Wind and Hail Damage to Commercial Roofing

Forensic Engineering Fire Investigations Environmental Consulting Specialty & Consulting Services

Wind and Hail Damage to Commercial Roofing

Chad T. Williams, P.E., EVS/R®Senior Engineer, EFI Global, Inc.Oklahoma Certificate of Authorization 4900Expiration: June 30, 2018

National Tornado SummitOklahoma City, OklahomaFebruary 27, 2018

May 20, 2013, Moore, Oklahoma Tornado

Introduction Forensic Engineering Overview Weather Data Site Conditions Indicative of Storm Damage Functional Damage Hail and Wind Damage to Common Types of Commercial Roofing.

Single Ply Membranes SPF Roof Coatings Metal Panel Built-Up-Roofing (Coated and Ballasted) Modified Bitumen Cap Sheets Asphalt-Composition Shingles

Questions? Summary

Light Commercial and Residential Earthquake Evaluations

Chad T. Williams, P.E., EVS/R®, Senior Engineer (Property Forensics)

Bachelors of Science in Civil Engineering 2001 from the University of Oklahoma(Primary Areas of Study: Civil, Geotechnical and Structural).

Licensed Professional Engineer: Alabama, Arkansas, Colorado, Iowa, Kansas,Mississippi, Missouri, Nebraska (Civil), New Mexico, Oklahoma (Civil andGeotechnical), South Dakota, Texas, and Wyoming.

9 Years of Operational and Forensic Engineering Experience. 15 Years ofEngineering Experience.

NCEES Model Law Engineer Completed more than 1,000 individual property evaluations. National Society of Professional Engineers House of Delegates Member for

Oklahoma. Member: American Society of Civil Engineers, Oklahoma Society of Professional

Engineers, National Society of Professional Engineers. Associate Member: National Academy of Forensic Engineers.


What is Forensic Engineering?


The National Academy of Forensic Engineers (NAFE) defines Forensic Engineering as:

“The application of the art and science ofengineering in matters which are in, or maypossibly relate to, the jurisprudence system,inclusive of alternative dispute resolution.“

Forensic Engineering

The American Society of Civil Engineers (ASCE) defines Forensic Engineering as:

“…the application of engineering principles to the investigationof failures or other performance problems. Forensicengineering also involves testimony on the findings of theseinvestigations before a court of law or other judicial forum,when required.Failures are not all catastrophic, such as when a building orbridge collapses, but include facilities or parts of facilities thatdo not perform as intended by the owner, design professional,or constructor.”


In more direct terms, Forensic Engineers are involved toinvestigate a situation and determine:

What happened? When did it happen? How much damage is attributable to the specific

situation and/or cause of loss? Why did it happen? Were there mitigating or exacerbating factors to the

cause of loss?


Property Forensic Engineering


Structural Design Engineering

Geotechnical (Soils) Engineering

Material Science Construction

Management

Construction Methods

and Codes

Civil Engineering

Failure Analysis

Other Areas/Experience

Roof Evaluation Process

A typical roof evaluation will include:– Review of weather data (multiple sources), property data (county

assessor/appraiser or commercial websites), aerial images from Google Earth,and other data related to the structure.

– Interview/discussions with the owner’s or other persons that were presentduring the storm event. For commercial properties, the employees may havemore information about a given weather event and the history of a building thanthe owner’s representative.

– The evaluation of the exterior wall elevations of the building and the site forindications of weather events.

– The evaluation of the interior of the building for indications of deck damage,skylights, or framing damage/deterioration.

– The physical access and evaluation of the roof surfaces.– Verbal summary of observations– Written Report to the retaining party.


A typical roof evaluation will include:– Review of weather date (multiple sources), property data (county


– Interview/discussions with the owner’s or other persons that were presentduring the storm event. For commercial properties, the employees may havemore information about a give weather event and the history of a building thanthe owner’s representative.




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A typical roof evaluation will include:– Review of weather date (multiple sources), property data (county


– Interview/discussions with the owner’s or other persons that were presentduring the storm event. For commercial properties, the employees may havemore information about a give weather event and the history of a building thanthe owner’s representative.




Fiberglass panel skylights, rotten/damaged framing, corroded/deteriorated decking, and

other conditions may be dangerous and should be identified before accessing a roof.

