Waters in the storm…into the house they’re borne
Chapter 1: Waters from the Storm
The first sign of trouble at the condominium building appeared in late October 2021. Residents in the third and fourth floor units noticed water leaking from their living room ceilings. More leaks appeared in the common areas below a fifth-floor balcony.
The condo building was relatively new, finished in 2018, and there had been no reports of previous leaks into the building. The property manager had a contractor come out to investigate and repair the damage. As the contractor began to remove damaged finishes, more moisture was discovered in the walls and ceilings. Repairs were made, but several months later, in December, more leaks appeared.
A few miles away at a large single-family home, a family of four had recently returned from an extended trip out of the country. It was just before Christmas and, during a storm, the family noticed water dripping from the ceilings in the living room and kitchen. Additional leaks would be discovered in the guest room, recreation room, and garage. The family reported no prior leaks in the home. The custom two-story home was built in 1982 and had stone walls, Mediterranean-inspired architectural elements, arched windows, curved ceilings, hardwood floors, and decorative paintings over Venetian plaster walls.
Across the Bay in an iconic three-story Victorian home, the homeowners noticed a sudden water leak in their garage after a storm in late December. The water flowed openly across their garage floor and out towards the street. When a reconstruction contractor came to the home to repair it, extensive rot damage was found behind the finished walls and ceiling. It was clear that water had been getting into the walls for a long time, but had only recently leaked into the garage.
Chapter 2: A Closer Look
Water leaks had appeared at all three properties around the same time—during the rainstorms that blew through the Bay Area in late 2021. But each home was so different—the first, a relatively new condo building; the second, a large 40-year-old home in a suburban setting; the third, an historic Victorian home built in 1900. All three homes had damages that required extensive repairs.
The question to be answered: Were the two big storms in October and December the cause of damage to all three properties? Or were there pre-existing conditions that the storms suddenly exposed? Degenkolb was hired to find out, and sent out forensic engineer Steve Moore.
At the condo building, repairs were already underway after the storms. The contractor had removed some of the wall finishes, covered up the fifth-floor balcony with temporary plastic tarps, and sealed open exterior joints with caulk and backer rod. There were no obvious openings where the water could have entered, but the leaks continued during subsequent storms. Inside the walls, Degenkolb’s Steve Moore probed the stained wall framing where he found solid and firm wood and lightly rusted fasteners with no evidence of long-term moisture exposure. With the plastic installed over the balcony and all exterior joints sealed, how did water continue to leak into the units below?
Down the road at the large single-family home, the evidence told a different story. French doors in the bedrooms and playrooms open to balconies and walkways on the second floor. Floor drains were supposed to have captured rainwater before it entered the residence. We noticed, however, that the wood at the threshold of each door was warped, separated, and split. We also noticed that the floor drains were filled with leaves and other debris. Plants had started to grow up through the drain covers, effectively blocking them. But did this translate to water in the living room ceiling? If so, how?
Across the Bay at the 120-year-old Victorian home, the challenge was following the evidence of water damage to its source. Inside the garage, behind the removed wall finishes, the damage was evident— stained and rotted framing members in the corner around a rainwater drainage pipe. We followed the damage to a second-floor balcony above the garage. Upon examining the balcony floor above, we noticed intact conditions with no obvious voids or cracks in the floor tile around the roof drainpipe. How was the water getting through the balcony floor?
At each residence, it initially seemed the storms were responsible for the damage, since there hadn’t been leaks before or significant rainfall due to the ongoing California drought. But by peeling back the layers and examining the evidence, a few clues were revealed that pointed to other reasons.
Chapter 3: The Culprits
The exterior wall finishes on the condominium are comprised of stucco, which is designed to allow rainwater to penetrate through the cement plaster and then drain out the bottom. On a balcony, the bottom of the stucco drains onto flashing at the wall-to-balcony intersection. The flashing directs water to a drain system in the balcony floor assembly. The cause of the water intrusion was missing or improperly installed flashing at the wall-to-balcony intersection, likely the result of an original construction defect. The condition hadn’t been noticed earlier because not enough rain had fallen since the condo had been built to become a problem.
At the large single-family home, we determined that when it rained sufficiently, water from the balcony overwhelmed the blocked drain, pooled on the balcony, and then overflowed the thresholds into the floor assemblies. We observed that the wood at the door thresholds was warped and there were deep cracks in the grain. When wood is damaged by water, the cycle of wetting and drying become exacerbated each time. Cracks in the wood become deeper, the cellulose breaks down, and it becomes easier for water to penetrate the next time it rains, causing further damage. It was clear that the wood had become wetted and dried several times before the storms in late 2021. The cause of the water intrusion was a lack of maintenance of the exterior drainage, which resulted in significant water penetration during the large storms of 2021.
