I am wondering if there is a general consensus regarding applying the lateral stability factor for wood headers in a wood stud wall.

opinion 1. Assume = 1 because the ends are rotationally restrained and the stud wall above the header provides lateral restraint.

opinion 2. Calculate specific value <= 1.0 based on ends rotationally restrained but header not laterally restrained.
  a. Loading assumed uniform for most cases
  b. In some cases, concentrated load due to girder truss etc.

I am leaning toward opinion 2 because typical header is at least 2' below "true" lateral restraint provided by floor or roof structure.

 

I assume that headers are unbraced for out their entire length. The header braces the cripple studs, not the other way in my opinion.  

Now if your header is tight to the bottom of your top plates or replaces the top plates and is at least toe nailed at some regular interval to the top plates above or perp joists then yes I'd say that you could conser it braced.  

Per the NDS section 4.4.1 as an alternate to CsubL 1) d/b equal or less than 2 (4x8 or smaller) no lateral support is required. 2) d/b greater than 2 and less than or equal to 4 (4x10 to 4x16) the ends shall be be in position.
So for 4x headers greater than 4x8 it depends on the end connections.

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.

Garth,

The usual headers are 2 - 2 x 6 to 2 - 2 x 12. Less frequent are triple 2 x's in some cases where the wall studs are 2 x 6.

Garage door headers (16' door) are 2 - 2 x 12, 3.125 x 10.5 GLB to 3.125 x 16.5 GLB in most cases.

4 to 8 - 16d nailed thru the first king stud into the end grain of the header. That's the rotational restraint.

Is that adequate for end connection in the NDS? Seems so to me.

That NDS info is useful. Never was aware of it.

I ran some examples on my Excel workbook:

2 - 2 x 6, span = 8'   CsubL = 0.99
2 - 2 x 12, span = 14'  CsubL = 0.94
3.125 x 12 GLB, span = 16'  CsubL = 0.75
3.125 x 16.5 GLB, span = 16'  CsubL = 0.56

The volume factor for both GLB examples was 1.00 so the CsubL governed.

I would not recommend the use of end nails for rotational restraint. I prefer to use Simpson LTP4 each face of beam to king stud when needed.

Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.