Ask An Expert is a question-and-answer column designed to address common questions related to forensic investigation and property damage. Each month we’ll feature one or two questions submitted by you – our readers and customers – and provide detailed, easy-to-understand answers. Email your questions to [email protected] or submit your questions here.
Question #1: If wind causes shingles to lift but does not crease or tear the shingles, will the shingles reseal? Is this considered wind damage or a pre-existing defect?
Chris Scallion, P.E., RRC: Asphalt shingles resist wind uplift by two methods. First, the shingles are nailed in place, providing a mechanical connection to the roof decking. Shingle roof systems shed water to prevent leaks, so the fasteners securing each shingle are overlapped by the next shingle course. Adhesive sealant strips provide the second method by which asphalt shingles resist wind uplift. The sealant strip is an adhesive applied to the underside of each shingle during the manufacturing process. Once the shingles are installed, radiant heat from the sun warms the shingles and bonds or seals the shingles together. A well-bonded sealant strip prevents the shingles from being lifted by wind pressure. If the sealant strip has developed full strength, the shingles cannot be separated without tearing or delaminating the shingles.
The two most common factors that cause shingles to become unsealed are a failure of the sealant strip to properly activate following installation and age-related deterioration. Factors such as prolonged storage of the shingles (warehousing), improper installation and manufacturing deficiencies can reduce the effectiveness of the sealant strip. As the shingles age, the adhesive bond of the sealant strip degrades and weakens until the shingles become loose. Shingles that are loose or unsealed could develop a weak bond following exposure to warm temperatures. Shingles that reseal in this manner are not expected to develop the full-strength bond of a sound roof system. Most unsealed shingles should not be expected to reseal, but can be hand sealed with roof cement.
Although wind may lift an unsealed shingle, wind does not cause a sound shingle roof system to become unsealed. Shingles are considered wind damaged when they are torn, creased, or detached from the roof. , Most commonly, wind damage occurs when three-tab shingles are creased by repeated lifting or flapping. Unsealed shingles without physical mat damage are not considered wind damaged.
Learn more by attending an upcoming webinar or viewing other resources at donanuniversity.com.
 T. P. Marshall, et. al., “Wind Effects on Asphalt Shingles,” 29th Conference on Hurricanes and Tropical Meteorology, Tucson, Arizona (2010).
 Stephen E. Petty, “Forensic Engineering: Damage Assessments for Residential and Commercial Structures,” 2013 CRC Press.
About the Expert
Chris Scallion joined Donan in 2012 as a forensic engineer based out of the firm’s Raleigh, North Carolina office. Mr. Scallion has worked in structural design, building envelope science and roofing. His areas of expertise include but are not limited to flood damage, construction defects and steep and low slope roof systems. Mr. Scallion’s other project capabilities include commercial and residential roofing, flood and hurricane damage, wind and tornado damage, water intrusion, crawlspace moisture, construction defects, structural and foundation failures. View Chris’s full professional profile here.