Roof Shingle - Aging of Shingles

Aging of Shingles

Left: Example of faster asphalt shingle wear along eaves due to channeled water running down the roof. Right: Severe shrinkage resulting in tearing away of entire tabs. Note the exposed nail heads. Water running down the roof can seep around the nails into the interior space.

The protective nature of paper and fiberglass asphalt shingles primarily comes from the long-chain petroleum hydrocarbons, while wood shingles are protected by natural oils in the cellulose structure. Over time in the hot sun, these oils soften and when rain falls the oils are gradually washed out of the shingles. During rain, more water is channeled along eaves and complex rooflines, and these are subsequently more prone to erosion than other areas.

Eventually the loss of the oils causes asphalt shingle fibers to shrink and wood shingles to rot, exposing the nail heads under the shingles. Once the nail heads are exposed, water running down the roof can seep into the building around the nail shank, resulting in rotting of underlying roof building materials and causing moisture damage to ceilings and paint inside.