David P. Amori, PE, RRC, is the senior district manager atEFI Global, Inc.

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Building envelope assessments for storm-related damage is a normal part of job for the propertyadjuster and forensic consultant. The assessment of storm-related damage inevitably becomes aquestion of whether the observed condition pre-dates the storm oris the result of sudden and recent event. In fact, the question mayvery well be, “Did the observed condition exist during or evenbefore the building was constructed; is the condition the result ofa construction or design related defect?”

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Buildings are fairly straightforward. With four walls and a lid,there isn't much really that can go wrong. Right? Actually,buildings are doing quite a bit even though it appears that theyare sitting there, blocking the view of the sunset. Even a simplebuilding is, in actuality, a somewhat sophisticated “machine.” Itkeeps the wind and rain out, hopefully. A building reflectsradiation, insulates from temperature fluctuations, maintains aninternal environment, cycles gas, and manages vaportransmissions.

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It also transfers gravity—the weight of material, people,equipment, and furniture—and lateral (wind and earthquakes) loadssafely to the foundation. This modern machine distributes freshwater and electricity and expels waste. It can detect smoke orunauthorized entry and even call for help. And that is asimple building. All these things happenwhen an amazing sequence of events comes together out of seeming(and literal) chaos through the procurement process resulting in afinished building. What can go wrong?

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Defects Happen

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Construction is seldom performed by one entity. Usually there isa general contractor whose job is to “buy-out” (subcontract) theconstruction of the building. Typically there would be somewhere inthe neighborhood of 25 subcontractors and maybe 10 to 15 suppliers,all of which are orchestrated through the general contractor toprovide what is, in some cases, an artistic interpretation of thedesign documents. Each subcontractor has work that will interfacewith the work of another. The opportunities for overlaps and,worse, holes in the scope of work are many. Multiply that withmisinterpretations of and flaws in the design, material defects,and things can go seriously wrong. By the way, none of theopportunities for a construction defect mentioned above includemalintent. Defects can happen with honest, well-meaningprofessionals.

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So how does one sort a construction defect from storm-relateddamage? A claims professional can make this determination in acouple of ways: One is to endeavor to understand the layers ofphysics associated with a building and identify the root cause ofan observed condition based on the current understanding of thephysical world. The other is to look for manifestation of acondition in a manner that would be consistent with an ongoing,cyclic, and/or chronic issue that is not that of a sudden, recent,and acute event such as a storm.

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A Few Ongoing Construction Defects

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The opportunities for things to go wrong when constructing abuilding are almost endless. Inevitably something will catch thecontractor or the design team off-guard. What is surprising,however, is the number of issues that are repeated on almost anepidemic scale. A few of those include the following:

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Ventilation. With respect to roofs, properattic ventilation is vital to the performance and longevity of theframing and roof covering. A properly ventilated roof assembly canalso impact cooling costs in warmer portions of the United States.Most building codes (International Code Council, 2006) and industryorganizations (Asphalt Roofing Manufacturers Association) requirethat attics and enclosed rafter spaces shall have cross ventilationequal to one square foot per 150 square feet of ceiling space—orhalf of that, provided the ventilation is split between the upperportion and eaves to promote convection. Proper roof ventilationcan be challenging enough with a conventional attic space. Thefrequent oversight comes into play with vaulted and cathedralceilings. There is no 'attic' to ventilate, but the code stillrequires ventilation of the roof cavity between the rafter and theceiling.

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During an assessment of storm-related damagein the wake of Hurricane Ike, a church with a cathedral ceiling andtongue-and-groove ceiling finish had reportedly sustainedstorm-related distress in the form of discoloration to the interiorceiling finish (see Figure 1).

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After inspection of the roof and exterior wall assembly itquickly became apparent that the property was devoid ofstorm-created openings. The roof was also not equipped with ridgeor soffit vents. Warm humid air becomes trapped within theassembly, gets heated, expands, and escapes between the joints ofthe ceiling finish. Overtime this hot water vapor causesdiscoloration of the finishes.

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Why doesn't the hot humid air vent through the roof assembly?The felt under the shingles and even the shingles themselves becomevapor retarders (Lstiburek, 2001). It is appropriate to have avapor barrier on the warm side of the roof or wall assembly butwith an inadequately ventilated roof, the water vapor will ventwhere it can cause distress to finishes.

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Drainage. Building envelope design can beboiled down into one fairly simple concept: Get the water off theroof (or exterior walls) as quickly and effectively as possible,and there will be fewer issues. The longer water is on the roof,the more likely that imperfections in the flashing, membrane, andpenetrations will become apparent. This category of defect willcoincide almost always with 'it never leaked before the laststorm'. Remember that rain is not very consistent. It may haverained 1/2 inch yesterday but did that 1/2 inch occur in 10 minutesor over the course of 8 hours? If the drains are undersized orclogged, then a seemingly typical rain event can uncover a latentdefect.

