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So I am working out a framing plan for an exterior wall made from 2x8s and I want to put a door in it. I plan on using two 2x12s for the header.

The question is, what is the best practice for building the 2x12 header in this deep of a wall?

The width of the header would ideally be 7 1/4" so that the cripple studs above the header are flush with both sides of the header. But that means filling in with 4 1/4" of material, which seems strange.

Do I just make a box out of 2x12s (two the length of the header, plus two at 4 1/4" making the short end of the box)?

Edit: And perhaps would it be best practice to add one 4 1/4" 'header spacer' in the box under each cripple?

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since I have no idea why 2x8 framing is being used, i wont bother trying to comment on the design requirements. if its just for insulation, go 2x6 an solid polystyrene foam for insulation. your r -value will be higher than fiberglass in a 2x8 wall.

however, a header that big would be abnormal, not from the height issue, but the depth of the wall. how wide the span is going to dictate the construction. you can do it three ways:

1) (short span) - inside and outside 2x12 on edge, fill with width ripped 2x6 short studs with a ripped 2x6 plate top and bottom between the header members

2) (middle span) - box beam construction. top and bottom plate of 2x8, inside and outside 2x12 on edge. nail together like nails are free. tall assembly, but that's the strongest with minimal material. you can block internally if you want, but it won't make much difference

3) (longest span) multiple 2x12 on edge with plywood filler at center to make with correct

4) (strongest) - LVL instead of spruce. built like 1), but 3 to four times stronger

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  • My application only requires 2x10 for the header but I will have excess 2x12s so I am beefing it up beyond minimal spec. I like your middle span solution the best and have a ton of extra room above the door. Perfect, thanks!
    – alfreema
    Commented Dec 2, 2015 at 4:26
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I am not familiar with 2x8 framing construction (is that even a thing?) but you might look into the way 2x6 construction @ 24" o.c. (a.k.a. "advanced framing") is done. Advanced framing is laid out a little differently than standard 2x4 framing, including different headers, single top plates, no cripple studs, among other differences.

I guess it partly depends on why you are doing 2x8... is this for load-bearing purposes? In which case you really should have an engineer design this highly unusual wall. Or is it just so you can fit more insulation in the cavity, in which case I would think you could just follow a 2x6 framing plan but use 2x8s instead. In any case, double 2x12s seems like a very serious header.

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  • It is indeed very unusual. I can make 2x6 work (I have worked with advanced framing, and actually like both it and old school framing depending on the circumstance). This wall is filling in an old block wall with large airplane hanger sliding doors and the 2x8 wall just works perfectly in this case.
    – alfreema
    Commented Dec 2, 2015 at 3:50
  • Ah just went and reviewed the advanced framing headers. Those panel box headers seem so chintzy, but great from an insulating standpoint. My layout will be reviewed and ultimately stamped by a structural engineer but I wondered what a best practice in this situation is. I better hit the header span tables again though, this span is longer than I originally remembered.
    – alfreema
    Commented Dec 2, 2015 at 4:02

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