At the Victorian, it was clear that the moisture damage to the framing had been occurring for many years, but the water had not previously flowed into the garage. Upon closer examination of the balcony, we identified a failed joint at the guardrail intersection with the exterior wall. The failed joint was the result of dried and cracked sealants and paint, which allowed rainwater to penetrate the wall cavity. The failed joint had been allowing water intrusion for many years, but it was not until the excessive flow in December 2021 that the long-term deterioration was revealed.
Each building had first noticed water intrusion during significant storm events in late 2021. Without any history of prior leaks, it was initially believed that the storms had caused the leaks. But after careful forensic assessments of each location, the physical evidence revealed the actual causes: different pre-existing issues that had manifested well before the rains fell—an initial defect in construction, a lack of routine maintenance, and dried and cracked sealants and paints, respectively. These three examples of sudden rainwater intrusion illustrate the importance of taking the time to closely examine and follow the evidence path and to not just blame the damage on the water in the storm.
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To speak with a Forensic Engineer or to schedule an investigation, contact Steve Moore at firstname.lastname@example.org.
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Reflections on Katrina: Supporting Others in Difficult Times
A pair of children’s shoes hang from a telephone wire. Broken picture frames filled with water-damaged photos of major life events litter the ground. Gemstones that used to hang from a chandelier that had been in the family for four generations glint feebly from underneath piles of debris. Katrina’s storm clouds had dissipated three months earlier, but the devastation remained scattered across the communities and land that had the misfortune of being in her path.
Degenkolb* staff was on-site to conduct an investigation on a homeowner’s claim. This time, the homeowner met the engineers and their Claims Coordinator at the site. Mounds of rubble lay in a heap on top of the slab where his house used to stand. As the engineers did their work, the homeowner sifted through what was left. Much of it was unrecognizable — items damaged during the storm had then sat outside, exposed to sun, humidity, and more rain for weeks and months. Many sentimental items were now beyond salvageable. The homeowner was looking for anything that had even remotely survived.
Lisa Esquivel was the team’s tireless Claims Coordinator. When Degenkolb’s investigative engineering team started getting calls to go down to Mississippi and investigate the cause of loss — a nuanced determination between the wind from the storm or flooding from surge waters — Lisa was the one who found a furnished apartment to stay in. She and the IT manager were the ones to go out and buy the computers and tech equipment needed to operate a field office (this was well before remote work setups were common). Lisa coordinated the schedules, set up the files, made sure there was food in the fridge, and towels and bedsheets were cleaned between multi-week shifts of engineers. When the engineers went to the sites, she was the one who interacted with the homeowners. She offered a sympathetic ear when they told their stories – what they went through when they left, or the reasons for why they didn’t. She heard the way they agonized in uncertainty when they didn’t know what had happened to their home or whether their insurance carrier would cover their loss.
In the evenings, while the engineers discussed the types of damage they’d seen and the indicators of cause of loss, Lisa thought about what she’d seen, sometimes overwhelmed to tears with empathy for the kind, generous, and welcoming people who’d lost almost everything. These people’s lives — nearly everything they owned — lay scattered across neighborhoods and towns, some of it lost forever. During catastrophes like a hurricane or a wildfire, the advice is that things can be replaced but people cannot; it’s meant to encourage folks to prioritize their safety first and foremost. This saying is certainly true; a human life cannot be replaced. But losing everything around one’s life—photos, children’s’ drawings, gifts from friends and family, hobbies and collections—is still a significant loss that takes an emotional toll.
The home where the team had been that day was once used as a filming location for a major motion picture in the late ‘90s. At that time, the homeowner hadn’t accepted payment for the use of his home for filming. At the end of shooting, the crew presented him with a unique gift: A framed dollar bill signed by the crew and stars of the film, which included several major Hollywood actors. While sifting through the debris, he found the frame with the signed dollar bill intact. Excitedly, he showed it to Lisa, who shared in the man’s joy at finding at least one of his irreplaceable items. It was a small, but impactful, step forward in a long journey to recover and rebuild.
Sixteen years later (to the day), Hurricane Ida struck the Gulf Coast once more. This time the levies held, but the winds and water appear to have been no less devastating in 2021 than they were in 2005. For Ida, the post-catastrophe work hasn’t yet begun—it will be weeks to months before adjusters and engineers are able to safely visit sites and assess damage. That tireless Claims Coordinator, Lisa Esquivel – now the Forensics Operations Manager for Degenkolb Engineers —is reflecting on the valuable lessons we learned from Katrina, preparing herself and her colleagues for the journeys they may take, and hoping for small but impactful steps forward by those who were affected by Ida.
