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Wind interacting with a roof is deflected over and around it. As a result, wind uplift pressures occur on the roof. Obvious wind damage involves flipping, creasing, tearing, and removing of shingles from windward roof slopes. This paper will explore those mechanisms as well as what wind damage is not. Inspectors will find this paper useful to diffe...
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... primary modes of asphalt shingle failures occurred during Hurricane Frances: 1) creasing, 2) flipping, 3) tearing/removal, and 4) abrading from flying or falling debris (Fig. 7). It was not uncommon to find multiple modes of failure on a roof or slope. In some instances, entire shingles tore away when the fasteners pulled through the mats. Noone and Blanchard (1993) reported similar modes of failure with asphalt shingles during wind storms. ...
Citations
... Further, unsealed shingles affected the performance of adjacent sealed shingles; wind blowing under the surface edge of an unsealed shingle produces uplift, which increases the surface area exposed to uplift and ultimately leads to the shingles breaking or detaching from the substrate [42]. These conclusions are consistent with previous studies on the effects of wind on asphalt shingles [43]. Additional studies have observed the degradation of structural components over time, specifically in roof-to-wall connections [44]. ...
This study analyzes insurance claim data from an 11-county area in the Florida Panhandle following the landfall of Hurricane Michael. The data includes 1467 non-mobile home structures, with 902 (61.5%) storm-damaged structures in Bay County. The analysis focuses on Wind Mitigation form 1802. Specifically, building design variables were analyzed via linear regression as to their influence on the percent claim loss. The building design variables included total square footage, dwelling construction type, age of the building, roof type, roof cover type, roof deck attachment type, roof to wall attachment, the presence of secondary water resistance (or sealed roof deck), opening protection type, and roof shape. Results show that building design variables for insurance claims have a high predictive value relative to a Category 5 hurricane event. However, the predictive values of building design variables are also dependent on the dwelling’s proximity to the coast, its location relative to the strong or weak side of the storm, the diameter of the storm, and other wind field variables.
... Based on prior field observations, two failure mechanisms related to natural weathering of the sealant strip have been proposed. First, temperature-induced long-term expansion and contraction of the shingle system contributes to the loss of adhesion along a partial length of the sealant strip (Marshall et al. 2010). Dixon et al. (2013) concluded that partial unsealing is common on roofs aged more than 5 years, increasing the shingles' vulnerability to wind damage. ...
Damage assessment surveys performed following the 2004 and 2008 hurricane seasons indicate that the vulnerability of shingle roofs to wind-induced damage increases with age. This paper presents two interrelated experiments on the wind uplift resistance of asphalt shingle seals. The objective is to identify whether and to what extent aging reduces the wind uplift capacity. In the first experiment, asphalt shingles were artificially aged, and the mechanical uplift resistance was measured at discrete intervals. In the second experiment, mechanical uplift tests were performed in situ on ≥9-year-old shingle roofs installed on four central Florida homes. Results from the first experiment demonstrate that heat exposure can reduce uplift resistance along its sealant strip in some products; however, the excess capacity in the bond may be sufficiently large to prevent the mechanical resistance from dropping below the design requirement. Inclusion of ultraviolet and water in the heat-exposure tests did not appreciably change these outcomes. Results from the second experiment, which assessed in-service roofs on single-family homes, support this finding. Overall, the results suggest that aging of the sealant strip may play a secondary role in increasing the vulnerability of shingle roof systems to wind over time. Results from a companion project performed concurrently to this one strongly demonstrated that progressive unsealing (not loss of strength) is a culprit. Improving shingle design to prevent or halt unsealing, without degrading the capacity of the sealant, appears to be the most promising solution to reducing roof cover damage.
... Performance test standards that establish wind ratings of shingles (e.g., ASTM D3161 and ASTM D7158) evaluate new, fully sealed specimens and do not account for long-term changes arising from weathering and aging of the material. Marshall et al. (2010) first addressed the systematic loss of adhesion of in-service sealant strips, finding that unsealing occurs where shingles span the offset end joint of the shingle row (i.e., course) below (Fig. 1). Three-tab shingles are installed with an offset of one-half tab width between courses, thus one-half of the tab width is unsealed and the remaining half is sealed. ...
