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bubble or bow in osb shealthing

DoRight's picture

I recently installed about 40 sheets of 4 x 8 siding over osb shealthing.  Teh house had been sheathed over a year ago, covered with  paper and left to stand.

After installing 35 or so of teh 40 sheets I ran into a weird situation.  I found two ... for the lack of another word   ... bubbles in the OSB.  Two bubbles, bowing out atleast 1/4 of an inch, maybe 3/8.  They were about 2 feet long (up and down) and most of the width of teh stud bay.  the osb was nailed nicely to teh studs on each side of the bubble.

Has anyone seen this before? And what do people think the cause is? Defect in the osb? I would think maybe the wall had some excess strain or load, deforming teh framing, causing the obs to buckle, but I just don't see where such strain would come from and I would think such a stain would casue a twisting over the entire sheet and not oval shaped bubles.


As it was I slit teh bubbles, installed some blocking behind it and nialed the obs to teh blocking to flatten the wall out.  weird.



No one? (post #214018, reply #1 of 9)

Nobody has seen anything like this?  BUMP


The probable cause of the (post #214018, reply #2 of 9)

The probable cause of the "bubbles" (buckling) is the lack of expansion joints between butt joints in the sheathing. I am assuming you used OSB/plywood support clips between rafters or trusses. These would provide the expansion joints needed across the 8' length of the OSB sheets. Asphalt saturated roofing paper is not meant to be left exposed for a year. You should have used a (much more ex$pen$ive) roof membrane for that purpose.  Moisture and the lack of expansion joints are the most likely causes for buckling. I hope you spaced your sheathing nails in accordance with OSB specs.  Cut out the offending (buckling) sections of OSB. Don't try to fix them the way you have described!!!  Sorry to be so blunt.



Mel Fros

Wall (post #214018, reply #3 of 9)

It's a wall.

its a wall (post #214018, reply #5 of 9)

Yes it is a wall.  I do not know very many people installing 40 sheets of siding on their roof as my first sentence mentions.  Not to be blunt.


Still might be caused by too little expansion joints (post #214018, reply #6 of 9)

Still could be inadequate sheet spacing. 

Like I said in the entire house I found it in two stud bays.  I suppose it could be elsewhere, but of miniimal distortion.


I've seen it but no idea what (post #214018, reply #4 of 9)

I've seen it but no idea what causes it. We ran the saw through the middle and screwed it down. Worked fine.

Florida Licensed Building Contractor, 50 years experience in commercial remodeling, new homes, home remodeling and repairs and all types building maintenance.'s a wall. Assuming (post #214018, reply #7 of 9)'s a wall. Assuming the wall is properly supported (foundation wall...footing etc) I still believe the cause for buckling is the lack of expansion joints. There is no point in trying to nail down the buckled areas if there are no expansion joints. My recommendation: deal with expansion joints first (both vertical and horizontal). Don't just re-do the trouble spots; cut X-joints everywhere. Then undertake replacement/repair work.

Mel Fros

Absolutely right on the expansion (post #214018, reply #9 of 9)

You are spot on about expansion. If you read my following post, you will see how it is easily fixed, ( if you catch it early) If you wait to long, your sheet goods may stay disformed,bowed, and buckled. This is a major problem if your dealing with a roof system or wall system that has been covered with finished material. After a certain point, no sheet goods will lay flat, even given proper expansion joints. They have already been trained into their existing state. 

expansion joints (post #214018, reply #8 of 9)

I experienced a similar problem, many years ago when OSB was a brand new product. It was so new, in fact, I called the lumber company rep and asked him if I had to provide expansion joints (as with regular sheet goods), and I was told no. It is stable and not too. We sheathed the inside of a very small warehouse (walls) in it, butted it up tight and  were going to batten it the next day. I got a phone call from the owner, the next morning, telling me that I was going to have to replace all the osb because his walls looked like a snake. I told him that I had a solution and I'd be there soon. I told him that the (blandex) had expanded and was pushing against itself and that I had a solution. He jokingly remarked,"So it's growing?, Next thing I know, I'll have little baby blandex's running around the floor!) We got there and had to cut an expansion groove in every joint but you could see it relax and straighten out almost immediately. That's the last time I listened to a lumber rep.