Building envelope assessments for storm-related damage is a normal part of job for the property adjuster and forensic consultant. The assessment of storm-related damage inevitably becomes a question of whether the observed condition pre-dates the storm or is the result of sudden and recent event. In fact, the question may very well be, "Did the observed condition exist during or even before the building was constructed; is the condition the result of a construction or design related defect?"
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 they are sitting there, blocking the view of the sunset. Even a simple building is, in actuality, a somewhat sophisticated "machine." It keeps the wind and rain out, hopefully. A building reflects radiation, insulates from temperature fluctuations, maintains an internal environment, cycles gas, and manages vapor transmissions.
It also transfers gravity-the weight of material, people, equipment, and furniture-and lateral (wind and earthquakes) loads safely to the foundation. This modern machine distributes fresh water and electricity and expels waste. It can detect smoke or unauthorized entry and even call for help. And that is a simple building.
All these things happen when an amazing sequence of events comes together out of seeming (and literal) chaos through the procurement process resulting in a finished building. What can go wrong?
Construction is seldom performed by one entity. Usually there is a general contractor whose job is to "buy-out" (subcontract) the construction of the building. Typically there would be somewhere in the neighborhood of 25 subcontractors and maybe 10 to 15 suppliers, all of which are orchestrated through the general contractor to provide what is, in some cases, an artistic interpretation of the design documents. Each subcontractor has work that will interface with the work of another. The opportunities for overlaps and, worse, holes in the scope of work are many. Multiply that with misinterpretations of and flaws in the design, material defects, and things can go seriously wrong. By the way, none of the opportunities for a construction defect mentioned above include malintent. Defects can happen with honest, well-meaning professionals.
So how does one sort a construction defect from storm-related damage? A claims professional can make this determination in a couple of ways: One is to endeavor to understand the layers of physics associated with a building and identify the root cause of an observed condition based on the current understanding of the physical world. The other is to look for manifestation of a condition 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.
The opportunities for things to go wrong when constructing a building are almost endless. Inevitably something will catch the contractor or the design team off-guard. What is surprising, however, is the number of issues that are repeated on almost an epidemic scale. A few of those include the following:
Ventilation. With respect to roofs, proper attic ventilation is vital to the performance and longevity of the framing and roof covering. A properly ventilated roof assembly can also impact cooling costs in warmer portions of the United States. Most building codes (International Code Council, 2006) and industry organizations (Asphalt Roofing Manufacturers Association) require that attics and enclosed rafter spaces shall have cross ventilation equal to one square foot per 150 square feet of ceiling space-or half of that, provided the ventilation is split between the upper portion and eaves to promote convection. Proper roof ventilation can be challenging enough with a conventional attic space. The frequent oversight comes into play with vaulted and cathedral ceilings. There is no 'attic' to ventilate, but the code still requires ventilation of the roof cavity between the rafter and the ceiling.
During an assessment of storm-related damage in the wake of Hurricane Ike, a church with a cathedral ceiling and tongue-and-groove ceiling finish had reportedly sustained storm-related distress in the form of discoloration to the interior ceiling finish (see Figure 1).
After inspection of the roof and exterior wall assembly it quickly became apparent that the property was devoid of storm-created openings. The roof was also not equipped with ridge or soffit vents. Warm humid air becomes trapped within the assembly, gets heated, expands, and escapes between the joints of the ceiling finish. Overtime this hot water vapor causes discoloration of the finishes.
Why doesn't the hot humid air vent through the roof assembly? The felt under the shingles and even the shingles themselves become vapor retarders (Lstiburek, 2001). It is appropriate to have a vapor barrier on the warm side of the roof or wall assembly but with an inadequately ventilated roof, the water vapor will vent where it can cause distress to finishes.
Drainage. Building envelope design can be boiled down into one fairly simple concept: Get the water off the roof (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, and penetrations will become apparent. This category of defect will coincide almost always with 'it never leaked before the last storm'. Remember that rain is not very consistent. It may have rained 1/2 inch yesterday but did that 1/2 inch occur in 10 minutes or over the course of 8 hours? If the drains are undersized or clogged, then a seemingly typical rain event can uncover a latent defect.
Metal buildings are prime examples of this. The intersection between the metal panel roof and metal panel exterior wall usually has very little in terms of waterproofing. At best, it is stuffed with "bird-stop" to keep the critters on the critter-side of the assembly. Often after heavy rain, a policyholder reports that a "water fall" was flowing down the inside of one of the exterior walls. What has happened is that the gutters have an exterior edge higher than the top of the exterior wall panel (Figure 2). When these gutters become overwhelmed-or if the downspouts are clogged-then water flows down the inside of the exterior wall. How can this be avoided? Buildings should be equipped with gutters that spill or have an outer edge lower than the top of the exterior building wall. When the gutters are overwhelmed, water spills to the exterior.
