When in doubt use 2 by 12 inch headers.
Non load bearing garage door header.
Most door frames that are 4 feet wide or less require a 2 by 6 header.
The load that you need to resist is the horizontal force on the wall above the new door.
When framing in 16 centers a good rule of thumb when figuring material is one wall stud per foot of bottom plate.
Section r502 5shares allowable girder and header spans.
A header is to hold something up.
A header needs a full or king wall stud on each side of the opening extending from the bottom wall plate to.
I d use a double 2x6 laid flat at the head of the opening.
Framing for a non load bearing door header measure the door.
If your walls are non load bearing a single top plate is all that is required.
For instance in the basement remodel all the doors have simple 2 4 framing around them.
On previous projects i have been supplied a glu lam boise makes specifically for garage door headers that was 3 1 2 x 11 1 4 x 18 9.
This is non bearing so you could use studs to create the space down from the roof or ceiling for the roll up door to roll up into.
If they are load bearing a double top plate is required.
Pro tip you can access a free copy of the 2012 international building code here.
Measure the width of your door frame.
Non load bearing windows and doors do not require a structural header.
Between 4 and 5 feet the header should be built 2 inches wide and 8 inches long while a larger opening needs a header that is 2 by 12.
This will usually give you the extra studs needs for corners and door openings.