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Metal buildings are prime examples of this.The intersection between the metal panel roof and metal panelexterior wall usually has very little in terms of waterproofing. Atbest, it is stuffed with “bird-stop” to keep the critters on thecritter-side of the assembly. Often after heavy rain, apolicyholder reports that a “water fall” was flowing down theinside of one of the exterior walls. What has happened is that thegutters have an exterior edge higher than the top of the exteriorwall panel (Figure 2). When these gutters becomeoverwhelmed—or if the downspouts are clogged—then water flows downthe inside of the exterior wall. How can this be avoided? Buildingsshould be equipped with gutters that spill or have an outer edgelower than the top of the exterior building wall. When the guttersare overwhelmed, water spills to theexterior.    

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Flashing. A material necessary to facilitatethe transition at the interface between a horizontal and verticalsurface, between a penetration and roof or wall surface, and atfenestrations.

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The function, design, and installation of flashing could verywell be the most misunderstood and poorly executed component in thebuilding industry. One classic example (and there are many) is thelack of thru-wall flashing. Its absence is generally either adetailing oversight or hole in the scope of work. Is it the masonwho installs the flashing, or the carpenter who installed thewindow? In a nut shell, there are two basic kinds of exterior wall:the kind that shields us from most of the water but isn't meant tocompletely water-proof (drainage system); and the kind that ismeant to keep 100-percent of the water out of the building (barriersystem).

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Masonry veneers and stucco (exterior plaster and lath system)fall into the drainage system category. The materials used areporous and inherently not completely water proof. These materialsare also brittle, which results in cracks and separation betweenthe components compounding the issue. Because some water getsthrough, they are designed to have a drainage plane behind theproduct. This plane is either a wall cavity or lath that allows fordrainage as well as supporting the plaster. Water penetrates thesystem, hits the weather resistant barrier (building paper) andharmlessly travels via gravity down the wall and safely out theweep holes or weep-screed at the bottom of the wall. Harmless thatis, until it hits a fenestration like a door or window that impedesits journey where it takes the path of least resistance which couldvery well be the interior of the building.

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The solution is to treat any and alldiscontinuities (such as ledger angles, windows, doors, floorslabs, and beams) in the wall cavity as if it were the bottom ofthe wall. This requires thru-wall flashing at each obstruction thatoriginates from under the weather-resistant barrier and extendsunder the masonry or façade to allow water to escape the systemthrough weep holes.

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Figure 3 (to the right) is an example of abrick veneer installed about 25 years ago without thru-wallflashing at the windows. The building owner has had a maintenancenightmare, with chronic water infiltration at the windows. The deadgive-away here is the formation of efflorescence above the windows.This is evidence of a chronic and ongoing condition rather thanthat of a sudden recent event.

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Vapor Barrier on Wrong Side of Wall

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A vapor barrier can be an effective way of mitigating the flowof water vapor that could result in moisture related distress to abuilding. Certain floor covering adhesives, for example, could besensitive to water vapor and in some locations a vapor barrier maybe included under the concrete slab. A vapor barrier under the slabmight also inhibit the formation of efflorescence on tile floorcovering. Water vapor will migrate from warm andhumid to cool and dry. The proper placement of the barrier is onthe warm side to keep the vapor out of the cool, dry place where itcan condensate but the warm side of the wall can change in certainclimates (LaLiberte, 2009).

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A roof membrane, for example, is generally onthe warm side of the roof except in cooler climates in the winter.This is an opportunity for condensation on the bottom of the roofdeck. Insulation on top of the deck mitigates this condition andkeeps the location of dew point above the deck. For a wall thephysics are the same; vapor barriers should be on the warm side ifat all. It is actually kind of a big “if,” and vapor barriersshould only be designed and used if recommended by a licenseddesign professional.

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What if a vapor barrier is installed by accident? What if avapor barrier was not anticipated but installed anyway in the formof vinyl wall paper? In warm, humid climates it is not unusual tosee condensation issues where water vapor is stopped by vinyl wallpaper where it condensates on the cool side of the wall cavity. Anexample of this is evident by the pink spots under the wall paperin Figure 4 above. The pink spots are the resultof smoothing the wall during a remodel with spackle that goes onpink and dries white so one does not need to stick his or herfinger in it when it is time for sanding. When this product getswet, it turns pink again.

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Evidence of OngoingIssues

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Storm-related distress is usually going to be the result ofrecently created openings or other related damage. How can thestorm-created distress be separated from the ongoing constructiondefect conditions? In many cases, it is easier said than donebecause the storm created damage can be on top of a pre-existingcondition. To start, recognize the conditions that take time toform. These include efflorescence, wood rot, corrosion of ferrousmaterials, and evidence of multiple repairs that would beindicative of an ongoing event.

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There are several opportunities for a given building envelope toexperience functional failure. Many of those may be latentconditions waiting for the right combination of events to rear itsugly head. Separating these construction-related deficiencies fromevent-related damage can be sorted out through the recognition ofevidence of chronic and systemic failures of the system.

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