Sources of Weather Data

No Cost Governmental Sources– National Weather Service Local Offices– NOAA Storm Prediction Center (SPC)– National Center for Environmental Information

(NCEI) Fee-for-service Sources


No Cost Governmental Sources– National Weather Service Local Offices– NOAA Storm Prediction Center (SPC)– National Center for Environmental Information

(NCEI) Fee-for-service Sources In this section, the reference storm is the

August 6, 2017, Tornado that occurred in Tulsa, Oklahoma.


Local National Weather Service Office(https://noaa.maps.arcgis.com/apps/MapJournal/index.html?appid=c816a5369e204f04ad77ad0b8a11353c)

Actual websites vary by event and/or NWS office. Local reports are typically created for larger,

stronger, or more significant weather events. Details will vary depending on the office and the

severity of the event.


NWS Tulsa, Oklahoma August 6, 2017, Tornado


NOAA Storm Prediction Center (SPC) (https://www.spc.noaa.gov/)

Summary of NWS ‘Official’ Storm Reports Data Provided on an daily basis

– Data starts a Noon on the day listed and extends to noon the following day.

– Data is dependent on observations and reports. – Data may not indicate events in rural or sparsely

populated areas.


SPC August 6, 2017


National Centers for Environmental Information (NCEI) (https://www.ncei.noaa.gov/)

Searchable Summary of ‘Official’ Storm Reports


NCEI Tulsa, Oklahoma August 6, 2017, Tornado


NWS Norman: May 20, 2013 Moore Tornado


NWS Norman: May 20, 2013 Moore Tornado

A straight line interpolation of the

start/stop points would miss the damage path.


Fee-for-Service Weather Data Sources:– Typically are based on radar interpolation of radar data using proprietary

algorithms.– The algorithms may or may not have been correlated to observations on the

ground.– Wind currents, storm convection, and other factors may alter the point where

hail actually strikes the ground.– Typically used to indicate that a thunderstorm event capable of producing a

given type of event may have occurred at the site.– Spatter, marks, downed tree limbs and other conditions present at the site as

necessary to confirm or refute radar algorithms data.– Precision for the size of hail and the point where it reaches the ground will vary

widely.

https://scijinks.gov/review/rain/hail-formation-large.jpg



Weather Data (whether governmental orcommercial) will commonly report the largestor worst condition perceived. For hail, it willnot address the density of the largest hail or ifthat report is representative of the event as awhole at that specific location. Non-instrumented wind data can have similarchallenges.

Site Conditions Indicative of Hail and/or High Winds


Indications of Recent Hail: SpatterMarks to wood Surfaces– Typically Comet Shaped or circular.– Fade or weather over time

(commonly visible for about a year).– Commonly Measure about 80% of

the diameter of the source hail.


Spatter marks are the displacement ofmicrobes, oxides, and grime fromsurfaces at the point of a hail stoneimpact. Depending on the underlyinglayer, they may appear lighter or darker.





Spatter marks can assist in determiningthe directionality of a hail event andspatter marks will be commonly bepresent on specific fence exposuresbut not all.








Spatter marks indicate the presenceand size of hail. The presence ofspatter marks does not necessarilyindicate functional damage to surfaces.


Indications of Recent Hail: SpatterMarks to Painted Metal Panels, Poles,etc.– Typically Comet Shaped or circular– Fade or weather over time

(commonly visible for about a year).


Indications of Recent Hail: SpatterMarks to Painted Metal Panels, Poles,etc.– Typically Comet Shaped or circular– Fade or weather over time

(commonly visible for about a year).

Spatter marks on metal surfaces may or may not coincide with deformations to

the metal panel surfaces. As such, they may not indicate functional damage.


Hail Indentions to Soft Metal:-Hail indentions to gutters are dominantlyvertical in nature (from above).-Vertical gutter lines are commonly dentedby flying debris from mowing activities,recreational balls, vehicle impacts, etc.and may be dented by hail.


Hail Indentions to Soft Metal: Roof Vents- Indentions to roof vents may indicate

more than one hail event.- Without recent spatter marks, it may

not be possible to correlate to aspecific event.


Hail Fractures/Penetrations to VinylSiding:- Fractures/penetrations are commonly

highly directional.- The presence of fractures/penetrations

only along the lower edges of vinyl isnot consistent with hail

Site Conditions Indicative of Storm Damage

Wind Damage to Trees:- Often by the time Forensic

Engineers visit a given site,damaged or failed trees have beenremoved.

- Indications of fresh wood arereviewed at stumps

- Discuss site specifics with owner.

Site Conditions Indicative of Storm Damage

Wind Damage to Trees:- Often by the time Forensic

Engineers visit a given site,damaged or failed trees have beenremoved.

