# 2 questions about installing OSB exterior sheathing



## hotrodjohn71 (Jan 23, 2017)

I am hoping this is the correct area for this question. If not, please advise and I will repost.
2 questions about OSB exterior sheathing.
First is the corners. Please.see the pictures as I see it done 2 ways. One is to bring the corner edges of each sheet together at the corner totally hiding the corner stud. The other way, they stopped at the corner stud edge and did not make a connection of the OSB at the corner. Which way would be correct.
Second question. Researching I have found some like to apply the sheathing horizontally, and some say all vertically is better because that way, attaching at the studs creates a total gap-less application preventing wind entry into the wall and making a good seal. The ones who are in favor of the horizontally application say that's better because the sheathing needs to let the inner wall breathe and if you are going to go 'all vertical' that you should actually cut some slips in the sheathing to allow ventilation. Which is correct.
Thanks.


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## jlhaslip (Dec 31, 2009)

Usually install the sheathing so the corner is hollow and not overlapped to keep the corner from interfering with the siding corners, depending on what that might be. 

Code here is to leave a small gap between horizontal sheathing to allow the wall to breath outward. Use the thickness of a 2 1/2 inch nail as a spacer. About an eighth of an inch.


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## carpdad (Oct 11, 2010)

Sheathing corner overlap doesn't matter. Usually it is determined by the layout because the carpenter might take the overlap into the numbers. The image you show may not always work. Search for corner stud build that has the most area for nailing. That image does not have a wide nailer. Vinyl is fine with nailing into the sheathing.
Horizontal, I think, is better because it is more bracing area across more studs. You can use clips for better fits and spacing. OSB needs expansion spacing.


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## hotrodjohn71 (Jan 23, 2017)

Thank you.
Do you recommend blocking between the studs at the horizontal edges of the sheathing where one meets the one above it?


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## jlhaslip (Dec 31, 2009)

hotrodjohn71 said:


> Thank you.
> Do you recommend blocking between the studs at the horizontal edges of the sheathing where one meets the one above it?


No. See my comment above re: allowing the inner space to breath to the outside.
The wall sheathing needs to be selected for your stud spacing. Wider spacing needs thicker material. 3/8 works for 16 c/c studs.


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## CrazyGuy (Nov 18, 2017)

I, as well as every home builder I ever worked around, would not attempt to leave air gaps in a wall. The wall will breathe without leaving gaps in it with wind blowing through the place. 

The top picture is how you should do your corners. You should put the OSB on vertically, unless you want to cut and install nailers for the seams. You do not want loose seams on the OSB, you want it to be secured to framing in a solid fashion. And unless you are building a cardboard box, I would go with at least 7/16. 

Make things tight & solid with nothing floating around unsecured. Add house wrap as well when done.


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## jlhaslip (Dec 31, 2009)

CrazyGuy said:


> I, as well as every home builder I ever worked around, would not attempt to leave air gaps in a wall. The wall will breathe without leaving gaps in it with wind blowing through the place.
> 
> The top picture is how you should do your corners. You should put the OSB on vertically, unless you want to cut and install nailers for the seams. You do not want loose seams on the OSB, you want it to be secured to framing in a solid fashion. And unless you are building a cardboard box, I would go with at least 7/16.
> 
> Make things tight & solid with nothing floating around unsecured. Add house wrap as well when done.


Building code for this cold climate requires the gaps. 
Sorry, I disagree with backing at the seams even without the gap. Proper selection of sheathing is the important part. Only time I have backed the seams was with an unheated storage shed where security was an issue.


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## CrazyGuy (Nov 18, 2017)

Sure isn't code here and it's cold. Did you ever see what happens to OSB when it catches a little moisture, heat or temp swings that isn't secured to a solid board? Warps like heck. That would be real nice to have that happen inside a wall, bubbles pushing out siding in spots, plus, your apt to break an edge when pounding a nail into it.

In addition, I can't imagine the amount of heat loss by intentionally installing gaps in a wall. You lose enough heat when building it tight.


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## CrazyGuy (Nov 18, 2017)

I just went and did a little studying on this and I now see where you guys are coming from, I never knew the problem existed, but it seems to be very rare. Maybe weather related issues or manufacturer issues do play a big part. Even with knowing about this rare issue, I will continue to butt osb tight with solid backing. I don't like the idea of sheets just floating even with clips, solid wood backing is my only way. I like things stout. It's always worked around here, but I will give you, maybe it doesn't everywhere. Learned something new, thank you.


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## carpdad (Oct 11, 2010)

BTW, the stud arrangement in the image shows you can't insulate the space from inside. Also air block. There are other ways to save on the material or insulation value. I think there are images of other ways. Depends on your budget and what you want, but you don't save a lot by adding extra insulation or following new framing technics.
No blocks for sheathing joints, usually. 1/2" nominal sheathing can span 16". OSB may deform more than regular ply, so clips are usually used for roof or wider spans because the scallops (name?) shows through the shingles. Don't know now, but clips were mandatory for osb.


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## jlhaslip (Dec 31, 2009)

CrazyGuy said:


> I just went and did a little studying on this and I now see where you guys are coming from, I never knew the problem existed, but it seems to be very rare. Maybe weather related issues or manufacturer issues do play a big part. Even with knowing about this rare issue, I will continue to butt osb tight with solid backing. I don't like the idea of sheets just floating even with clips, solid wood backing is my only way. I like things stout. It's always worked around here, but I will give you, maybe it doesn't everywhere. Learned something new, thank you.


I think it started on the rainy West Coast and their leaky condo situation a few years back. Google that to see a real kerflufle.

The Lower mainland also stipulates use of a rain shield on top of the tyvek under vinyl siding. That creates a drain plane for water to escape. The OSB spacing allows water vapour to escape into the drain plane.


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## chandler48 (Jun 5, 2017)

We have begun to use Zip panels and only install them vertically on walls, taping the seams. Then WRB (Tyvek), window/door tape. Of course we don't have the weather you guys have, and we don't know where the OP is located.


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