headers in gable end walls? what do you engineers think?

i am framing a superinsulated house in northern minnesota (40 psf snow load). the specs call for no headers in non-load bearing exterior walls (gable walls). i'm not entirely trusting this architect--he's no structural whiz. my question--is a wall supporting the rake overhang really non structural? it's a two story house on a walkout basement. it has 24" overhangs, framed with lookouts which bear on a drop chord gable truss which sits on the so called non-bearing wall. what do you guys think about no headers in such a wall? the headers are left out to reduce thermal bridging.
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Sounds good to me. The gable end isn't holding up much, if any, of the roof. The trusses are supporting the overhang. Some inspectors in my area want to see a header over every opening in the wall.
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marson wrote:

First, I live in South Florida and snow load is not a issue but rather designs are based on high wind designs. As a result, most building dept. down here reject framing plans that call for gable end trusses. Secondly, the end wall on gable structure are structional load carrying walls! Just look at your truss engineering for the drop gable end truss. The truss engineering will show the PLF for the bottom chord for continues bottom chord bearing. Granted, the gravity loads will be much lower than the in-field trusses since the in-field trusses will have two points of bearing while the gable end will have continues bearing on the top plate of the gable wall.
Consider ballom framing the gable end wall and eliminate the gable trusses.
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tj wrote:

so explain the advantage of balloon framing a gable wall in my case? we don't have wind loads to speak of. and even if you have to add t bracing, you're way ahead on labor with a truss.
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In a previous post marson wrote...

You need some sort of structural member (header) to transfer wind loads horizontally to the sides of the opening. This is especially true if the opening is very large (let us say over 3 feet).
Here in the Pacific NW it is common to install headers in gable end walls, but they are often 4x members in a 2x6 wall. 2" of rigid insulation is glued to the inside face and GWB is applied over with longer screws.
--
Bob Morrison, PE, SE
R L Morrison Engineering Co
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Thanks for the reply. What do you mean exactly by structural member? I was planning to use two two by fours oriented "flatwise" in lieu of a insulated tji header. And if lateral loads are the issue, then I'm thinking I don't need to worry about the walkout walls where the floor plywood above is tied to the foundation.
Bob Morrison wrote:

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In a previous post marson wrote...

(2) 2x4 flatwise perform OK for horizontal loads as a structural member. I sometimes specify 4x6 flat for small openings to get better vertical performance as well.
You could also form an "L" with (2) 2x and get reasonable performance over small (3-foot) openings.
--
Bob Morrison, PE, SE
R L Morrison Engineering Co
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I live in the Pacific NW too, and I used two 2x10 headers over every door and window opening (2x6 walls), even on the gable ends. One aligned with the exterior, one aligned with the interior, and then filled the 2-1/2" space in between with insulation. I added a strip of 1/2" plywood along the bottom edge to provide a continuous surface for installing the window and trim. This offered better insulation than a solid or built-up beam, eliminated the need for cripple studs over the openings, and provided plenty of support for each opening. It also gave me plenty of nailing area for the exterior sheathing and interior wall coverings. Several of the headers were cut-offs from longer floor joists, so there was also very little additional cost.
Question for you Bob... If insulation were a big concern, could you rip 2x6's down to 4-1/2" then build a box beam with a layer of 1/2" plywood on each side, filling the center with rigid insulation? Especially for a gable end, it seems like it would offer plenty of support for the average window opening.
Anthony
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That's the way I like to build headers also. In 2x4 construction I use a piece of 1/2" Tuff-R between the wood to pick up an extra R 3 on each header.
-- Dennis
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In a previous post HerHusband wrote...

Seems like a lot of work. That's why I typically go for 4x headers with 2" rigid glued on the inside face. This offers plenty of support for GWB if you use long screws. This will require longer finish nails if you are trimming out the opening in wood, but most of these houses use GWB for the top and sides of the opening and only have wood on the sills, where of course you have a 2x6.
BTW, I agree with you idea of using a taller header in order to eliminated short blocks between the header and the double top plate. The wall frames faster that way.
--
Bob Morrison, PE, SE
R L Morrison Engineering Co
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Of course the whole reason for eliminating headers in gable walls is to reduce thermal bridging. Wood is about R 1 per inch, so less wood and more insulation is the goal.
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marson wrote:

You originally said that you are framing a "superinsulated house" in northern Minnesota, yet I get the impression your wall frame is just 2x6 studs with some reduction in thermal bridging in plates, headers, etc. I am curious as to what your whole wall looks like and what insulation you will be putting in the cavity, plus what total wall R value you are shooting for. If you have 2x6s 16" oc, that's a lot of thermal bridging.
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Dick Russell wrote:

For the most part, it is a 9" double 2x4 wall with dense pack cellulose. The outer wall is the load bearing wall. We are shooting for R-36. This was not my idea, and I would have steered the client toward a 2x6 wall, spray foam, and 1" foam on the outside to address thermal bridging, but I got the project too late in the process to give my two cents worth. Eliminating headers in the gable end walls was a spec I was given on the plans. The architect specializes in energy efficient houses. (in reality, I realize that "thermal bridging" isn't exactly the issue with headers in this case--we want to eliminate unnecessary wood where possible.) I posted the question because the I don't necessarily trust the architects structural judgement--after all, noone will call HIM if the sheetrock cracks!
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Agreed, but if you were trying to pack as much insulation as possible in a 2x6 wall header, it seemed like a possible option. Of course, you'd still have the thermal bridging of the studs themselves, but that's a different case... :)

Is there some reason you don't use separate 2x material on each face and put the insulation in between? You don't need longer screws for the drywall, and it offers better support for things like curtain rods.
I suppose it offers slightly less resistance to horizontal wind loads, but I would think the double 2x6 top plate would take care of that?
Anthony
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HerHusband wrote:

well, where we do need a header, we use pre insulated tji headers (http://www.swi-joist.com/p_04.htm ). might not be available in your area. but 4x material is not stocked in yards where I live.
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