Even low wind speeds during a typical thunderstorm can damage shingle roofs, which can see escalating effects as wind speed increases, according to the National Weather Service. The severity of wind impact depends on more than just wind speed, however, and other causes of loss sometimes mimic the effects of wind on shingles. Identifying key characteristics of wind and other perils, as well as the factors that contribute to each, ensures a more accurate diagnosis of the cause of loss.
Strong winds may entirely dislodge shingles, but there are less obvious indicators of wind damage.
What Is Wind Damage?
It’s worth noting that some shingles may be affected by wind without losing functionality. Shingles’ main purpose is to shed water and prevent it from damaging the roof structure; unless their ability to do this is compromised, they won’t be considered damaged.
Shingles that are creased, dislodged, or removed may be indicators of wind damage. Wind may cause unsealed shingles to flutter but leave them in place. It’s important to consider all the factors before making a hasty diagnosis.
In addition to wind speed and direction, the orientation of the shingles plays a part in the severity of the damage to a roof. Shingles on the windward side of the roof and those along the hips, ridges, and eaves are more vulnerable.
Wind pressure is greatest at the edges of a roof, and shingles commonly become unsealed as they age.
Installation and attachment methods also contribute to the vulnerability of shingles. Missing or misdriven nails, or shingles installed using inadvisable methods all increase the likelihood of wind damage.
Certain types of shingles are more wind resistant than others. Dimensional shingles, which are stiffer than three-tab shingles due to their laminated extra layer, are less likely to be damaged by wind. Dimensional shingles also tend to blow off in sections rather than incurring creases to individual shingles.
Wind blew a section of dimensional shingles off this roof, typical to this type of shingle.
Other Causes of Loss
As mentioned, other causes of loss may mimic the creases, cracks, removal, and other effects of wind. For example, failed sealant strips may occur for a number of reasons, including age, and are not necessarily indicators of wind damage. Here are a few other commonly seen causes of loss that may be misidentified as wind damage.
Attempts to simulate wind damage to shingles often leave evidence. Since wind rarely creates vertical or partial tears, uneven tears with a lack of creasing are more likely to be man-made damage. Prying up shingles often results in tears or creases that don’t extend across the entire shingle.
An uneven tear in a shingle indicates an attempt to manually pry it from the roof.
Vertical racking is a quick, efficient installation method popular among many roofing contractors. However, the National Roofing Contractors Association, the Asphalt Roofing Manufacturers Association, and shingle manufacturers don’t recommend it.
With the vertical racking method, the roofer first installs a column of shingles from the eave to the ridge of the roof. As they install the next adjacent column of shingles, they must lift the outside tabs on the first column to “weave” in the shingles of the second column. This lifting can damage the seal strip. Failure to lift the shingle tabs carefully can cause curls, tears, and other blemishes that may be mistaken for wind damage. In other cases, the shingles are interwoven without lifting the adjacent shingle and a fastener is omitted, reducing the number of nails securing the shingles by 25% and leaving them more vulnerable to wind uplift.
The vertical racking method creates a zipper pattern on the roof and can compromise the sealant strips or concentrate normal expansion and contraction forces.
Manufacturing defects may not be apparent upon installation, but indicators may appear over time that indicate the shingle was compromised from the start. Some of these can mimic the effects of wind damage.
A key difference is the location of the crease or crack, both in the individual shingles and on the whole roof. Manufacturing defects will manifest consistently throughout the roof rather than more prevalently on windward sides and edges. Creases or cracks may also appear in fully sealed shingles, often in the middle, while creases in wind-damaged shingles exhibit near the top.
A crease in the middle of a firmly sealed shingle is one indicator that the damage is due to a manufacturing defect rather than wind.
Identifying the True Cause of Loss
The differences between wind damage and damage from other factors are subtle but many. An inspection is crucial to a proper diagnosis. In addition to knowing what to look for on the roof itself, an expert will include weather data from reliable sources, such as the National Oceanic and Atmospheric Administration, and surrounding indicators in their assessment. Wind strong enough to damage one roof will affect shutters, tree branches, the roofs of surrounding houses, and other collaterals.
Shingle damages can leave a home vulnerable to water intrusion, so identifying the cause and extent of loss is essential to determining next steps. Donan’s roof experts are trusted industry leaders who provide inspections and documented, unbiased conclusions rooted in the scientific process.