Report: Davenport building collapse had two ‘root causes’

DAVENPORT — Removed brick and inadequate support structures caused the west wall at a downtown Davenport building to collapse in May, an investigative report released Thursday concluded.

The report is dated Aug. 15, and was completed by two city-hired investigative engineering companies on the causes and origins of the partial collapse of the six-story building at 324 Main St. on May 28. The collapse resulted in three deaths, one person losing their leg, and many more homes and belongings lost.

The 113-page report determined that removing layers of brick during repair work in the three days before the collapse "severely compromised the western bearing wall" and that "the temporary shoring that had been installed was grossly inadequate."

"Had a proper shoring and construction phasing plan been implemented during these repairs, the building would not have partially collapsed on May 28, 2023," the report's executive summary stated.

The city hired two companies — White Birch Group, LLC, and SOCOTEC Engineering, Inc. — to investigate the cause of the collapse in the days after it happened. The report is likely to inform lawsuits and an investigation by the Iowa Division of Criminal Investigation.

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“Since the day of the partial collapse at 324 Main Street, we have been laser-focused on identifying the causes of this tragic incident,” Mayor Mike Matson said in a prepared statement. “We engaged the services of the consultants who responded to the Surfside condominiums collapse in 2021, and we promised the public we would share their findings. Today, we are following through on that promise. Our hearts and thoughts remain with the families of Ryan, Branden, and Daniel and their loved ones, friends, and neighbors.”

City officials, facing sharp questions and criticism from residents attending public comment at council meetings, have said they plan to look to the report for answers, including for policy direction.

The investigation, however, is limited to the building design, construction, and repair-related causation of the partial building collapse, investigators wrote in the report. City policy is beyond its scope.

Root causes determined

The report cited two "root causes" of the collapse at 324 Main St.:

It cites specific problems with the design and efforts to stabilize and prop up the western wall during repairs, called shoring.

The report states that the shoring installation, which it says was "severely lacking," engaged only limited portions of exterior brick, the spacing of the shoring "was inadequate given the extent of the brick removal," the pieces of shoring were "severely undersized," and the shoring wasn't properly restrained where it was touching the wall and the pavement.

The report also lists seven "proximate causes" of the collapse, including improper understanding of the building construction and construction documents, inadequate oversight of repairs, inadequate repair techniques, inherent weakness of the west wall, and inadequate maintenance.

Pictures in the report from May 26, two days before the collapse show workers removing sections of brick wall. Another taken May 27 show more brick was removed. Removing the brick reduced the masonry wall from five wythes thick down to two to three wythes in thickness. No more work was done after May 27, according to security footage reviewed by investigators.

“Overall, the analysis indicates that removing the outer wythes of brick without providing adequate shoring compromised the structural integrity of the wall sufficiently to precipitate collapse,” the report stated.

Engineers, contractors underestimate damage to wall

Because engineers and masonry contractors misidentified the west wall as a non-structural system, "they underestimated the significance of the observable signs of distress in the wall, delayed necessary repair work, designed and installed a weaker replacement system, and removed significant portions of the wall without first installing adequate temporary shoring," the report stated.

Select Structural was the engineering firm hired by building owner Andrew Wold to assess the building and inform repairs. Bi-State Masonry was company Wold contracted to repair the brick masonry.

Wold had approached another masonry company owner to request a bid, the Quad-City Times/Dispatch-Argus previously reported, but rejected it because it was too high.

R.A. Masonry owner Ryan Shaffer told a reporter at the time that Wold "wanted to cut the cost by cutting out the shoring and supporting of the building."

Wold has sued Select Structural for failing to identify risk of collapse or danger to the building's occupants.

When reached by phone, representatives for Select Structural Engineering and Bi-State Masonry declined to comment.

Wold did not respond to a request for comment.

The investigative report minces no words in stating Select Structural's duties. The report says photos between 2020 and 2023 show wall damage and movement that "should have raised significant concerns."

The report references pictures of diagonal cracks in both the exterior and interior masonry and displaced window frames that indicated wall movement and masonry distress.

Inadequate construction documents result in incomplete repairs

The report states that construction documents for repair work between 2020 and 2023 did "not provide adequate details and specifications for a contractor to implement the repair work necessary" at 324 Main St.

The report also says that the "lack of documentation limited the city inspectors' ability to easily verify that the work being performed was consistent with the engineer's intent."

Too little oversight of repairs

The report states that "deficiencies with the design and implementation of repairs noted herein were exacerbated by the lack of on-site presence by a qualified Design Professional during the repair work. This lack of professional oversight allowed the work by the most recent repair contractor to proceed in an unsafe, incomplete, and improper manner."

Emails and reports showed that David Valliere, the engineer with Select Structural, visited the site in early February, Feb. 23, and in late May.

West wall brick replacement 'substantially weaker'

The original brick wall was five wythes thick, the report stated. A wythe is a vertical section of brick that is one unit thick. The engineers and masonry repair contractors replaced the bearing wall "with a substantially weaker non-composite cavity wall system."

Improperly repaired brick increased weakness of wall

The report stated that "improperly repaired brick masonry wall sections were poorly integrated with the original construction and increased the weakness of the west elevation wall."

Infrequent maintenance also led to weaker walls

The report concluded that the building exhibited signs of "improper and inadequate exterior envelope maintenance, resulting in excessive water infiltration."

"Improperly maintained composite clay brick masonry walls will degrade over time due to water infiltration and the effects thereof, resulting in a structurally weakened wall system."

Citing photos of the pre-collapsed building, the report concluded "it is apparent that the building ownership/management did not adequately address exterior (and other) maintenance requirements, thereby resulting in the compromised integrity of the west elevation wall."