- Indications of fresh wood arereviewed at stumps

- Discuss site specifics with owner.

The presence of trees close to abuilding may result in cyclical andongoing abrasions to the roof surfacesthat may be unrelated to a given stormevent.

Functional Damage

Functional Damage from wind and/or hail is defined assudden change in the roof system that detrimentally altersthe function of the roof. The function of roofing systems areto:

• To shed water and to prevent water from penetratinginto the building.

• To perform its energy related function to the extent thatone is present.

• To not become wind-borne.• To last through it’s intended service life.

Functional damage may present differently based on thetypes of roofing system present.

Single-Ply Membranes

Hail Damage to a single ply membranecommonly occurs at a point of impactwhere the membrane is stretched andfractured.Rigid underlayment's immediately belowthe membrane result in greater resistanceto fracturing compared to foam sheeting.


Hail Damage to a single ply membranecommonly occurs at a point of impactwhere the membrane is stretched andfractured.Rigid underlayment's immediately belowthe membrane result in greater resistanceto fracturing compared to foam sheeting.

The most common areas for hailfractures are along parapet wallsand raised gutters for rooftop HVACunits. This is due to a change in thesupport condition.


Wind Damage to single-ply membranescommonly start with the failure of theparapet wall cap. This then allows air toact on the back side of the parapet walls.As the wind continues to act on theparapet walls, the single-ply membranecan pull from the interior face of theparapet wall and/or the roof decking.


Wind Damage:- Detached roof sections will

commonly lift and flutter undercontinued winds.

- Over time, the detached area willcommonly expand further into theroof until the parapet cap detachesor the membrane tears.


Long-term Deterioration of single plymembranes commonly occurs due to aloss of plasticizers and contraction ofmaterials.


Long-term Deterioration of single plymembranes commonly occurs due to aloss of plasticizers and contraction ofmaterials.

Contraction and stretching of the roofmembrane is not typically consistentwith wind. The resulting openingsmay allow for water to leak past theroof surface.


Long-term deterioration may allowfor single-ply membranes tobecome brittle and to split. Whilethis roof membrane was damagedby hail, numerous small andsemicircular cracks (withoutspatter marks) were present.


Long-term deterioration may allowfor single-ply membranes tobecome brittle and to split. Whilethis roof membrane was damagedby hail, numerous small andsemicircular cracks (withoutspatter marks) were present.

Many of the cracks measured less than ¼inch and extended fully through themembrane allow water to seep through theroof surface.


Often, circular marks that are occurring in a pattern are identified as ‘hail damage’. It is important to view the overall pattern of the marks as circular marks, such as these,

are indicative of the presence of fasteners and are not hail damage.

SPF Roof Coatings

Hail Damage:- Commonly occur as circular or semi-

circular fractures through the membrane.- May occur as concentric series of circular

factures with a ‘spiders web’ type ofappearance.

- Fractures commonly deform into thefoam.

SPF Roof Coatings

Hail Damage:- Commonly occur as circular or semi-

circular fractures through the membrane.- May occur as concentric series of circular

factures with a ‘spiders web’ type ofappearance.

- Fractures commonly deform into thefoam.

Foam exposed to sunlight will rapidlydarken in color and embrittleeventually crumbling to a sand likeconsistency. Water is commonlypresent under fractures orpenetrations.

SPF Roof Coatings

Blisters: Typically occur as a result of the presence ofmoisture, oils or other contaminations at the time ofconstruction of the roof. Blisters to the SPF are notconsistent with weather related causes.

Metal Panel Roof Surfaces

Functional damage as a result of hailimpact will occur as penetrations of themetal or the deformation of the side oroverlap panels. Functional damage canalso occur as a result of thecracking/splitting of the surface coatingshowever, this is uncommon.

Forensic Engineers may or may notknow of whether


Indentions from hail along overlap seamsthat separate or pull apart the seal stripbetween the metal panels may allow winddriven rain and/or concentrated water flowsto penetrate the roof surface. As such,indentions such as these are considered tobe functional damage


Wind Damage: Failure along the eaves and hips andsubsequent failure within the field of the roof.

Hurricanes Irma and Maria, US Virgin Islands


Wind blown flying debris will commonlypunch through, slice along, or abrademetal panel roof surfaces. The tearing ofthe metal is considered to be functionaldamage. Abrasions that penetrate thesurface coatings are considered to befunctional damage.

