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Better Wall Design?

I have a question about a wall design I haven't seen before.
What if we took 2x6 top and bottom plates with 2 - 2x4 studs 24" on center turned 90 degrees and nailed to the top edge and bottom edge. One on the outside and one on the inside with a small brace in between to stiffen the 2x4's for nailing. Kind of like a staggered stud wall, but the studs are directly opposite each other. This should provide strength and stop thermal bridging if we flash and fill the outer wall with 2 pd closed foam and fill the inner wall with R-15 fiberglass.

Then, could we put 2" of rigid foam on the outside? This would stop thermal bridging and give us a Great Wall that is good enough to reduce heating bills? A wall like this may not reach R40, but may not need to because of the closed cell foam. I'm also thinking of setting back the sill plate 2" and adding another 2" layer of ridge foam to push the R value over 40.

Framing should be fast because studs are aligned 24 " on center and two studs at 24" OC should give the strength need for the wall and increased nailing surface on both sides of the wall.

Thanks for looking at this wall design. I've never seen this design before and think it would work. Let me know what you think of this design.

Thanks for your help.

Asked by grady snapp
Posted Sat, 01/04/2014 - 12:19

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3 Answers

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1.
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This sounds like an effective idea, although I'm not sure it has particular advantages, in cost or efficiency, over other designs. If you did the standard 2x6 framing you would save lumber, and I would think the exterior rigid foam would do much to deter thermal bridging.

Answered by Howard Gentler
Posted Sat, 01/04/2014 - 15:54

2.
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i haven't had much luck with installing 2x's 'on the flat.' they are just not meant to be used that way...even with blocking

Answered by erik olofsson
Posted Sun, 01/05/2014 - 04:36

3.
Helpful? 0

Hi Grady,

I believe you are describing a double stud wall, or perhaps more accurately, a "trussed" wall.

However, I am not sure what you mean when you say "turned 90 degrees", when referring to the studs. Are you suggesting to have the "wide face" of the stud be parallel to the wall, instead of perpendicular?

If not, then I would ask you to clarify. If so, I have some concerns about your proposed wall.

Stud walls, including double stud (or truss arrangements), typically keep the studs' 1.5" face parallel to the wall direction. There are a number of reasons for this, the most important one being that studs are better able to resist wind loads along their "short face".

I would be skeptical such a wall would meet wind load requirements - but this is just my opinion - I am not an engineer.

Furthermore, as Howard Gentler points out, you are not really gaining anything. Your stud bay would be now 1.5" deep and 20.5" wide. This means off the shelf batts will need to be custom cut.

Cheers.

Answered by Jason Hyde, Peterborough/Zone 6
Posted Sun, 01/05/2014 - 08:10

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