*Degenkolb Engineers acquired Barrish Pelham Consulting Engineers in 2018. Staff involved in the Hurricane Katrina recovery story were at the time employed by Barrish Pelham and are now employees of Degenkolb Engineers.
To learn more about Lisa’s journey and to help gain focus on investigative engineering for Ida, please reach out to email@example.com.
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How I Found Myself Upside Down in A Dumpster
A carrier adjuster contacted Degenkolb because they needed a forensic engineer to determine the cause of a failed fire sprinkler that had flooded an office area in a local commercial building. Just after 11:00 pm on the date of loss, the fire department received a notification that the sprinkler system for the building had been activated. After determining there was no fire, the fire department temporarily shut-off the fire sprinkler system. It was reported that a single fire sprinkler had failed and damaged the office area below it.
When I visited the site, I saw that all the cubicle furniture and carpet flooring had been removed from the roughly 50-foot by 50-foot square room. Additionally, the four acoustic tiles around the failed sprinkler were missing. The building manager told me that the four panels had been found on the ground the morning after the loss and were thrown in a dumpster at the back of the building.
I documented the existing conditions of the room and took a very close look at the failed sprinkler head. The mercury link for the fixture had been replaced and the fire protection system for the building had been reset and was properly functioning. I noted no evidence of distress on the surfaces of the fixture or long-term corrosion on the pipes and/or fittings. The pipe support hardware, the roof framing, and the surrounding building systems appeared intact and properly functioning. So, how did this single fire sprinkler in the middle of a conditioned office area fail? Where was my “smoking gun”?
I decided to check the dumpster at the back of the building. I needed to see the ceiling panels around the failed sprinkler head. I swallowed my pride, reflected on my desire to find the real cause of this loss, and did some dumpster diving, which is ultimately how I ended up upside down inside the dumpster. Thankfully, my efforts paid off! Under plastic sheeting and some carpet rolls, I found three of the four ceiling panels. They were tattered and damaged, but I was able to reassemble them on the ground next to the dumpster. Extending across two of the three panels, adjacent to the location of the fire sprinkler, were a series of black crescent-shaped shallow grooves in the acoustical panel surface. How and when did these Nike swoosh shaped markings get on the ceiling panels?
I returned inside where I met with the manager in his office and asked more questions about the building. Inside his office, the gadget-loving engineer in me immediately noticed a large remote-controlled helicopter sitting on the floor. The manager explained that several employees would fly the helicopter in the parking lot during lunch and, when not in use, it was normally stored in the damaged office area. The helicopter and its controls were found on the floor the morning after the sprinkler failed. I took a closer look at the helicopter and noted a white residue along the leading edges of the rotor blades.
Following this lead, I asked the manager if any employees were in the building when the fire sprinkler failed and he said no; he had been the last to leave the building earlier that evening. I then asked him if there is a cleaning service for the building and immediately his eyes popped wide open—something had clearly clicked for him. The manager accessed the security system for the building and found that around 10:30 pm on the date of loss, someone had accessed the building. The manager contacted the cleaning service company and they admitted that the employees in the office that night had been playing with the helicopter inside the office area when it flew out of their control, impacted the ceiling, and hit the fire sprinkler, which then triggered the fire suppression system.
This investigation shows that forensic engineering is about more than a single discipline; it’s about following clues, interpreting their meaning, and testing hypotheses. Whether the cause is obvious—like a tree has fallen through a roof or a car has gone through a wall—or harder to determine—like what’s causing mold growth inside a window—the first step in determining the cause is collecting evidence and making observations. With a little extra “diving” effort, asking pointed questions, and following the evidence, a forensic engineer can successfully determine the cause and origin of damage, even when it’s unexpected! This was one of those times.
Steve Moore, P.E., CASp
Read more of Steve’s articles here.
When Swimming Pools Pop
When summertime brings warm sun and hot weather, many homeowners try to beat the heat by taking a dip in a cool swimming pool. Some are lucky enough to have their own backyard pool to use at their leisure. But being a pool owner is not always like floating on an inflatable lounge chair, coconut drink in hand. Routine maintenance, cleaning, and proper equipment are crucial to keeping a pool in good working order, and when those things don’t happen or are ill-timed, serious and potentially permanent damage can occur to the large financial investment that is a swimming pool.