Hurricanes Irma and Maria, US Virgin Islands


Foot Fall on a metal panel roof surface canresult in localized load buckling of the primaryribs. For this reason it is important to avoidstepping on the primary ribs. Localized loadbuckles often occur along line or paths on aroof.


Foot Fall on a metal panel roof surface canresult in localized load buckling of the primaryribs. For this reason it is important to avoidstepping on the primary ribs. Localized loadbuckles often occur along line or paths on aroof.

Linear load buckles from foot fall do not

have the random pattern of hail.

Built-Up Roof Surfaces

The most vulnerable sections of builtup roofs are located along thetransitions along the perimeter parapetwalls or curbs for rooftop HVAC unit.Hail damage at this location willcommonly result in bruises orpenetrations of weathers transitionflashing.


The most vulnerable sections of builtup roofs are located along thetransitions along the perimeter parapetwalls or curbs for rooftop HVAC unit.Hail damage at this location willcommonly result in bruises orpenetrations of weathers transitionflashing.

Stone surfaced built up roofs are resistantto hail damage. When suspected, roofcores and laboratory testing are commonlyneeded to confirm splits to the roofingfelts.


Hail impacts to asphalt flood coated roofsurfaces commonly result in fractures withconcentric circles and/or: semi-circularsplits. Alligator cracking, as observed inthese images are due to weathering ofasphalts over time. Cracked asphaltflood coatings may be detached due tothe freezing of accumulated water.

Hail stones can displace the crackedasphalt surface exposing the underlyingfelts. It is necessary to review the overallpattern of asphalt displacement andweather date to determine cause.


Hail Damage to Surface Coatings can befractured and/or displaced by hailimpacts. In this situation, the roofsections extending over an expansionhad less support than that fully in contactwith the deck. The fractured anddisplaced sections of the surface coatingwere considered to be functional damage.- .

Modified Bitumen Cap Sheets

Hail Damage to modified bitumen cap sheettypically results in concentrated areas ofgranule loss and is dependent on thesubstrate. Modified bitumen cap sheetswill commonly lose granules during theirservice life. Generalized granule loss is notconsistent with hail.


Wind Damage to a modified bitumen capsheet built-up roof will typically initiatealong the outside edge of the roof. Thisallows for the roof to lift and/or flip due towind. This type of failure can also allowfor water to penetrate into the roofresulting in a later failure.


Blisters commonly occur as a result ofinadequate bonding of roof componentsduring the original construction and canoccur as a result of water penetrationsduring the service life of the roof. For ablister to be storm related, there is typicallya penetration of the roof surface or flashing.

Asphalt-Composition Shingles

Hail damage to asphalt-compositionshingles occurs when a hail stonestrikes the surface and stretches andfractures the mat. This processdisplaces granules along the perimeterof the impact and through the middle.The result is a hail bruise to the shingle.

Hail bruises to asphalt-composition shinglescommonly have the feeling of a bruise to anapple.


Large hail can penetrate through theasphalt-composition roof shingles andpunch holes through roof decking.


Roof surfaces may show hail damagefrom more than a single event. In thisimage, the exposed asphalts of an olderbruise has greyed and granules havebeen displaced. The recent bruising(less than 30 days at the time of theevaluation) remained dark black.


Wind damage to three-tab style asphaltcomposition shingles typically includedhinged and/or displaced shingle tabs.Hinging commonly occurs at the top ofthe tab immediately below the bottomedge of the overlying shingle.


Blisters:- Characterized by near vertical walls

along the perimeter of the mark.- Tend to include full thickness

displacement.- Commonly measure less than ½ inch.


Blisters:- Characterized by near vertical walls

along the perimeter of the mark.- Tend to include full thickness

displacement.- Commonly measure less than ½ inch.

Blisters commonly occur as a result ofexcessive heat due to insufficient roofventilation. Blisters are not consistent withhail impacts.

Questions?

In this presentation, a general overview of the type of workperformed by a forensic engineer was presented. Theinformation is not exhaustive and did not include detailedinformation about how the work is performed, or the sourcesof data utilized.

The examples shown have been simplified for the clarity ofthe presentation and are not representative of any specificprevious assignment by the engineer or EFI Global, Inc.

Forensic Engineers report the conditions observed in a givencircumstance but do not make coverage decisions and do notconsider the application of coverage as part of their work.

Disclaimer

Contact Information:Chad T. Williams, P.E., EVS/R®Senior Engineer (Property Forensics)EFI Global, [email protected] Phone (918) 480-0433Office Phone (405) 521-2848


Wind and Hail Damage to Commercial Roofing

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