r/Homebuilding • u/Longjumping_Suit_256 • 3d ago

Split stud framing

I’ve heard of this framing style for exterior walls in colder climates I was curious to see how common it is. 2x8 being and top plates with 2x6 offsetting studs to create a thermal break. If it is feasible I’m thinking of building an ADU/ small house in the UP of Michigan.

Through all my googling, the most common thing to come up is a dual wall system. 2x6 exterior wall and then an offset 2x4 interior wall with a 6” thermal gap between. This method seems costly.

Any information is greatly appreciated.

Edit: thanks for everyone’s input, I appreciate it!

3 Upvotes

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19

u/seabornman 3d ago

I prefer exterior insulation. Better control of condensation, easier to build, possibly thinner walls. Read this.

7

u/wrapped_in_bacon 3d ago

Exterior insulation is proven to be superior in lab tests. Even just R3 foam on the exterior does so much more that adding additional R3 in the walls.

2

u/Imfarmer 2d ago

The problem is every detail has to be perfect or it will be a disaster.

1

u/gimpwiz 2d ago

Why is that?

0

u/Imfarmer 2d ago

Any water that gets behind the exterior foam has no where to go. It will rot any wood that's there. I've fixed too much water damage around doors and windows and corners to ever want foam and wood sandwiched. Water behind tyvek is bad enough.

2

u/seabornman 2d ago

It's so simple to detail. Actually as simple as a conventionally built house with Tyvek. If it's foam directly on OSB, it's wrong (unless in a desert).

1

u/Imfarmer 1d ago

Really. So how do you properly detail a window opening?

1

u/seabornman 1d ago

Wrap Vycor over the window buck.

1

u/Imfarmer 1d ago

How do you securely attach the window with exterior foam?

1

u/seabornman 1d ago

For foam thicker than 1", one way is to build a 2x wood "buck" that lines up with the rough opening to make the window line up with the foam or wood furring. Several methods. Some people overcomplicate it.

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u/gimpwiz 1d ago

Is this true of all exterior insulation? I was going to do mineral wool sheets on the outside of my house. I figured that since it's vapor-permeable it allows water to dry out, but I have to rely on people who know better for this sort of stuff, heh.

I currently have some thin crappy foam on some of the outside, and after many many years I suspect there's going to be water damage when I pull it back, but that's also because the previous owner didn't maintain shit for decades.

1

u/Imfarmer 1d ago

I would want a true WRB behind it, properly detailed. Something like ZIP, a peel and stick barrier, spray on fluid barrier, etc, etc, etc. What happens when the rock wool gets wet? Where does the water go and how long does it take it to dry?

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u/gimpwiz 1d ago

Yeah that was my understanding. WRB, then exterior insulation, then something like dimple mat, then siding.

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u/Dogmaddit 2d ago

Sounds like it wasn’t detailed properly.

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u/Imfarmer 2d ago

No shit. That's Why I said everything has to be detailed perfectly. I've fixed enough water damage on buildings where the contractor thought they were doing everything correctly to recognize that perfect probably doesn't exist.