2 X 6 wall with 2 X 4 staggered studs
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We are in climate zone 5a. Our CGL Policy prohibits the use of exterior rigid foam over frame construction. Our last home was built with 2×6 at 24” on center. We used Cellulose with OSB and House wrap with Cement Plank siding. I would like to use a 2 x6 top plate and stagger 2 x 4 studs 12” on center to reduce thermal bridging. Any thoughts?
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Replies
Steve,
What is a "CGL policy"?
Some thoughts:
1. People have built houses using the technique you describe.
2. It's barely worth the trouble to build a double-stud wall on 2x6 plates. Any chance you can change your plates to 2x8s or 2x10s? The wider the plate, the better the performance. It takes just as much labor and almost exactly as much material to build a double-stud wall on 2x6 plates as on 2x10 plates.
Is there a reason you would need to go to 12" on center studs with this type of wall system?
Curtis,
I think Steve means that he would be building two 2x4 walls. Each wall would have studs 24 in. on center. Since there are two walls, and the studs are staggered, you end up with one stud every 12 inches.
As Martin said, if you are going to go through the trouble of a double stud wall/staggered stud wall might as well make it thicker so you can add more insulation - that is where the benefit comes in. The reduced thermal bridging could potentially be offset by the additional lumber in your wall. A 2x6 wall @ 24" OC will have more insulation and less lumber than a staggered 2x4 wall @ 12" OC as you suggested.
Is the CGL your commercial general liability policy? I have never heard of an insurance policy limiting the materials to be used by a construction company.
I'm not surprised by the OP's policy restriction on foam outsulation. The company correctly recognizes that a lot of builders are going to blow it with this detail and have mold/moisture claims against them. My policy has quite a few exclusions, including a couple of specific materials/systems like EIFS.
Agree with others that the wall should be thicker. Staggered studs on 2x6 plates hardly seems worth it.
Steve: And why not two separate 2x4 walls? 2x10 plates get spendy; faster, perhaps, but spendy. That way you break up the wood bridging, too. Look at prices of wood and labor. I can buy 2, 2x4s for less than 1, 2x6. Labor may run the bill up, though.
CGL is commercial general liability policy they are treating it as a EIFS system. It is in most CGL policies that I have looked at along with a new rider that prohibits the use of Chinese Drywall. The 2x6 makes sense in that windows, doors and trim work out. The cost is not much more. I do like the idea of a double wall construction, but the cost may be prohibitive. Until we can get value form appraisers and realtors we need to be cautious. It does not matter how well we build if we cannot sell it.
If you can't build an 8" thick wall its a lot easier to build one 2x4 wall and put 2x2 horizontal strapping horizontally on the inside, talk to your electrician and drywaller first though.