2x8 header vs 2x12

[OlJarhead]

My question is this:

Why use a single 2x12 header on load bearing walls with spans of 4 feet or less (14x24 builders) rather then doubled up 2x8's?

I'm just curious becuase I was thinking 2x8's leave more room between the header and the loft plate on a 10' wall that you're installing the loft plate at 7'6".

Also, when using one 2x12 header I'm assuming you need to box it in top and bottom?  So one 2x6 flat on the top, the 2x12 on edge and then another 2x6 flat under it.

Also, does the single header go to the outside of the wall to allow insulation to the inside?

Thanks!

[John Raabe]

A single header is normally done for more complete insulation. It can be placed on either side of the framing. It can be notched into the stud on either side eliminating the cripple (advance framing technique). It can be extended a bit and put on the inside of the wall to provide anchorage for window coverings. Yes, you might want to use double headers when you want to set the window higher. You can use a 1x to box in the top of the framed opening if it will provide enough of a nailer. It can be cut down and nailed through the bottom of the header rather than extending down below it.


From Superinsulated Design and Construction.

[Don_P]

The header could be the same piece of wood as the loft support ribbon if elevations, opening spans, and loads allow it to work out.
I was curious and checked the section modulus of a 2x12...31.64 vs a double 2x8...26.28. A single 2x12 is a stronger beam than a double 2x8, or as the old adage goes "Deeper is cheaper".

[OlJarhead]

Thanks!

I stuck with the 2x12 as I realized what you posted here -- more insulation! and probably cheaper.  And since my walls are taller not an issue for the windows!

Thanks!!!