One type of property damage claim that Degenkolb’s Forensic Engineers see regarding residential pools is when the in-ground portion of the pool lifts–or pops up–out of the ground. Not only has the shell of the pool experienced irreparable damage, but the surrounding pool deck, the underground plumbing, and adjacent structures are also affected. But why does this happen?
In-ground pool shells are typically constructed of gunite, a material similar to concrete but applied via a spray gun directly onto the undisturbed soils of a pool excavation. Six inches of gunite creates the pool shell, and advantages to using it are its structural strength and variations in surface shape. Homeowners and designers can create whatever shape of pool they want, whether that’s a rectangle or more free-form curving shapes, like tunnels that lead into a home and swim up bars! Once the gunite dries and a plaster finish coat is applied, a shell is formed that holds the pool water.
The weight of the pool varies dramatically when empty or full, and this is where the real structural problems start to arise. In areas like California, the moisture content of the soils and the water table elevation vary from season to season, with more water in the ground during the winter months. If the local water table elevation rises to the depth of the pool due to a wet winter season, the buoyant force from displaced water tries to lift the shell up out of the ground. Fortunately, the weight of the gunite shell, the surrounding deck, and the water in the pool counteract these forces and keep the structure in the ground. But what happens when the water level of the pool rapidly drops or the water is removed from the pool for maintenance reasons?
Without the weight of the water in the pool, an elevated water table could produce large enough buoyant forces to lift the shell up out of the ground. Everyone has seen the extremely large cargo container ships and wondered how they stay afloat. Well, it’s all about Archimedes’ Principle, which states the buoyant force on a submerged object is equal to the weight of the volume of displaced water. Unfortunately, this is the moment when irreparable damage to the pool can occur. Not only are the plumbing pipes, electrical conduit, and surrounding deck damaged, but the soils under the gunite shell consolidate and fill the void—the shell cannot drop back down to its original elevation when the ground water table drops again.
But what if my empty pool pops out of the ground in the summer? Or what if my completely full pool pops out of the ground? Those types of questions require digging deeper and investigating the true cause of the elevated water table. Sub-grade plumbing leaks, crack formation in the plaster finish coat and gunite shell, defective equipment, improper installation methods, bond beam and deck coping separation, and surrounding topography are some examples of the true cause behind a popped swimming pool and can be very difficult to identify without proper experience and expertise.
So where would a pool owner or any interested party go to find out information about the ground water table in their neighborhood? Well, a couple of options would be to consult with a Contractor or Forensic Engineer specializing in swimming pool construction and installation. Another option would be to visit the California Department of Water Resources website and research historical data for wells.
If you are a pool owner and want to protect that fun and wonderful investment in your backyard try to keep an image in the back of your mind of ancient Archimedes lounging in his bathtub exclaiming that single word of discovery and enlightenment, “Eureka!”.
Read more of Steve Moore’s blog articles here.
Aqua Workz Commercial Roof Collapse
When Mother Nature Forecloses on a Property
Several years ago, I investigated reported storm-related damages to a single-family residential structure near North Cove, Washington, between Tokeland and Grayland on the coast of the Pacific Ocean. It was reported that wind and erosion had caused near-complete destruction of the house. I was no stranger to storm-damaged structures, but I was not prepared for what I found.
I tried to drive to the location using my spiffy new GPS navigation system but kept encountering road closed and detour signs that appeared to be recently installed. I pulled over and got out to look. About 30 feet beyond a temporary folding traffic barricade sign, the asphalt pavement sheared off abruptly at the edge of the coastal bluff, about 20 feet above the beach below. I looked up and down the coast and saw numerous streets that terminated abruptly at the near vertical scarp of the coastal bluff. I could not help but picture the cover of Shel Silverstein’s classic collection, Where the Sidewalk Ends.
I returned to the car and, despite the lack of street signs and posted addresses, managed to find the house based on some old photographs and a rough description from the owner. I was astounded at what I found. The soils supporting the foundation of this house had washed out to sea and the west half of the house was resting on the beach, about 15 feet below the east half, which remained up on the bluff. The sandy soils of the bluffs were quite unstable, so I maintained a respectful distance as we documented the extent of the damages observed.
The area was a ghost town so there were no neighbors around to interview; I made a short drive up the coast to the Grayland Beach State Park, where Park Rangers at the park office informed me that particular section of beach had been nicknamed “Washaway Beach” and is one of the fastest-eroding coastlines in the world. It seems that every year the Pacific Ocean claims an average of 100 feet of coastline in this area as measured perpendicular to the shore. Thus far, the coastal erosion has claimed more than 50 houses, a lighthouse, a schoolhouse, and even a Coast Guard station.