Flashing. A material necessary to facilitate the transition at the interface between a horizontal and vertical surface, between a penetration and roof or wall surface, and at fenestrations.
The function, design, and installation of flashing could very well be the most misunderstood and poorly executed component in the building industry. One classic example (and there are many) is the lack of thru-wall flashing. Its absence is generally either a detailing oversight or hole in the scope of work. Is it the mason who installs the flashing, or the carpenter who installed the window? 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 to completely water-proof (drainage system); and the kind that is meant to keep 100-percent of the water out of the building (barrier system).
Masonry veneers and stucco (exterior plaster and lath system) fall into the drainage system category. The materials used are porous and inherently not completely water proof. These materials are also brittle, which results in cracks and separation between the components compounding the issue. Because some water gets through, they are designed to have a drainage plane behind the product. This plane is either a wall cavity or lath that allows for drainage as well as supporting the plaster. Water penetrates the system, hits the weather resistant barrier (building paper) and harmlessly travels via gravity down the wall and safely out the weep holes or weep-screed at the bottom of the wall. Harmless that is, until it hits a fenestration like a door or window that impedes its journey where it takes the path of least resistance which could very well be the interior of the building.
The solution is to treat any and all discontinuities (such as ledger angles, windows, doors, floor slabs, and beams) in the wall cavity as if it were the bottom of the wall. This requires thru-wall flashing at each obstruction that originates from under the weather-resistant barrier and extends under the masonry or façade to allow water to escape the system through weep holes.
Figure 3 (to the right) is an example of a brick veneer installed about 25 years ago without thru-wall flashing at the windows. The building owner has had a maintenance nightmare, with chronic water infiltration at the windows. The dead give-away here is the formation of efflorescence above the windows. This is evidence of a chronic and ongoing condition rather than that of a sudden recent event.
A vapor barrier can be an effective way of mitigating the flow of water vapor that could result in moisture related distress to a building. Certain floor covering adhesives, for example, could be sensitive to water vapor and in some locations a vapor barrier may be included under the concrete slab. A vapor barrier under the slab might also inhibit the formation of efflorescence on tile floor covering.
Water vapor will migrate from warm and humid to cool and dry. The proper placement of the barrier is on the warm side to keep the vapor out of the cool, dry place where it can condensate but the warm side of the wall can change in certain climates (LaLiberte, 2009).
A roof membrane, for example, is generally on the warm side of the roof except in cooler climates in the winter. This is an opportunity for condensation on the bottom of the roof deck. Insulation on top of the deck mitigates this condition and keeps the location of dew point above the deck. For a wall the physics are the same; vapor barriers should be on the warm side if at all. It is actually kind of a big "if," and vapor barriers should only be designed and used if recommended by a licensed design professional.
What if a vapor barrier is installed by accident? What if a vapor barrier was not anticipated but installed anyway in the form of vinyl wall paper? In warm, humid climates it is not unusual to see condensation issues where water vapor is stopped by vinyl wall paper where it condensates on the cool side of the wall cavity. An example of this is evident by the pink spots under the wall paper in Figure 4 above. The pink spots are the result of smoothing the wall during a remodel with spackle that goes on pink and dries white so one does not need to stick his or her finger in it when it is time for sanding. When this product gets wet, it turns pink again.
Storm-related distress is usually going to be the result of recently created openings or other related damage. How can the storm-created distress be separated from the ongoing construction defect conditions? In many cases, it is easier said than done because the storm created damage can be on top of a pre-existing condition. To start, recognize the conditions that take time to form. These include efflorescence, wood rot, corrosion of ferrous materials, and evidence of multiple repairs that would be indicative of an ongoing event.
There are several opportunities for a given building envelope to experience functional failure. Many of those may be latent conditions waiting for the right combination of events to rear its ugly head. Separating these construction-related deficiencies from event-related damage can be sorted out through the recognition of evidence of chronic and systemic failures of the system.
EFI Global is a full-service Engineering, Fire Investigation, Environmental, Health and Safety, and specialty consulting firm. Over the last four decades, they have grown from a boutique firm to become a recognized leader in engineering failure analysis, origin and cause investigations, and environmental consulting. This expertise coupled with the extensive coverage of our 27 national offices, more than 400 professionals, and global work abroad capability allows EFI Global to deliver timely responses that consistently meets their clients' expectations.
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