Roof of fourth commercial building collapses in Anchorage

The roof of a fourth commercial business collapsed in Anchorage early Friday after a season of heavy snowfall, at the 5401 Cordova St. business complex.

It was the second roof to buckle this week.

No one was hurt in the collapse Friday, which occurred over an unoccupied unit, said Ross Noffsinger, the acting building official for the Municipality of Anchorage.

The entire roof over the unit failed and its front and back walls bulged out, he said. It was the only roof in the commercial center that failed, he said.

The commercial center consists of three single-story buildings, each with several units side by side. Several businesses occupy the units. Tenants were asked to vacate the undamaged units until the snow load has been removed from each roof, Noffsinger said. The area is just south of International Airport Road, between the Old Seward Highway and C Street.

The Anchorage Fire Department said in a statement that it was dispatched to the site shortly after 9 a.m. Friday to investigate a suspected gas leak. Soon after, it learned that the roof above the unit had been destroyed.

The buildings at the complex were constructed in 1978, municipal property records show.

The roof framework is the same design that has been implicated as a likely cause of failure in most of the 20 roof collapses that have occurred this winter and last, when heavy snow also fell, Noffsinger said.

“This looks like same truss issue we have been messaging about,” he said.

The problematic roofs are flat and built with wooden, parallel-chord trusses, in buildings constructed before 1990. Metal gang plates that help hold the wooden beams together are often inadequately placed or undersized.

The owner of the building involved in Friday’s collapse had the trusses strengthened this summer, Noffsinger said.

The owner is listed as DDT, LLC, according to Anchorage property records.

An owner of the company declined to comment on Friday, and referred a phone call from a reporter to the municipal building department.

In November, local officials issued guidance to commercial building owners to keep roofs clear of accumulation in order to avoid risking catastrophic damage.

Municipal building officials also began to warn the public last winter about the flawed roof designs.

Recently, Noffsinger has also begun to warn homeowners that they should think about clearing snow from their roofs, assuming the heavy snow continues.

[Should you shovel your roof? A Q&A with an Anchorage building official.]

On Monday, the roof of a commercial warehouse caved at 7920 Schoon St. In late December, a roof at a distribution warehouse owned by Spenard Builders Supply collapsed, followed by a roof at a vacant, condemned warehouse in Midtown Anchorage that buckled. Last year, a woman was killed and two others trapped when the roof of a South Anchorage gym caved.

More than 7 feet of snow has fallen this winter. Much of it arrived early, creating an unusually long period for large snow loads to sit on roofs, adding to the possibility of failure, Noffsinger has said.

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

The Anchorage Fire Department on Friday said that 20 to 25 pounds of snow per square foot is sitting atop Anchorage roofs.

But the department added that wind loading and ice damming can cause loads to become concentrated in small sections, increasing the risk that a roof will be damaged.

The department said in the statement that it wanted to highlight the importance of clearing roofs of snow.

“A structural engineer is the best person to conduct a building evaluation and determine risk and/or safety,” the fire department said.

Access to two of the buildings was closed off with red “danger” tape late Friday afternoon. Part of East 54th Avenue near the damaged unit was closed off with “detour” barricades.

Lindsay Hobson, a spokesman with natural gas company Enstar, said the road closure was not related to concerns about natural gas.

She said the road was initially closed by the fire department. It remained closed due to concerns about further roof damage.

A gas line on the roof of the unit, likely providing heat, was damaged when the roof caved in, causing people to notice the smell of gas, she said.

But the Enstar facilities that bring gas to the unit’s meter were not damaged, she said.

The natural gas to the complex was initially turned off by the fire department.

But it has been restored, with the exception of the damaged unit, she said Friday evening.

Hobson said commercial buildings sometimes have exterior gas lines on roofs that feed heaters in buildings.

Snow shovelers on commercial buildings should be aware of those pipes as they shovel, to avoid damaging them, she said.