... More than 99% of the unsealed shingles found on the Florida roofs exhibited the patterns of unsealing reported in Marshall et al. (2010). Partially unsealed shingles were found on eight of 10 three-tab shingle roofs and 11 of 17 laminate shingle roofs for a total of 19 of 27 surveyed roofs (70%). ...
... All surveyed roofs in the Houston, TX metropolitan area contained partially unsealed field shingles exhibiting the same location of unsealing and sealant strip failure mode as the Florida roof surveys and in Marshall et al. (2010). Fig. 5 shows an example of the survey results on a portion of the three-tab roof and one laminate roof. ...
This paper addresses the wind-induced tearing and blow-off of asphalt roofing shingles, which are the most frequently observed forms of residential building damage in hurricanes. Field surveys indicate that in-service asphalt shingle sealant strips can lose adhesion along their leading edge over time, leaving the shingle partially unsealed and susceptible to wind uplift. Two interrelated studies presented in this paper show that unsealing is a naturally occurring process and that unsealed shingles are a contributing cause of shingle roof cover damage in high winds. The first study quantified the number, location, and failure mode of laminate and three-tab style shingle systems installed on residential buildings at 30 sites in Florida and Texas. Systematic patterns of partially unsealed field shingles found on 22 of the 30 roofs resembled spatial patterns of wind-induced shingle damage observed in post-hurricane building performance assessments. As expected, older roofs generally contained more unsealed shingles than newer roofs. The results of the second study link blow-off to partially unsealed shingles. Seventeen ASTM D7158 Class H asphalt shingle roofs were aged outside for nominally one year at the Insurance Institute for Business & Home Safety Research Center and then evaluated in full-scale wind tunnel tests. Partially unsealed field and hip shingles frequently exhibited damage during wind testing, while fully sealed shingles were not damaged unless adjacent, unsealed shingles failed first.
... INTRODUCTION After storm surge damage, roof cover damage is the second largest cause of hurricane-induced residential insurance losses (Liu et al., 2010). Asphalt shingles are the most common type of residential roof system in hurricane prone areas (Marshall, 2010). An asphalt shingle roof system consists of individual shingle sections nailed over wood sheathing and an impermeable water barrier. ...
... Examples of improper nailing include placement too high or too close to the sealant as well as placement too far from the ends of the shingle tabs. Hurricane prone areas typically require six fasteners per shingle, while most roof structures suffering significant damage were observed to have only four.Marshall (2010) noted that out of 11 fiberglass asphalt shingle roofs selected for inspection following Hurricane Frances, ten of them had improper fastening patterns.A damage survey performed by Marshall (2010) after Hurricane Frances in 2004 identified four main factors that influence shingle failure: 1) weathering of shingles, 2) design deficiencies, 3) manufacturing problems, and 4) installation problems. Shingles installed within the last 10 years were observed to perform better overall (RICOWI, 2009). ...
Over 80% of the North American residential (steep-slope) roofs are covered with asphalt shingles. As the water-shedding layer, shingles are exposed to a wide range of weather elements. Weather shocks can negatively impact the field performance of a shingle. Existing North American standards do not provide specifications to quantify properties subjected to the weather shock aging process, and no protocol exists to determine the long-term durability of a shingle. To demonstrate the effects of field and laboratory aging and to develop a framework for the durability of shingles, the National Research Council of Canada undertook a long-term experimental program to evaluate the performance of fiberglass shingles from four different sources. The experimental program studied three aging processes: as-purchased, lab-conditioned, and field-aged. Over 325 specimens were evaluated while focusing on three key properties: tear strength, tensile strength, and fastener pull-through resistance. Properties of the as-purchased samples were used as a baseline to quantify the effect of aging on the shingles’ durability. This paper includes the statistical significance of the measured data. Nevertheless, for simplicity, mean values are used to derive observations and conclusions. Based on those data, the field-aged shingles displayed a maximum reduction of over 50% in tear strength. The majority of the evaluated properties after aging no longer met the minimum requirements that are specified by the North American standards that are referenced in the building codes. Based on these limited data, a framework for a climate-dependent durability index has been proposed for developing a performance-based classification. Demonstration of the framework uses measured mean values. The ongoing experimental program will expand the database and revise, if needed, the presented classifications with data that will be statistically significant.
