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Is sheathing supposed to overlap the corners? If not do you fill the corner with anything? If you plan to install rigid insulation over the sheathing does that change anything?

If you do overlap, how do you deal with stud spacing? Imagine you had a an 8'x8' or more realistically 24'x32' structure. What's the best way to layout sheathing to stagger seams, minimize waste and work? If you just start with a full sheet on the second side, good end with space for 1/2” sliver of sheathing.

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  • What kind of sheathing? Interior or exterior? Realistically, you end up cutting pieces off and have some leftover because you do have to offset things to fit.
    – FreeMan
    Commented Nov 15, 2021 at 19:43

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Sheathing layout is determined by stud layout (and vice versa*), and it's unlikely that a framer lays out studs with an extra ½" in mind. Sheathing usually starts at the end of a wall, or it overlaps one stud width (3½" or 5½") to cap an adjacent wall, but rarely will carpenters lap that extra half inch. There are a couple reasons for this:

  • It's better to be slightly short than too long with sheathing. Placing sheets in a production setting doesn't usually result in perfection, and you don't want a lump sticking out past the corner.
  • OSB, the most common wall sheathing in my region, is actually 7/16" thick. Do you want to deal with sixteenths now in stud layout? Nah.
  • Sheets are undersized for spacing anyway. OSB in particular calls for a ⅛" gap. You'd have to further scrutinize your calculations to deal with that or just accept that your corner will have a tiny jog.
  • There's just not a good reason to worry about it. Almost any siding system fastens further away from the corner than that half an inch, and it has no impact on energy efficiency or aesthetics.

Foam insulation should be fit more carefully for best efficiency, but it doesn't need to land on a stud at the edge so you can just shift it willy-nilly to align the corners. Also, if you're putting furring strips at the corner, over 2" foam, you're already floating in space with those--they'll need to be wide enough to reach framing. Again, that little gap in the sheathing doesn't mean much.

The bottom line is that there's nothing wrong with either way, and it has no bearing on your insulation strategy. Fussbudgets will claim that it's a matter of workmanship, but the reality is that it doesn't matter much. Plumb, level, square. Those are the keys to success with framing. Put your detail effort into the insulation and finishing.

* To find the edge of the first stud I pull from the end of the plate to 16", then back ¾" to 15¼". Each subsequent stud is back ¾" from the 16" or 24" intervals. Thus, you'd set your sheet at the end of the plate and it would fall on the center of the fourth stud (for 16" centers). Shift for wall laps as mentioned above.

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