New information released by the state shows how the Library Gardens balcony builders made deadly departures from the design specifications.

A downtown Berkeley balcony that collapsed in 2015, killing six young people, was built using unstable and water-absorbent materials rather than sturdier supplies described in construction plans, according to documents released by the California Contractors State Licensing Board this week.

The 145-page packet sheds light on the state’s decision to revoke the license of Segue Construction, the contractor responsible for the complex known initially as Library Gardens. (It has since been renamed.) The information in the documents supports an earlier determination by the state that Segue and its sub-contractors neglected critical elements of the design drawings and failed to make the balconies waterproof.

Read complete balcony collapse coverage on Berkeleyside

An expert report included in the packet found serious gaps between design specifications and the eventual construction. Architect and contractor Robert Perry, of Perry Consulting Group, examined project documents and remnants of the balcony from the 2020 Kittredge St. site. The pieces of the collapsed balcony were stored in several locations, including a city of Berkeley public works yard and the Santa Rita Jail.

The report says “dry rot damage … along the top of the cantilever balcony deck joists,” or supports, ultimately caused the balcony to break off from the apartment building. The weight of the 13 students on the balcony at the time was not a factor, he said, noting that the weight was “well within the design limits of the balcony.”

The dry rot found on the balcony pieces shows the structure was saturated with moisture, the report says. A city of Berkeley inspection immediately after the tragedy similarly found that the balcony supports were “severely dry rotted.” That is not surprising, Perry told Berkeleyside, because the builders used oriented strand board, a much more absorbent alternative to the plywood specified in the design.

“Most of us in the design professions avoid [the material] like the plague,” Perry said Friday. When the material is exposed to moisture for a long time, “you can just grab a handful and it turns into sawdust,” he said. Shortly after the collapse, Berkeley prohibited the use of the material on such structures.

Although the balcony was eventually waterproofed, the design called for a protective covering to be used during construction. In his report, Perry notes that, between October 2005 and August 2006, when it rained almost 39 inches in Berkeley, there is “no mention of framing protection from inclement weather” in construction logs. Around the same time, mold was discovered inside units in the building.

Additionally, the balcony supports were not pressure-treated as directed in the design drawings. “That would have helped,” Perry said.

In lawsuits against Segue Construction and many of its sub-contractors, families of the victims in the balcony collapse say the balcony would get so moist that mushrooms grew out of it. In May, the families reached a partial settlement with the contractors.

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Segue must wait five years to reapply for a license to operate, per an April settlement with the state.

The fifth-floor balcony fell off the downtown Berkeley building in June 2015 during a 21st birthday party for an Irish woman. She had come to Berkeley for the summer on a temporary work visa along with many of her peers.

The young people killed in the collapse were Ashley Donohoe, 22, from Rohnert Park; and Olivia Burke, Eimear Walsh, Eoghan Culligan, Nick Schuster and Lorcán Miller, all 21 years old and from Ireland. Seven other people standing on the balcony survived with injuries.

Although mourners continue to leave photos and flowers memorializing the victims at the former Library Gardens site, the building itself shows little trace of the tragedy. It has been renovated and rebranded as K Street Flats.