Spenard Builders Supply dispatch center destroyed in Anchorage roof collapse

A large commercial building in Spenard was destroyed in a roof collapse late Wednesday, a month after municipal officials warned of potentially disastrous loads from what’s already a record snow season.

The collapse took place just before 11 p.m. at the Spenard Builders Supply dispatch center off West 46th Avenue, according to Anchorage Fire Department spokesman and deputy chief Alex Boyd. A fire alarm notification was the first alert, followed by numerous calls reporting the collapse, which sent debris flying into surrounding streets but caused no additional damage, Boyd said.

No one was inside the structure at the time, he said. The dispatch center was housed in what was once the SBS truss plant located at the northeast corner of West 46th and Taft Street, a couple blocks from the Tudor Road-Minnesota Drive intersection.

The collapse marks at least the third time in less than three years that a roof on an SBS building has buckled.

Representatives of Spenard Builders Supply said Thursday that they are taking steps to determine the cause of the latest collapse.

The business is taking actions to implement preventive measures to avoid future roof problems, according to an email from Carter Reves, a general manager with Spenard Builders in Anchorage.

”Spenard Builders Supply, and its parent company Builders FirstSource, are working to minimize any disruption to operations and services to our customers, and we currently do not expect any significant disruptions with our retail center remaining open,” the statement said.

The company operates 10 lumber and retail locations in Alaska, according to its website. It operates four manufacturing centers, including truss plants in Eklutna and Kenai.

Ross Noffsinger, Anchorage’s acting building official, said municipal officials are investigating this week’s collapse and the construction of the building to try to pinpoint what caused the failure.

Noffsinger said that an inspection in part of the building that did not collapse indicates that the most likely suspect at this point are inadequate metal gang nail plates. The plates join together wooden beams in roof trusses.

The metal plates in a key area of the trusses “lack sufficient size and/or are poorly placed,” he said in an email Thursday afternoon.

The plates appear to be a common denominator in the failures of multiple commercial building roofs in Anchorage in recent years, he said.

The Spenard Builders Supply building is the same kind that Anchorage officials have warned could be at high risk of failure from the current snow load: parallel chord truss construction and a flat roof, built in the 1980s, Boyd said. The building measures 275 to 300 feet long by 125 feet wide, according to fire officials.

“In this case, this roof failed fairly early in the season,” Noffsinger said.

Fourteen fire department units responded, along with the Anchorage Police Department, municipal street department officials, and representatives from Chugach Electric, Anchorage Water and Wastewater Utility and Enstar, Boyd said. Along with the collapse, responders contended with broken water lines that dumped up to a foot of water onto adjacent streets, he said.

First responders had cleared from the scene by Thursday morning. Several employees walked along the perimeter and surveyed the wreckage. Inside, an emergency light flashed and an alarm rang on repeat. The force of the collapse threw wooden boards and insulation toward neighboring homes.

Anchorage has experienced record snowfalls so far this season, with back-to-back November storms dropping several feet at once, followed by a windstorm in early December that pushed the accumulation into drifts. That was followed by higher temperatures, which can melt snow on roofs into ice dams that put more pressure on structures.

Last year also saw heavier-than-normal levels of snow atop buildings; at least 16 roofs were damaged in partial or full failures. A woman was killed and two others trapped in February when the roof of a South Anchorage gym collapsed.

A Spenard Builders Supply building in Soldotna collapsed in December 2022 after a series of storms dumped heavy snow on the Kenai Peninsula. The company’s Fairbanks store closed temporarily after part of the roof buckled in March 2021, according to local news reports at the time.

Noffsinger said snow loads in Anchorage now are in the range of 20 to 25 pounds per square foot — about the same as levels last winter when roofs were collapsing.

Many of the collapses occurred in the spring, following heavy snow in December 2022 that added significant pressure over a period of months.

This year’s record levels of snow that began in November create the possibility of another long winter of unusual stress on roofs, Noffsinger said.

”Time matters,” he said.

Noffsinger said the previous roof failures involving Spenard Builders Supply buildings took place outside the municipality’s jurisdiction, so officials don’t currently have details on those events. But he said they’ll try to learn more about the cause of the failure in those situations as well.

Anchorage code typically requires that buildings support a minimum of 40 pounds per square foot.

Municipal building authorities last month issued new guidance and urged property owners, particularly those who own older buildings with flat roofs, to clear snow from them, especially on commercial buildings constructed before 1990 with certain designs of wooden trusses supporting broad roofs.

“We will echo what the folks in the building department have been saying,” Boyd said Thursday morning, advising owners of older buildings or those responsible for building safety to “watch closely” for any signs of trouble and be aware that melting and wind could make accumulation look less significant than it is.

“They may not be able to hold the snow loads that we’re currently looking at because they’re just not up to what would be expected of structural code now,” he said.

Scott Hamel, chair of the Civil Engineering Department at the University of Alaska Anchorage, said most homeowners don’t need to worry at this point about the snow loads on their roofs.

Hamel said the city is still well below last winter’s peak snow load of 35 pounds per square foot. And homes typically don’t have the huge roof spans of commercial buildings, a relative safety factor.

He said flat-roofed homes with drainage issues that can cause excessive snow load in some areas, or with the problematic parallel chord truss designs with undersized metal plates that connect beams, might benefit from an inspection.

”If you have good drainage, there’s not too much to worry about,” Hamel said.

Anchorage Daily News reporter Tess Williams contributed.