Asphalt shingle roofs are the most common roof covering in the United States. Major reasons for asphalt shingle popularity are cost, selection, convenience, and availability. Shingle roofs are routinely assessed to determine whether they exhibit damage. The need exists in the U.S. roofing industry for a quick, reliable, and nondestructive test method to identify asphalt shingle seal failures while conducting roof evaluations. Some roofing inspectors use leaf blowers to determine whether asphalt shingles lift when blown, thus identifying them as being unsealed. This is important because unsealed shingles with mat transfer or the presence of debris in the sealant strip adhesive, or both, is a common mode of functional damage to shingle roof coverings observed after a high-wind event. The method's appeal lies in its ease of use and ability to rapidly survey large roof areas. To be rigorous in validating this test method for utilization in roof inspections, it is important to determine whether the leaf blowers cause any damage to roof coverings inadvertently when used as a roof-assessment tool. Interviews of three practitioners of the leaf-blower method were conducted. This information was used to establish an experimental protocol for testing the exposure of model roof assemblies to leaf blowers. Asphalt shingle sealant uplift tests were performed in conformance with ASTM D6381, Standard Test Method for Measurement of Asphalt Shingle Mechanical Uplift Resistance. Results of uplift tests on both “unblown” and leaf-blower “blown” shingles are provided. The test method differs from ASTM D6381 in that the standard tests only a portion of a shingle, whereas our modified method tests the entire shingle sealant strip. Test results with descriptive statistics and analysis of variance for each test roof, shingle type, and a compilation of shingles tested are presented.
Most building damage occurs at relatively low wind speeds, at or below 50 m s–1 (112 mph), as certain components fail, such as doors, windows, chimneys, and roof coverings. Rainwater then enters these openings, leading to interior damage. Structural failures usually begin with the removal of gable end walls, roof decking, and poorly attached roof structures as wind speeds increase; the greatest damage occurs at roof level as wind speeds increase with height above the ground. Internal wind pressure effects can lead to additional, more catastrophic damage, such as the removal of walls and ceilings. It is difficult to measure wind speeds directly on buildings as they would have to be instrumented well in advance of the storm, and there is no guarantee the storm would strike them. Furthermore, flying debris can damage pressure sensors on instrumented buildings. Thus, damage evaluators must infer failure wind speeds indirectly by studying damage left behind in the wake of windstorms. Therefore, it is important that damage evaluators know how buildings are constructed to better understand how they fail. This chapter identifies similar failure modes in residential structures regardless of wind type according to information from more than four decades of storm damage surveys. The information presented herein highlights some of the lessons learned in evaluating storm damage to wood-framed residential structures.
This chapter explains the current understanding of how wind-borne debris becomes airborne. Wind-borne debris is either naturally occurring (e.g., tree limbs, sand, and loose stones) or engineered (e.g., roof sheathing, shingles, and roof ballast such as pavers and aggregate). The chapter discusses the basic theoretical modeling of motion initiation, regardless of source; the key nondimensional parameter that controls motion initiation; and the scaling of laboratory studies to full scale. It also briefly reviews building aerodynamics, including air flow and pressure distributions; the role of parapets in mitigating extreme suction pressures; and potential scaling issues associated with laboratory-scale measurements of pressure coefficients and debris motion initiation. Wind-borne debris from buildings is broadly categorized as either loose laid (e.g., roof pavers and gravel ballast) or fixed (e.g., sheathing and shingles). The chapter further describes the motion initiation of these materials.
