OSB and Plywood buckling roof

OSB and Plywood buckling roofs can be solved very easily.

roof-buckleHave you ever seen a roof that has had areas that were lifting up? It looks like a big air bubble that is stretching the roof sheathing, felt and shingles. Spacing of roof sheathing is very important for installers to do, as this will avoid potential for buckling.  Buckling can occur when excessive moisture is in the attic due to condensation. It can cause the OSB or Plywood to swell with the result being a buckle upward or downwards of the sheathing. Installing these sheathing panel tite without spacing can cause problems later. Some manufacturers recommend a 1/8th inch space between all panel edges to allow for expansion. One simple way to do this is adding a spacer between the panels as the panels are installed. My crews would use a nail as a spacer set in the rafters, a nail on two of the upper rafters and two nails near the upper and lower side of the panel which ever direction you are working.

apa spacing

APA recommends using a 10 penny box nail as a spacer

The American Plywood Association APA primary functions are to provide product certification and testing, applied research, and market support and development of wood products like OSB { oriented strand board } and plywood, just to mention a few. They say by “using a #10 penny box nail as a spacer is a way to gap the 1/8 inch needed for panel expansion.” Please take a minute to watch this great video where Mr. Clark of APA explains this very well. Click on the APA logo for video.

APA

Of course this is all important to do before the roof is installed. So what do you do to repair this without removing the roof?

Since the expansion of the sheathing is a result of moisture getting to the wood, then it is important that the attic be ventilated properly. The recommended amount of ventilation without a vapor barrier is 1 sq foot for 150 sq feet of attic space. This also must be a balanced system. The goal is 50% intake and 50% exhaust. When warm air from the living space meets cold air it causes condensation. By ventilating the attic, it will move the damp moldy air out of the attic. There are many ways to ventilate an attic. Seek a licensed roofing contractor to provide this service and design a balanced ventilation system for your attic to avoid future buckling of OSB.

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About author

Bob
Bob 270 posts

Since 2005 Bob has been answering questions, free of charge, here at AskARoofer.com. With a strong background in residential roofing and provides a practical and simple answers to hundreds of roof related questions, so it is easy to understand the issues you may have with your roof. Our answers are free so feel free to ask what you want. Use the green question box to contact myself or AskAroofer.com I have spent ten years as a union shingler, seventeen years as a California licensed roofing contractor with a general contractor endorsement and since Feb. of 2005 a roofing consultant. If I don't know the answer to your question, I will point you in the right direction.

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5 Comments

  1. Matt S
    March 26, 16:45 Reply
    That is a good one! Thanks for the info.
  2. Cheryl Smith
    October 22, 21:22 Reply
    My home has a problem with the plywood buckling as well. I never realized it was because there wasn't enough room for expansion. Hopefully, after we get it fixed, we won't have any more unsightly problems.
    • Bob
      October 22, 22:01 Reply
      Ventilation is very important to remove the damp air that causes the sheathing to expand but also take a look at your insulation. The heat from the living space rising upwards into the attic and mixing with the cold air Is what causes that damp air or condensation. Seek the advice of an insulation contractor for a inspection of the attic insulation.
  3. Susan Crawford
    January 08, 14:20 Reply
    This was really helpful! This was another great roofing blog!

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