The wetness gets absorbed by the felt underlayment causing the felt to wrinkle.
Roof sheathing buckling.
The pieces of sheathing are supposed to be spaced about 1 8 inch apart so that they have room to expand and contract as the temperature changes.
Buckling can occur if the wrong type of nails were used to connect the sheathing to the rafters.
This sheathing is generally made from plywood or a similar material.
The boards dont appear to have come loose at the nails but instead have cuped badly 1 1 2 2 in places.
The nails slip out of the sheathing and create small visible bumps on the surface of your roof.
This house dates back to the 60 s with 3 4 1x8 pine decking.
Any ideas what might cause severe buckling of roof sheathing.
A broken sagging rafter will also cause a dip in the roof s surface.
Plywood and oriented strand board osb like all wood products will expand or shrink slightly with changes in moisture content.
Diagnosing other roof problems.
Under your shingles there is a layer called the roof sheathing.
Visit our blog post why is my roof sheathing sagging between the trusses.
For a good reason.
But if your roof surface is sagging between trusses lack of h clips is only one potential culprit.
This then telegraphs to the shingles above.
Plywood and osb roof sheathing are the most popular roof sheathing materials in the u s.
If the sheathing is not gapped the sheathing itself may buckle especially with thin sheathing 24 in.
For other possible causes.
But they must be installed correctly.
Improper installation of roof sheathing panels can result in warping or buckling of asphalt shingles.
Buckling shingles can sometimes be traced back to mistakes made during roof installation even though the buckling may not show up for a year or two after you get a new roof.
When plywood or osb sheathing picks up moisture it expands.
If the sheathing is properly gapped then the gaps can close causing the shingles spanning the gap to buckle.
They are easy to work with readily available and perform the job well.
Spacing and significant changes in moisture.
If the wood structural panels are tightly butted there is no room for expansion and buckling can occur.
But the moisture evaporates as the materials reach equilibrium with the the surrounding air and the shingles settle back down flat.
That can mean costly time consuming callbacks.
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The worst area is over a full bathroom that doesnt have an exhaust fan or window and theres an attic access hole directly outside the bathroom door.
