concerned about lateral wind loading. What about uplift?

 

[XR250]

I usually go with a 3-ply header on the longer spans and not worry about the out-of-plane loads. Never seen a problem.

 

[jayrod12]

Excel,

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 never rarely 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.

 

[msquared48]

Then use a 3.5" PSL or 3.125" Glulam.

Mike McCann, PE, SE (WA)

 

[bigmig]

Biaxial loading of a header on a large gable end wall is a reality. White paper or not, it is just a calculation that you definitely need to check. I designed a barn the other day with a gable wall that was so big I had to roll the header on the flat (gravity loads were basically wall self weight)to control deflections in a wind event.

 

[XR250]

@Jayrod;

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.

 

[jayrod12]

I wonder how many of the walls that were spec'd as 2x6 were framed as 2x4. I know around here if you deviate from standard sizing in residential work you have about a 50/50 chance of getting what you specified. That's mainly because there is no site visits to check conformance.

 

[Duwe6]

"That's mainly because there is no site visits to check conformance."

Ah, yes. If we don't care enough to go check something, how do we expect the construction folks to care enough to get it right?

 

[jayrod12]

Duwe6,

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.

 

[XR250]

@Jayrod;

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.

 

[ztengguy]

What do you do when you need it signed by a PE?

 

[jayrod12]

You are still relying on someone else to ensure the installation meets the design. If I can find a way around deviating from standard construction techniques I will do what I can to do it. That way I have a higher level of confidence that it will be constructed as designed.

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.

 

[KootK]

In my experience, this issue is endemic of both garage doors and large windows. Although headers in both applications often pick up biaxial loading, it's extremely rare to seem them designed for it. And still... no problems to speak of.

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.

 

[medeek]

Assuming that the correct lateral and diagonal bracing is used at the gable end truss (per WTCA documentation) then the biaxial loading of the header should be minimized and only the gravity loads need be considered.

 

[jayrod12]

KootK, Love the horizontal truss idea. I would think you could probably get it to work as a 22 1/2" deep truss that would fit in the first truss space. This would remove the requirement of an odd truss as the second last one.

 

[Duwe6]

KootK, this would also give some outstanding anchor points for multiple garage door opener brackets. Those tend to just be anchored to any 'ole truss. Mine is a 'hard ceiling' garage, so the sheetrock is transferring the stress to the adjacent trusses!

 

[KootK]

The oddball truss is certainly what keeps the dream from ever becoming reality. And garage door support would definitely count as a pro. Would this be more "saleable"?

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.

 

[RFreund]

For the window opening, I have checked out of plane and even axial when missing the top plate. I've also included straps to transfer the force.

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

http://www.HowToEngineer.com

 

[KootK]

I find it curious that we only worry about the axial load in the header if the top plates are missing. The reality is that the header and the top plates are fastened together and will experience approximately the same strain. The presence or absence of the top plates will affect the axial load in the header very little. It's analogous to the discussion that we have regarding strut and chord forces in composite steel floor systems. Are the axial loads in the edge angles or the perimeter beams? The answer is both of course.

The greatest trick that bond stress ever pulled was convincing the world it didn't exist.