Thread: 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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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.

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.

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.

Originally Posted by Gunnar Alquist

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.

Originally Posted by mark petty

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.

Originally Posted by mark petty

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?

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.

Originally Posted by Craig Olsson

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.

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.