Roof collapses at another commercial building in Anchorage, the 4th in recent weeks

The roof of another commercial building in Anchorage collapsed Friday morning, marking the fourth such incident in the past three weeks. The collapse occurred just days after city officials warned owners of similar buildings to clear snow off roofs after a series of heavy snows this winter.

No one was hurt in Friday’s incident, which involved a flat-roofed warehouse east of the intersection of the Old Seward Highway and East 66th Avenue, at 6616 Rosewood St., officials said.

The Anchorage Fire Department received a report about the collapse at 9:20 a.m., Assistant Chief Alex Boyd said.

Boyd said city building inspectors were on the scene evaluating the building, while the fire department also responded.

The collapse occurred just days after the city issued a warning that the owners of commercial buildings constructed between the mid-1970s and mid-1980s with wood trusses clear their roof of snow as soon as possible.

“It appears to be a truss failure. How exactly it failed, we don’t know,” said Ross Noffsinger, acting building official for the municipality.

[Municipal inspectors advise owners of some older commercial buildings to clear snow from roofs]

The building was constructed in 1983. It still had a J.D.’s Auto Shop sign outside but is being used by an electrical contracting company, Noffsinger said. Workers had been in and out of the building in the morning but were not present when the roof collapsed, and the owner of the company also stored items there, he said.

“The owner said they were like, a day from clearing the snow, he’d been seeing the warnings and they were going to get on it, but they missed it by like, a day,” Noffsinger said.

Large portions of roofs at buildings across the region have collapsed in recent weeks. Southcentral Alaska has seen a series of heavy snowfalls this winter, and snow and ice are piled high on rooftops across the city.

In Anchorage, roofs buckled at a transmission shop off Dowling Road on Sunday, a thrift store near downtown on Saturday and the Turnagain CrossFit gym in South Anchorage three weeks ago, where one person was killed and two others trapped.

Northeast of Anchorage, part of the roof over the Palmer Public Library gave way on Feb. 15. A family inside and several staff members escaped unhurt.

This week, the Anchorage School District closed libraries at five elementary schools over concerns about heavy snow loads on roofs. The district has confirmed those buildings are not made with truss designs the city is concerned about.

Noffsinger said city officials are concerned about commercial buildings. Engineers have said this year’s heavy snow isn’t too heavy for the vast majority of Anchorage houses.

A variety of truss systems have failed in the roof collapses in Anchorage, Noffsinger said.

The wood trusses involved in this latest collapse are not the top-chord hung trusses that were found at the gym and the thrift store, which both had flat roofs. While it’s similar, the truss design used at the Rosewood Street building has weight bearing on the long bottom chord, or horizontal beam of the truss — not the top horizontal beam, Noffsinger said.

Anchorage Mayor Dave Bronson on Friday urged commercial property owners with flat-roofed buildings constructed between the mid-1970s and 1980s to have their buildings reviewed.

“To all commercial property owners with flat roofed buildings built between the mid-1970s and mid-1980s, please have your buildings inspected immediately for their structural integrity and take appropriate action,” he wrote in a post on social media.

The roof at Quality Transmission Service off Dowling Road was pitched, like the roofs on many houses in Anchorage, but it was also made of wooden trusses, the problem in all four commercial building collapses in the city this year.

The city and other engineers are looking at analyzing the trusses in the collapses, Noffsinger said.

In some cases, the metal plates that help hold together the wooden beams of a truss built in the 1970s and 1980s can be too small or not properly placed, potentially allowing truss beams to split and break under the extra weight of snow, Noffsinger said. More modern construction uses larger metal plates to hold the wooden truss beams together, he said.

Engineers have speculated that the collapses occurred in recent weeks because the roofs were sitting under heavy snow loads for months, after a series of heavy snowfalls in December, he said.

The moisture content in the wood could also be problem, Noffsinger said.

The latest collapse makes the city’s warning about clearing snow off certain commercial buildings more urgent, he said.

The Daily News’ Zaz Hollander contributed reporting.