Field Investigation and Evaluation of Roofing Systems Following a Major Wind Event

To view the figures and tables associated with this article, please refer to the flipbook above.

As Tampa, Florida, marks one and a half years since the unprecedented back-to-back hurricanes of 2024, the structural engineering community continues to analyze how hurricanes expose intrinsic vulnerabilities in the region’s building envelope systems. A forensic assessment of more than 30 residential structures across Hillsborough, Pinellas, Sarasota, and Manatee counties revealed both remarkable strengths and critical weaknesses in roofing assemblies. These findings have major implications for the resiliency and sustainability of coastal communities facing increasingly intense wind events (Emanuel, K., 2005. Increasing destructiveness of tropical cyclones over the past 30 years. Nature 436: 686–688).

Hurricane Helene made landfall as a Category 4 system along the eastern Gulf Coast near Tampa on September 26, 2024. According to the National Hurricane Center (NHC), gusts penetrated far inland due to the storm’s fast forward motion, with the strongest land-measured sustained wind of approximately 91 miles per hour (mph) recorded near Live Oak, Florida, and with maximum aircraft recorded sustained winds of 140 mph. Two weeks later, Hurricane Milton made landfall on Siesta Key (approximately 50 miles south of the Tampa region) as a Category 3 system, delivering sustained winds up to 91 mph and gusts approaching 107 mph along Venice Beach with maximum aircraft recorded sustained winds of 120 mph.

The consecutive nature of these events created a unique forensic scenario: structures were exposed to two major loading cycles within a short period of time—allowing the engineering teams to differentiate between pre-existing vulnerabilities, storm-induced damage, and cumulative deterioration across both events.

Conducting a systematic and objective forensic investigation is crucial to ensure the integrity of the investigation, while ensuring accurate evidence is gathered in a safe and ethical manner. Post-event investigations were conducted in accordance with ASTM E2713-18 Standard Guide to Forensic Engineering, which provides guidelines on the role and qualification of engineers conducting forensic evaluations, including:

Wind pressures were evaluated for Components and Cladding (C&C) using ASCE 7-22 provisions, with particular attention to roof discontinuity zones where aerodynamic flow separation increases uplift demands.

A thorough understanding of wind effects on structures, as well as design and installation practices, enables investigators to effectively gather relevant field evidence, define minimum performance expectations, and accurately reconstruct and assess observed conditions using relevant engineering principles. The Florida Building Code (FBC) requirements and ASCE 7-22 wind design loads, were used to estimate the wind demand after each event. It’s important to mention, that current code was used for the purpose of this research to understand how the requirements of current code would affect the performance of roof assemblies and to determine whether damage was caused by wind speeds exceeding design level forces, under-designed roofing assemblies, or installation deficiencies.

When wind interacts with a building, both positive and negative (i.e., suction) pressures occur simultaneously. However, wind pressure on a structure is not uniform pressure. Wind pressure will increase as the path of wind encounters discontinuities in a structure due to aerodynamic effects, called flow separation. Flow separation around a building occurs when wind detaches from its surface, especially at sharp edges, creating turbulent, low-pressure zones (separation bubbles) that can cause significant uplift forces. Discontinuities include hips, ridges, corners, valleys, and edges in the roof covering as well as corners on the wall surfaces.

This behavior of wind forces is recognized by applicable building codes that require these areas to be designed to resist higher forces for a given wind speed compared to the main body of the roof. ASCE 7-22 partitions roof areas into zones:

The areas of a structure that experience an increase in wind pressure as a result of the referenced discontinuities will likely exhibit wind related damage before the remaining areas of a structure that are subjected to lower wind pressures.

The exposure of the building to wind forces also plays a significant role in the wind forces a building experiences. Buildings in Exposure D zones experienced higher pressures.
Florida’s building code differs from many other U.S. jurisdictions due to its explicit focus on high-wind events, wind-borne debris regions, and repeated hurricane exposure. In addition to the ASCE 7-22 requirements, Florida jurisdictions typically incorporate:

Higher mapped design wind speeds: Florida’s High Velocity Hurricane Zone (HVHZ) designation established by the FBC apply to Miami-Dade County and Broward County. However, most of Tampa falls into areas of Wind-Born Debris Regions (WBDR) with ultimate design wind speeds of 150 mph.

Product approval systems: All building envelope products within the HVHZ must have a Notice of Acceptance (NOA) provided by the jurisdiction. All exterior opening products used within a WBDR are required to have a Florida Product Approval (FPA) or NOA approval.

Asphalt Composition Shingles—Installation Requirements

Asphalt shingles must be tested and classified for wind resistance under ASTM D7158 Standard Test Method for Wind Resistance of Asphalt Shingles and/or ASTM D3161 Standard Test Method for Wind Resistance of Steep Slope Roofing Products and per manufacturer’s recommendation. Proper installation typically requires:

For shingle detachment to occur, wind uplift forces must exceed both the adhesive bond strength and nail withdrawal resistance.

F_uplift>F_sealantbond+F_{nailwithdrawal}

Concrete and Clay Tile Roofing—Installation Requirements

The Florida Building Code permits concrete and clay tile installation using:

The installation of concrete and clay roof tiles and their wind resistance is governed by the Florida High Wind Concrete & Clay Tile Installation Manual (FRSA/TRI) 5th Edition Manual and Section R905.3 of the Florida Building Code. Tile uplift resistance per FRSA/TRI 5th Edition Manual is:

R=W+A∙ΔP

Where:
R = Resistance of tile-fastener assembly
W = Self-weight of tile
A = Tributary area of tile
ΔP = Differential pressure

To cause the detachment of an individual roof tile secured to the substrate with mechanical fasteners (typically two nails or screws per tile) or to cause the de-bonding of an individual roof tile secured with cementitious mortar or foam adhesive, the wind uplift force must first overcome the dead weight of the tile and be of sufficient additional magnitude to break the tile, fasteners and/or the bond between the cementitious mortar or foam adhesive used to secure the tile to the substrate.

