Reading Your Own Roof
Lesson 10. What Wind Damage Looks Like
At a Glance
- Shingles seal themselves down with a tar strip
- Wind breaks the seal, then the shingle lies back down
- The damage is invisible until the next storm takes it
- Look for lifted corners and a shiny line under the tab
The Seal Strip
Every asphalt shingle has a strip of adhesive across its face. When the sun warms a new roof, that strip softens and glues each shingle to the one below it. That bond is what holds a roof down in wind, far more than the nails do.
Wind lifts the bottom edge of a shingle and pulls that bond apart. Then the wind drops and the shingle lies back down, looking exactly as it did before. It is now loose, and the next ordinary storm takes it off entirely.
How to See It
- Corners of shingles sitting slightly proud of the ones around them
- A shiny or dull line across a shingle where the seal has torn
- Shingles that move in a light breeze when nothing else does
- Creased shingles, with a horizontal fold line, which are broken even if attached
- Debris in the yard, in the gutters or in a neighbor's yard
Straight Line Wind in This Valley
The Midwest gets far more straight line wind damage than tornado damage. A derecho can push severe straight line winds across hundreds of miles, and eastern Iowa knows what that looks like.
Wind damage is usually concentrated on one or two slopes, the ones facing the storm, and on the edges and ridge where wind gets underneath first. If one side of your roof looks different from the others after a storm, that is the tell.