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Must one frame exterior walls with 2x6 and not 2x4 to satisfy IRC2018 and IEC2018?

W

Willin

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Gulf
A small addition to a 100 year old seasonal "camp" is wanted to be framed in 2x4 so window and door details exactly match what is seen in existing. We can meet all structural needs with the 2x4 walls, and pass ResCheck by using sprayfoam in wall cavities, and one of the Huber ZipR sheathings.

I cannot find a hook in the codes which would mandate 2x6 framing and not permit 2x4 framing. Is there such language?
 
Don't have to. The IRC2018 is the code aside from energy, which is IEC2018, and I can find nothing in either mandating 2x6 exterior wall framing. Can you?
 
The code does not explicitly address every combination of circumstances. I know that we would use 6" studs to accommodate mat insulation but there are other ways to insulate.

Comply with the provisions in the building code that you know about. My perception is that if you provide sufficient insulation the code does not care how thick the wall is.

Submit it to the building department for permit. If they disagree then they will tell you what provision you have violated.

I suspect that an Mechanical engineer who designs HVAC systems will be most knowledgeable and should be consulted if it is important to you.
 
Willin said:
Don't have to. The IRC2018 is the code aside from energy, which is IEC2018, and I can find nothing in either mandating 2x6 exterior wall framing. Can you?
Click to expand...
I am still not understanding a few things.

First, what is a camp? If this is a seasonal, traditional "camp" then I don't see how the IRC applies at all.

Second, if you are stating that you cannot meet the energy code and structural needs with 2x4 then why would you need a code to state that you have to use 2x6? By default if 2x4 construction is not adequate and 2x6 is then I don't understand the need for verbiage in the code.
 
If you can meet structural and energy, you can use 2x4....For that matter, you can use laminated chicken fat, but you will need an engineer for that....
 
Conventionally, 2x6 walls are only necessary for meeting the energy code. If you can meet the energy code via spray in foam and insulated sheathing, you should be good to go.
 
The 2018 energy code may (depending on climate zone) "prescribe" an R-20 wall. I does not "mandate" any level of insulation for walls if one chooses to use one of the performance based compliance methods. The UA Alternative allows you to trade-off one area for another. Maybe you do R-13 walls but have R-10 windows and R-100 attic or something. There is also the Building Performance Alternative and the Energy Rating Index Alternative.
 
$ ~ $ ~ $

** steveray **, ..."Laminated chicken fat" ?........Is there an ES Valuation report on
that ? :p

$ ~ $ ~ $
 
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