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Small Cabin Forum / Cabin Construction / Wall shear strength
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# Posted: 6 Mar 2022 12:36 - Edited by: Aklogcabin

I'm working on plans for our new home. I'm wanting to try n achieve the best outside perimeter insulating barrier. Lots of good ideas for cabins around here.
This is what I'm thinking. 2x6 wall, spray urethane will be used between the studs. And the outside will,be 3/4" spruce boards with chinking between the boards. I am going to use 2" blueboard insulation as a thermal break. Just throwing around in my mind on how to stack the walls. Question being this.
Option 1. Starting from the inside going to the outside. Sheet rock, spray urethane, 7/16" osb, 2" blueboard, wood siding.
Option 2. Sheetrock, spray urethane between the studs, 2" blueboard, osb then the wood board siding.
Basically the orientation of the outside wall material, insulation. Should the osb be on the inside or outside of the blueboard insulation?
I do remember back in the 70s when I was working on a crew. We would lay out the walls n nail them. 3 swats for a 16d , 2 for 8d roofing n one more to make sure. Oops remembering the good ol days before nail guns. Anyways lay out walls, cut a kerf in the corners for a t strip to cover lateral forces. Stand the walls, sheet with 2" of blueboard then cover with masonite siding. Colored nails n plastic caps on your hammer so the nails stayed pretty.
This was northern WI. For wall shear strength the t straps n lateral siding provided that. On the design I'm working on I would include the t straps or use a couple l straps for compression n tension. And the use of the osb n wood board siding. Single story 28x40. We don't have a lot of wind shear and believe this would pass code.
My goal is to achieve the best insulating value for my money. Heat will be in floor radient. And a 44,000 btu fuel oil drip,stove in the living room. They look like a wood burning stove with a nice flame. And don't need electricity. We will have an 8kw generator for backup power. Lid will be insulated to r42.
Hey thanks all. I appreciate any input you all may have. Been a while since I've built a home but kinda like a bike. And there's some pretty ingenious things out now I just don't know about.

# Posted: 6 Mar 2022 14:15

After reading, and thinking through a bunch of Steve_S build details I think he has it nailed (pun intended .
I would welcome his critique, even design, if it were me building soon.

# Posted: 6 Mar 2022 15:34

Very good wall shear strength is supplied from exterior OSB sheathing when installed with the IRC recommended size nails, not overdriven below the surface and in accordance with the IRC spacing.

Better shear strength can be achieved with the same OSB panels nailed every 3 inches around the perimeter of each panel and in a staggered line along a chalk string marked line over the center of each stud. First up to 1/4" left, then up to 1/.4" to the right of the line. If the stud placement is very accurate then the factory lines may be placed exactly where the stud center is.

Back in the 70's, 80's my brothers firm also used a lot of strapping to hold walls square. He does not use them anymore at all. Simpson has three metal strapping products and while 2 of them are rated as replacements for let-in 1x4 bracing, none of them qualify for use as a structural shear panel.

What I did on my present home, was to build the wall framing with 2x4 lumber. Sheath the complete exterior with 7/16" OSB panels. (If building on a floor like most cabins here that use piers and beams, use 9 or 10 foot sheets so the panels can overlap the rim joists). The design was careful to enable the use of full size 4 ft wide panels at each corner with no cutouts. Or is a few places where that was not feasible we used Simpson Strongwall panels and or hardware kits.

Then 6 inches of Polyiso foam was added to the exterior, in three staggered layers so none of the seams aligned from one layer to the next. Wall R-value of over 40. More in the roof.

No insulation in the wall cavities at all. Attention paid to air sealing every step of the way from foam strips under the wall bottom plates, all the way through the wall.

Walls like this require a change in the way windows are installed and flashed, but is very doable.

My brother built many homes like that in the last 10 years, some with only 2 layers of foam. All have been very energy efficient.

My home uses a rain screen outer wall construction with vertical 1x strapping as an air gap spacer and then the Hardi cement fiber board over that. We get a very good wildfire rating with that.

I can heat and cool, with solar via the Mini-Split system. I do have a wood burner stove and also a propane fueled forced air furnace. The wood burner because it is a pretty red enamel thing and the standard furnace to keep the insurance company happy. At the time a mini-split was okay as heat supply but only if the home was grid connected. So I use the air ducts with the whole house heat-air ventilation exchanger. It runs on slow speed, virtually silent at timed intervals.

He also built a couple of upper class homes in the snowy cold mountains using a double wall system. Google " Riverdale net-zero house, Edmonton Alberta "

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