Therefore, if wind forces were to affect a tile to the degree necessary to cause detachment, the tile would be significantly displaced from its installed location and/or blown off the roof.

Metal Roof Panels—Installation Requirements

Metal roofing systems consist of large mechanically fastened metal panels or sheets that create a continuous barrier to wind. Metal roofing systems rely on:

When installed correctly, metal panels function as integrated, mechanically secured strong, lightweight roof covering systems that efficiently resist wind uplift while providing accommodation for thermal expansion and contraction without stressing the interlocking mechanism.

Wind damage to a metal roof panel is typically characterized by displaced, partially detached, or missing panels, as well as impacted (wind debris) panels.

Single Ply Roofing—Installation Requirements

Single-ply roofing systems, such as Thermoplastic Polyolefin (TPO), Polyvinyl Chloride (PVC), or Ethylene Propylene Diene Monomer (EPDM), are flexible membrane systems designed for low-slope roof assemblies. Proper installation is critical to ensure durability, water tightness, and wind resistance requiring the following:

The installation of single-ply roofing systems is governed by the manufacturer’s recommendation and the NRCA (National Roofing Contractors Association). ASTM Standards (ASTM D4434, ASTM D6878 and ASTM D4637) define material properties and testing requirements for such systems.

The detachment of a single-ply roofing membrane under wind forces is usually caused by a combination of improper installation (poor substrate preparation, incomplete seam welding) membrane defects, and wind loads that exceed the system’s design capacity. When installed correctly, single-ply systems provide a continuous, wind-resistant roof system suitable for low-slope applications.

Recent updates to the 2023 FBC, Residential (Eighth Edition) have introduced more stringent requirements for roof sheathing thickness in high-wind regions. Under Section R803.2.2, the minimum thickness and required panel span rating for wood structural panel roof sheathing are established based on design wind speed and exposure category, with areas subject to higher wind loads (such as those with ultimate design wind speeds of 140 mph or greater) generally requiring a 19/32-inch (nominal 5/8 inch) panel to meet uplift resistance criteria. In less severe wind zones, thinner panels (such as 15/32-inch) may be permitted; however, each thickness must be installed with the appropriate fasteners and spacing outlined in Section R803.2.3.1 to ensure adequate attachment and resistance to wind uplift forces.

ASCE 7‑22 C&C design pressures were used to evaluate and compare the maximum wind loads that roof and wall components of a building would be expected to resist, based on code-specified wind speeds versus the maximum observed wind speeds. For illustrative purposes, Table 1 summarizes the ASCE 7‑22 C&C design pressures calculated for a basic wind speed of 150 mph with the following building parameters:

The values presented are representative design pressures for low-rise residential roofs and walls, providing a preliminary reference for evaluating uplift and lateral wind loads in accordance with ASCE 7‑22 guidelines.

Asphalt Composition Shingles

Typical wind-related damage included missing, torn, or creased shingles. Creasing indicated uplift forces sufficient to bend tabs without full detachment.

In all observed instances, the observed damage was located within zone 2 of the roof, recognized by applicable building codes as an area that requires to be designed to resist higher forces for a given wind speed compared to the main body of the roof (Tables 1-3).

Concrete and Clay Tile Roofing

Observed damage primarily involved displaced or broken tiles, often due to wind-borne debris rather than direct uplift failure. Performance varied by attachment method:

Metal Roof Panels

Metal roofing systems generally performed well under wind loading. The damage observed was primarily associated with impact from falling trees and wind-borne debris, leading to panel deformation and water intrusion through the damaged underlayment rather than uplift failure.

Single Ply Roofing

Single ply roofing systems performed well under wind loading. The damage observed was primarily associated with long-term deterioration (cracked and deteriorated sealant at intersection between roof and elevated walls), leading to water intrusion rather than uplift failure.

Asphalt Composition Shingles:

Shingle creasing is a classic indicator of uplift force sufficient to bend the tab but not fully tear the shingle.

The most common construction deficiencies found were:

Concrete and Clay Tile Roofing

The following damage was not attributable to elevated wind forces but to deferred maintenance, aging and/or construction deficiencies:

Manufacturing and/or installation defects can also be exhibited as cracks at the tile corner. These defects are the result of deficiencies in the uniformity of the material mix, and the mechanics of pressing or extruding processes, which causes an isolated weakness in the tile and/or installation without provision for thermal expansion and contraction.

It is important to mention that long–term and repeated exposure to elevated wind forces, often less than design wind speeds, will impact the roof covering that has been deficiently installed. Other conditions such as quality and age of the materials, directionality of the winds, extent of UV exposure (e.g., shaded roof surfaces vs. exposed roof surfaces), thermal cycling, and other factors (e.g., debris covered surfaces), will affect the performance and extent of wind-related damage to the roof coverings.

The forensic analysis following Hurricanes Helene and Milton confirms that proper installation, inspection, and maintenance are the most critical factors in roofing system performance. Even when exposed to near-design wind speeds and multiple wind events:

Strengthening inspection protocols during construction, improving installer training, and enforcing Florida’s product approval and fastening requirements will continue to enhance building resilience and reduce repeat wind losses across coastal communities.

About the Author

Maria Martinez, PE, is a licensed Professional Engineer with over 10 years of experience in structural engineering, specializing in forensic investigations and the evaluation of existing structures. Her practice centers on diagnosing structural distress, identifying damage mechanisms, and developing repair and rehabilitation strategies for residential and commercial buildings.