Asphalt shingles are the most used roof covering in the U.S. because of their affordability and versatility. However, there are many issues with asphalt roofing shingles that are misattributed to wind damage (Marshall, 2010). What some would call “wind damaged shingles,” are actually results of poor installation, natural aging and weathering, roofing in cold weather, contaminated glue, and expansion and contraction due to changes in climate. Read on to find what qualifies as wind damage and what doesn’t.
Wind Damage to Shingles
If you think you have a wind damaged roof, it could be helpful to know what actual wind damage to shingles look like and how it happens. For a shingle to be wind damaged, an uplift force from the wind has to occur. This causes a pressure dissimilar between the front and back faces of the shingle. The more the shingle lifts off the roof, the more surface area is exposed between the shingle and the roof, leading to a greater uplift force and faster degradation.
As wind blows, it will cause inward and outward pressures on the walls and roof of a building. Any force, including wind, will seek the path of least resistance. This means that when wind hits the side of a house it will move up and over the roof to continue flowing. As it passes the ledge it will create a suction force on the face of the roof, similar to what occurs with an aircraft wing. This is understandable since an aircraft is able to fly due to this uplift force; granted, with a smooth metal wing. On a roof, textured shingles begin to lift because of this turbulence and can cause issues over time. If any problems of faulty manufacturing, climate, or installation occur, this is especially true.
A Note to Contractors
The highest uplift pressures on a roof are in areas of change, such as along corners, eaves, ridges, and rakes (Marshall, 2010). This means that it is particularly important to add additional anchoring in the areas of the most uplift.
Climate Effects on Shingles
We can’t blame all roofing repair on the wind: some problems stem from environmental temperatures. When shingles start lifting in a uniform, diagonal stairway pattern, they are known as “racked.” When they lift in a straight-up line like a zipper, it is known as “zippering” (go figure!). These are usually a result of climatic expanding and contracting. This is self-evident, since wind blows in all directions, and wouldn’t lift shingles in a uniform fashion. In this case, the line where they lift typically follows the way the contractor installed them. If new roof installation happens in extreme conditions of cold or heat it won’t last as long either.
Other uniform roof anomalies include cupping and clawing, where shingles curl up around all edges of the tab (cupping), or suction downward on all edges (clawing). These most likely have to do with the uneven absorption of water and not with the wind.
Natural Wear On Shingles: How Long Does a Roof Last?
One study by the University of Florida revealed that lifted shingles were more likely due to “a systematic failure of the shingle’s sealant strip” than some other external factor (Dixon, 2013). This is because the sealant strip naturally loses adhesion over time. This natural occurrence leaves the shingle partially unsealed and susceptible to the uplift force of wind and rain. Dixon et al. (2014) observed that asphalt shingles typically stay sealed for 4 to 5 years, and then begin to naturally deteriorate. The average manufacturer’s estimate for an asphalt shingle roof lifespan is about 20 years. This number obviously fluctuates depending on location and weather conditions.
Faulty installation & Human Error
The study by Dixon et al. (2014) also found that unsealed shingles can occur from poor installation. 70% of roofs studied showed errors including debris in the sealant strip, under-driven nails, and release tape that was accidentally stuck to the sealant strip from packaging mistakes. These roofs all had a distinct pattern in their damage, meaning they didn’t result from wind (Dixon, 2013). Sealant for roofing needs to be handled properly to ensure an optimal seal when installing shingles. Contamination to a shingle’s sealant strip can also happen in industrial areas where exhaust or chemical residues are abundant. This can affect a roof even more than weather conditions (2014).
If you’re trying to verify your roofing warranty, it is important to know whether the weather, contractors, or manufacturing are the culprit behind your roofing damage. Don’t let lack of knowledge keep you from having a reliable, economical, and overall good roof!
Craig R. Dixon. “The Influence of Unsealing on the Wind Resistance of Asphalt Shingles.” Journal of Wind Engineering and Industrial Aerodynamics. Vol. 130. Elsevier. 2014. pp. 30-40.
“Procedure for an Evaluation of Wind Damage to Shingles.” Prugar Consulting, Inc. Accessed October 11, 2018. http://prugarinc.com/shingles/procedure-for-an-evaluation-of-wind-damage-to-shingles/.
RCI. “Misconceptions of Wind Damage to Asphalt Composition Shingles.” RCI, Inc. June 07, 2018. Accessed October 09, 2018. http://rci-online.org/misconceptions-wind-damage-asphalt-composition-shingles/.
T.P. Marshall, S. Morrison, R. Herzog, and J. Green. “Wind Effects on Asphalt Shingles.” 29th Conference on Hurricanes and Tropical Meteorology. American Meteorological Society. 2010. Hyannis, MA. p. 11.
“What Roof Lasts the Longest?” What Roof Lasts the Longest? – Roofing Southwest. Accessed October 12, 2018. http://www.roofingsouthwest.com/blog/what-roof-lasts-the-longest.