Authored by: Rimkus Forensics Marketing Team
Published 6/5/2026
A commercial building sustains roof covering loss during a late-season hurricane. The carrier’s adjuster documents widespread granule displacement. The policyholder’s contractor attributes every deficiency to the storm. A forensic engineer identifies circular granule loss from hail impact alongside uniform erosion from years of ultraviolet (UV) degradation and thermal cycling. Three parties, one roof, and the coverage decision often depends in part on which damage the storm caused and which was already there.
That distinction may influence many coverage disputes in property claims. According to the National Oceanic and Atmospheric Administration’s National Centers for Environmental Information (NOAA NCEI), the U.S. averaged 23 billion-dollar or more weather disasters per year from 2020 through 2024, with annual costs averaging about $149.3 billion.
Forensic storm damage evaluations often focus on separating storm causation from prior deterioration, corroborating claimed exposure with meteorological data, and developing opinions supported by documented observations, testing, and engineering analysis..
Key takeaways: How forensic storm damage evaluations may support claims evaluation
Forensic storm damage evaluation can help assess whether building damage stems from a specific weather event, pre-existing conditions, or both.
What matters most
- Damage patterns, material condition, and failure location relative to pressure zones help differentiate storm causation from prior deterioration
- Storm-event records help assess claimed exposure near a property but cannot confirm conditions at the exact location
- Reports that apply recognized forensic engineering standards may help document methodology, observations, and conclusions in a consistent manner
How investigations typically proceed
- Pre-investigation research assembles weather records, construction history, and maintenance documentation before the site visit
- Field inspection follows a sequential methodology, documenting each building system with photographs, measurements, and instrumentation
- Findings separate observations from opinions and explain how conclusions were reached
Rimkus forensic engineers investigate storm damage causation and prepare forensic engineering reports to support claims evaluation and technical decision-making. Contact us to discuss a claim.
How can investigators distinguish storm damage from pre-existing deterioration?
The single most consequential determination in a storm damage claim is whether observed distress may stem from the reported weather event or from conditions predating it. Not all distress observed following a hurricane is necessarily hurricane related. Conditions such as structural deficiencies, long-term soil movement, inadequate waterproofing, or deferred maintenance can all produce building envelope and structural damage absent any storm event.
Roofing: hail impact versus aging and blistering
Hail impact can fracture the fiberglass mat beneath the granule layer. Granules may displace in circular patterns that correspond to hailstone diameter. On inspection, fresh bright asphalt exposure appears at impact points. Soft spots detectable by hand pressure indicate mat fracture without surface penetration.
Aging and blistering produce a different signature. Granule loss from thermal cycling and UV degradation tends to distribute across the surface rather than concentrating in discrete circles. Raised, dome-shaped blisters typically result from trapped moisture or volatiles. Oxidized, hardened asphalt at granule-loss areas indicates age rather than fresh impact.
Roofing material also shapes how hail damage presents. On metal roofing, hail dents often present as cosmetic rather than functional damage.
Wind uplift versus improper fastening
Wind uplift failures tend to concentrate at aerodynamically critical locations, particularly roof corners and along edges/eaves, where ASCE 7 pressure coefficients are highest compared to interior roof zones. Shingle tabs may lift or detach at windward edges. Fastener pull-through can occur under extreme uplift loads.
Pre-existing fastening deficiencies present a different pattern. Fasteners placed outside the nailing zone, seal strip failure from age or manufacturing defects causing uniform tab lifting across the field, and corroded fasteners indicating long-term exposure typically point to conditions unrelated to storm loading. A wind event may act as the trigger, but an improper nailing pattern or degraded adhesive strip may explain why a roof failed below its rated design capacity.
Water intrusion chronology
Storm-caused intrusion may trace to a specific breach point with no evidence of prior moisture. Chronic pre-existing leakage may show multiple stain layers, biological growth from extended moisture exposure, and staining predating the claimed loss.
The functional versus cosmetic threshold
This distinction often affects how damage is evaluated. Functional damage reduces a roofing material’s water-shedding capability or expected service life. Cosmetic damage affects appearance without impairing performance. Some policy forms address cosmetic damage differently from functional damage. The forensic determination may therefore play an important role in the overall claim evaluation. Where investigators find damage only in cladding and reconstructed wind speeds or hail sizes fall below standard damage thresholds for properly installed assemblies, the finding may indicate pre-existing deficiency or deferred maintenance rather than storm causation.
What does a forensic storm damage assessment include?
Forensic storm damage assessment applies engineering principles to investigate performance problems and document findings for claims evaluation, repair planning, and technical decision-making. Two ASTM International standards relevant to forensic engineering are ASTM E2713-25 (Standard Guide to Forensic Engineering) and ASTM E3176-24 (Standard Guide for Forensic Engineering Expert Reports). In practice, the assessment spans pre-investigation data assembly, a sequenced field inspection, and structural load-path analysis.
