In the event of a tornado, hurricane, or severe tropical storm,the potential for damage to various buildings and civil structuresis significant. This potential increases with various factors, suchas the proximity of the storm event to the structure, age,construction quality, engineering, and materials used inconstruction.

For hurricanes and tropical storms, for example, structuresalong the coastline are at greater risk than structures builtinland. The reason is there can be a substantial wind component ontop of tidal surge and flooding that must be taken intoconsideration. For inland structures, the strength of the wind andtidal surges are less from hurricanes and tropical storms eventhough flooding can still result from heavy rainfalls. Tornadoesmostly impact inland structures in areas deemed to be at higherrisk through analyzing historical weather patterns.

Loss Severity

After these occurrences, damage to structures can range from atotal loss to no damage, with the exception that a concernedpolicyholder thinks his or her property may have sustaineddamage.

Buildings that have been demolished by such a catastrophic eventmay not leave clues from which the claims adjuster or engineer candetermine what portion of the storm resulted from wind/waterinfiltration compared to flooding. Most of the structural forensicwork are to structures that are around 50-percent damaged to nodamage at all.

A claims adjuster may find the insured structured demolished,while neighboring structures remain intact and suffer minimaldamage. Why is this? Could there be a construction defect thatallowed the wind and/or flood to damage the structure? Certaininvestigate tips and research can help claims professionalsaccurately answer these types of questions.

Pre-existing Conditions

For wind-related events to buildings, one of the first questionsthat should be raised is the following:

How fast was the wind?

Answers can be found through common weather-related Web sitesand the National Oceanic andAtmospheric Administration (NOAA). It is important to useseveral different weather stations that encompass the subjectproperty, and either average the data or use conservativevalues.

How old is the structure?

This question is relevant because an older structure may notsustain the impact of high winds as well as a newly constructedbuilding. As building codes become more defined, loading conditionsfor wind and snow have generally increased. For example, a newbuilding along the coast may be designed for 120-mph winds, whereasa 40-year-old building may have only had to be designed for 80-mphwinds. Sometimes, though, the exact opposite is true.Sometimes older buildings sustain less damage while newer (andcommonly lighter) buildings sustain more damage. Thiscondition is the use of bigger, thicker materials (which are oftenheavier) that can help restrict the movement of a structure.

Where is the damage observed?

This question should be answered (when dealing with wind-relatedmatters) from the top down. Generally speaking, wind affectsbuildings the higher they stand off the ground, possibly leavingblown-off roofs and no observed damage to first-floor walls or thefoundation. Lighter gauged materials such as roof vents, shutters,and roof coverings along the roof perimeter and ridges willgenerally show more damage than along the inner face.

How was the building constructed?

Most wood-framed buildings use common roof lumber that generallyhave provisions that must be met to ensure the building does notget blown down. The use of hurricane clips, straps, and anchors areutilized along the roof-to-wall, wall-to-wall, wall-to-floor, andfloor-to-foundation connections. Any of these areas missingpossible load-transfer provisions may result in damage caused froma wind incident that could have been prevented.

If a building is under construction when a loss occurs, thereare usually provisions and codes that are in force to protect thebuilding while it is under construction. The general contractor isusually responsible for protecting the structure to preventpossible damage. The use of temporary bracing and methods toprotect against the elements is a major component to ensurefailures do not occur.

(Building failure from a wind incident due to lack of temporarybracing.)

An example of this condition has been noticed after a tornadooccurred in an area that does not experience tornadoes. Because ofthe lack of tornadoes, some contractors and building officials maynot have been as concerned in ensuring these conditions are met. Ina particular development that was constructed using severaldifferent contractors, some common themes developed where certainbuildings sustained more damage than others standing closer to thetornado path.

Other inspections of the neighboring properties indicated thathurricane clips and straps were utilized, as indicated below, whichhelp minimize the overall structural damage.

The end result may help the claim examiner's decision topossibly pursue a subrogation claim against the contractor orbuilder for failure to install these clips, which would haveprevented the building from being an almost total loss.

The aftereffects of a hurricane can causedifficult assessments and/or segregating damage that was caused bywind and water infiltration. While damage to roof areas is commonlyattributable to wind, areas along the first and second floors couldbe damaged by wind/water and/or flood/tidal surges that couldaffect the overall scope and cost of the claim.

Weather-related losses are another area where a civil engineercan greatly assist with claim investigations. The wreckage from acatastrophic hurricane strike can devastate whole cities and costinsurers and reinsurers hundreds of millions of dollars. The commonquestion tends to be what damage was caused by wind and rain andwhat damage was caused by flood. A civil engineer can provide asite inspection documenting crucial information to help separatethese damages.

Water-mark lines along building walls, trees, and hills shouldalways be inspected. Impact strikes indicative of objects crashingaround during a tidal-surge period are major indicators of flooddamage. Usually, wind damage affects weaker materials such asvinyl siding and asphalt-shingled roofs. Wind forces are strongestalong building corners and edges and can damage structures fromboth a positive and negative (vacuum) pressure. If a building isentirely leveled without anything left to inspect, civil engineerscan also estimate damage that could have been caused by wind, rain,and flood based on storm weather data and flood-survey maps.

The following tips can be used to help evaluate the overalldamage and indicate if the cause is primarily wind/water intrusionor surge:

1. Determine and document any evidence of mold: Upper floors mayindicate point of water intrusion from wind/water intrusion entry.Bathroom areas may indicate prior indication of a moisture/humidityproblem from venting.
2. Examine the sheetrock in the interior of the building and notedistressed areas of the sheetrock (upper floors may indicate windand/or surge if cracking is throughout).
3. Warping damage on floors and opened up ceilings from below (canindicate surge).
4. Warping flooring around base of windows may indicate waterintrusion.
5. Identify how high the water was in the home. Look for highwater marks on walls or debris lines around the property oradjacent structures (indicates surge).
6. Identify the home's base flood elevation (from FEMA) andoverall ground elevation (which can indicate overall flood/waterlevels within the home).

When structural damage is suspected, a civil engineer candetermine if a foundation crack was caused by constructionactivities by visually observing within the cracks for details suchas the color, sharp edges, the presence of any dust, debris, and/orpaint. Additionally, a civil engineer will inspect for evidence ofbuilding settlement, soil conditions, and temperature changeswithin building materials, as well as examining pre-constructiondamage surveys and seismographs.