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  1. #1
    Join Date
    Mar 2010
    Location
    Ocala Florida
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    92

    Default OSB roof sheathing wavy with truss lines visible

    Florida home, 15/32 OSB sheathing, no issues in attic except some minor water stains on trusses like you would see if rained on before construction or sheating install. Truss lines visible and poor workmanship on roof surface with several minor items. Any ideas on what could cause the truss lines to be so visible. I was thinking that maybe they allowed the sheathing to be rained on before shingles. Note: Lines were not visible on day of inspection, photo with visible lines is from internet. The other photos, I took. Thanks

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  2. #2
    Join Date
    Mar 2007
    Location
    Columbus GA
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    3,746

    Default Re: OSB roof sheathing wavy with truss lines visible

    The truss lines are on the roof in both photos.
    However with the sun being low on the horizon on one photo, the lines are more visible due to shadow.
    Cause: Most likely minimum construction, 1/2 OSB.
    Most likely cure: Replace/ add to roof decking

    Comments: Not likely to cause a problem (by itself) other than appearance.

    ' correct a wise man and you gain a friend... correct a fool and he'll bloody your nose'.

  3. #3
    Join Date
    Aug 2011
    Location
    Bennett (Denver metro), Colorado
    Posts
    1,394

    Default Re: OSB roof sheathing wavy with truss lines visible

    I agree with Rick. The other possibility might be that the roofing was delayed and the decking was heavily rained on for an extended period.

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  4. #4
    Join Date
    Mar 2007
    Location
    Santa Rosa, CA
    Posts
    2,481

    Default Re: OSB roof sheathing wavy with truss lines visible

    No gap/space between of OSB? This stuff will expand/contract and if the carpenters don't leave a space between each sheet, it can buckle.

    Yes, the only reason you can see it so easily in one photo is because the sun is low on the horizon.

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  5. #5
    Join Date
    Mar 2010
    Location
    Ocala Florida
    Posts
    92

    Default Re: OSB roof sheathing wavy with truss lines visible

    Quote Originally Posted by Gunnar Alquist View Post
    No gap/space between of OSB? This stuff will expand/contract and if the carpenters don't leave a space between each sheet, it can buckle.

    Yes, the only reason you can see it so easily in one photo is because the sun is low on the horizon.
    Thanks everyone, spacing was okay with H-clips.


  6. #6
    Join Date
    Feb 2009
    Location
    Southern Vancouver Island
    Posts
    4,549

    Default Re: OSB roof sheathing wavy with truss lines visible

    Quote Originally Posted by mark petty View Post
    Thanks everyone, spacing was okay with H-clips.
    In that case, the roof deck was soaking wet when they laid the shingles down, in all likelihood. Folks, it is OSB, not plywood. Learn to work with it.

    John Kogel, RHI, BC HI Lic #47455
    www.allsafehome.ca

  7. #7
    Join Date
    Apr 2011
    Location
    Bozeman, Montana
    Posts
    91

    Default Re: OSB roof sheathing wavy with truss lines visible

    Quote Originally Posted by mark petty View Post
    Thanks everyone, spacing was okay with H-clips.

    You could see from the attic that H-clips where used, so spacing on horizontal was good ( and no horizontal lines telegraphed through). But would you say spacing was adequate at butts?


  8. #8

    Default Re: OSB roof sheathing wavy with truss lines visible

    The third photo is more telling than the other two photos. From that low-resolution photo it appears that the lines trace the ends of the OSB panels - the 4 foot ends of the panels - and not particularly the truss lines. You can see the panels were installed with the recommended stagger as they were laid in successive courses up the slope. I would be suspicious that the OSB is failing on the 4-foot wide factory edge and is swelling toward the weather side, as the bottom edge is secured against the truss. I am not certain of this, but it's worth looking into. I have seen this mode of failure before, and it was confirmed by a roofer who subsequently stopped using OSB and now only uses plywood for sheathing. An added advantage to plywood, according to this roofer, is that plywood retains nails with more force than does OSB, providing better resistance to wind damage.


  9. #9
    Join Date
    Feb 2009
    Location
    Southern Vancouver Island
    Posts
    4,549

    Default Re: OSB roof sheathing wavy with truss lines visible

    Quote Originally Posted by Craig Olsson View Post
    The third photo is more telling than the other two photos. From that low-resolution photo it appears that the lines trace the ends of the OSB panels - the 4 foot ends of the panels - and not particularly the truss lines. You can see the panels were installed with the recommended stagger as they were laid in successive courses up the slope. I would be suspicious that the OSB is failing on the 4-foot wide factory edge and is swelling toward the weather side, as the bottom edge is secured against the truss. I am not certain of this, but it's worth looking into. I have seen this mode of failure before, and it was confirmed by a roofer who subsequently stopped using OSB and now only uses plywood for sheathing. An added advantage to plywood, according to this roofer, is that plywood retains nails with more force than does OSB, providing better resistance to wind damage.
    Right, as Mark said in his post, there are water stains in pic 1 that show the sheathing was rained on.

    It is possible they used an incorrect grade of OSB, we use a green edge board here for exterior, which has the end grain sealed better. There is a grade that has one sealed side kind of like a varathaned finish.

    Yes, plywood won't break away around a nail, where wet OSB will always break at the nail, impossible to pull a well nailed sheet of OSB off a building in one piece. I used an angle grinder to cut the nail heads off first, fixing my shed.

    John Kogel, RHI, BC HI Lic #47455
    www.allsafehome.ca

  10. #10
    Join Date
    Jul 2010
    Location
    Summerville, South Carolina
    Posts
    110

    Default Re: OSB roof sheathing wavy with truss lines visible

    Sometimes it happens for no discernable reason. Sometimes humps in the slab will make a truss bow up or sometimes lining the trusses up is problematical. I've seen it where you could count every sheet of osb on the roof. A thicker roofing material would help hide the framing inconsistencies though.


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