Pre-investigation data assembly
Before any site inspection, forensic engineers assemble construction history, maintenance records, meteorological data from National Weather Service storm reports and NOAA databases, and building permit records.
Sequential field inspection
The assessment typically uses multiple inspection passes, with measurements, documentation, and instrumentation readings gathered on successive walks of the same area. This multi-pass approach aims to increase the likelihood that investigators recognize cause-and-effect relationships.
For wind damage, the inspection sequence begins with a walk-around to establish which exterior surfaces wind forces likely affected and to identify the direction from which the storm arrived. Hail damage assessment typically distinguishes functional damage from cosmetic damage and compares hail-caused damage with natural degradation, manufacturing anomalies, installation defects, and mechanical damage.
Structural load path analysis
Wind damage may initiate through loss of roof covering or breaching of the attic envelope. Once wind enters a building, failures can progress along multiple load paths. Tracing this sequence is often important to accurate cause attribution.
How does meteorological data support a storm damage evaluation?
Forensic meteorology reconstructs weather conditions at a particular time and place. The National Weather Service operates a forensic services program that can provide historical weather data for litigation, and the Department of Commerce describes NOAA NCEI weather records as certifiable historical weather records.
Primary data sources
The Next Generation Weather Radar (NEXRAD) network can provide archived products that reconstruct storm paths and precipitation intensity. The Maximum Expected Size of Hail algorithm provides radar-derived hail size estimates based on volume-integrated techniques. Automated Surface Observing System and Automated Weather Observing System networks provide ground-level wind speed, direction, and precipitation measurements at fixed stations. NOAA’s storm events Database documents storms and other significant weather events from January 1950 to the present, including events associated with substantial property damage.
Hard limitations on weather data
Forensic engineers generally should not rely solely on these databases; corroboration from multiple sources is a baseline methodological expectation. Radar-derived hail size estimates indicate potential severity but do not directly measure what reached a specific roof. Physical inspection is often necessary to correlate observed damage with storm data.
What role does expert witness testimony play in storm damage disputes?
When forensic engineering opinions are used in legal proceedings, the opinions are generally expected to be supported by sufficient facts, reliable methods, and reliable application of those methods to the facts of the case.
Methodology under scrutiny
Storm damage investigations are generally strongest when the methodology is documented, supported by engineering principles, and consistently applied to the facts of the assignment.
Report standards
Forensic engineering reports should clearly explain methodology, cite verifiable references, and support conclusions with logical analysis. Field documentation completed before repairs can help preserve perishable evidence; physical conditions change rapidly through weather exposure, emergency repairs, and ongoing deterioration.
Separating storm effects from prior conditions
Forensic storm damage evaluation typically involves physical evidence, meteorological corroboration, and engineering analysis supported by documented methodology and observations. In most claims, investigators work to determine whether observed damage may be associated with a specific storm event or with conditions predating it. That work often requires investigators who can trace failure sequences, interpret damage patterns relative to aerodynamic loading, and clearly document how conclusions were reached.
For organizations seeking forensic investigation support, Contact Rimkus to discuss storm damage evaluation needs.
Frequently asked questions about storm damage evaluation
What are the long-term effects of hail damage on roofing materials?
Hail impact can trigger long-term deterioration by exposing asphalt shingles to accelerated UV degradation and thermal cycling, while micro-cracks and bruises may expand through freeze-thaw cycles and wind-driven rain. Progressive water infiltration can then reach underlayment and decking, contributing over time to rot, insulation degradation, mold growth, and leak pathways at seams, fasteners, flashing, and penetrations.
How do forensic engineers separate storm damage from installation defects or pre-existing conditions?
Forensic engineers compare observed damage against the signatures expected from a storm versus those tied to installation defects, material aging, or deferred maintenance, such as wind uplift concentrated at roof corners and edges versus fasteners placed outside the nailing zone. They also weigh whether reconstructed wind speeds or hail sizes were sufficient to damage a properly installed assembly, since damage below expected thresholds may indicate a pre-existing deficiency rather than the reported event.
Why is meteorological data important in a storm damage evaluation?
Meteorological data helps investigators determine whether the reported storm conditions were capable of producing the observed damage. Weather records, radar data, storm reports, and site-specific observations are often compared with physical evidence to evaluate whether the damage is consistent with the reported storm event.
This article is intended to provide general information and insights into prevailing industry practices. It is not intended to constitute, and should not be relied upon as, legal, technical, or professional advice. The content does not replace consultation with a qualified expert or professional regarding the specific facts and circumstances of any particular matter.