The cause of the dramatic coastal erosion in North Cove is the erosion of the sand spit that once protected North Cove. Historic dredging and construction of hydroelectric dam projects on the Columbia River have altered the location of the drainage channel and created a condition in which southerly storm waves break close to the shore, greatly eroding the beach.
Solutions considered to help protect the coastal communities in this region have trended away from the use of larger rip rap and other rigid armoring techniques in favor of an approach called “dynamic revetment,” in which a band of cobbles (3- to 10-inch diameter stones) is utilized at the base of the bluffs to absorb wave energy. The results of utilizing cobbles for dynamic revetment have been measurable and impressive, slowing erosion to rates as little as 30 feet per year in 2017 and zero in the 2018 – 2019 storm season.
While it was too late for the dwelling I was sent to investigate and for most of the property on which it was constructed, dynamic revetment is proving itself to be an effective mechanism for delaying the effects of coastal erosion in this region.
Written by Scott Thomas, April 23, 2021
Water Falling on Fish
It was early Spring when I pulled up to a retail building where I’d been sent to investigate a collapsed roof. From the street, the only signs of something fishy was a slightly bowed parapet wall, which was leaning inwards. Once inside, the scope of damage was readily apparent—a large section of the central roof had completely collapsed. Amongst the wreckage of roof framing, ceiling panels, and wet insulation were damaged fish aquariums and their related accessories. The unmistakable scent of fish—earthy and musty, like fresh-tilled soil—lightly perfumed the air. Thankfully, most, if not all, of the aquariums’ finned inhabitants had been saved by the owners of this “fishstablishment.” But the pressing and immediate issue was the enormous hole in the roof—what had caused it?
As I combed through the debris, clues began to emerge. Ceiling tiles showed evidence of water staining; the metal ceiling grid was corroded with dark red rust, and the batt insulation was darkly stained and matted. Wood roof truss chords were darkly stained and covered with white and yellow mold. I took out my knife and inserted it into several of the mold-laden truss chords. Metal pins in the trusses were heavily corroded and the plywood roof sheathing was decayed and deteriorated. I also noticed a curious plastic sheeting, not dissimilar from radiant barrier material, had been stapled to the bottom truss chords.
I ventured into an area of the building where the roof had not collapsed and was able to observe the roof conditions. Even here, with some distance from the collapsed roof, there were signs of moisture exposure.
In search of additional clues, I ventured onto the roof. Like many commercial buildings, it was a shallow sloped roof with scuppers in the front parapet walls. Most of the roof appeared to be in good condition, with the exception of the collapsed area. Interestingly, I noted the collapsed had been patched over with additional roofing materials. Using Google Earth, I was able to determine that the patch had been recently installed—within the last several months—as it wasn’t present in the Google Earth image. The owner reported that during the last two years, multiple roof leaks had been repaired by a contractor. With my head swimming with information and seemingly related clues, i was primed to solve the puzzle, but I was floundering a bit for an answer.
The damage to the interior components was more severe and long-term than what one might expect from a roof collapse due to ponding. There also hadn’t been any significant rainstorms in the area for several weeks. As such, it was a seemingly a “blue sky collapse.” I reflect on the reported roof leaks and patching–perhaps a red herring? A hypothesis emerged—perhaps the roof wasn’t leaking from the outside; perhaps the water was coming from inside the building.
Among the roof debris and damaged aquariums stood a few that were spared; these aquariums had no covers, allowing water to easily evaporate from them. It all added up—numerous open aquariums had created warm, moist air conditions throughout the interior of the building. Water vapor migrated up through the ceiling, condensing on the underside of the cold roof deck. After wetting the wood, water droplets then fell back down onto the plastic sheeting and suspended ceiling surfaces. Not only were the aquariums producing water vapor, but as the daytime temperatures increased, the water trapped in the ceiling would again vaporize and rise up to the underside of the roof deck where it would later condense once again. There were multiple cycles of daily water vaporization and condensation occurring within the building, even during the spring and summer months!
The scale of the problem was large and permeated to all parts of the building. The worst of the damage, however, wasn’t readily visible to the occupants, as it was hidden behind layers of acoustic ceiling and plastic sheeting. This proved to be crucial in terms of insurance coverage and was an important aspect of our cause and origin report.
As I left the site, I didn’t want to waste what was left of a nice Spring day—carp-e diem! I thought, as I drove off into the sunset.