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Expanded Use of Wood-frames in Some Tall Buildings Questioned in Construction Fires

Late last year, we noted on Construction Citizen that one of the emerging trends in commercial construction is that wood is making more appearances as the material of choice for the frames of some tall buildings in the United States and around the world. 

At the time, Smithsonian.com had just published an article about a building in Minnesota called T3 that was on track to be the tallest wooden structure in this country. The irony of T3's cutting edge technology was “that its cutting-edge nature rests on an old-school material: wood," as the folks at the Smithsonian put it. 

Now, the expanded use of wood-frame construction in many residential buildings is under the microscope after a spate of construction fires in California. 

It turns out that in 2008, the state's building codes were changed to allow for the greater use of wood frames for certain buildings. 

The question was posed by the folks at the San Francisco Chronicle

In 2008, the state’s codes were rewritten to allow buildings under eight stories tall to use wood framing, over two floors of concrete. The construction method generally is much cheaper than the old way, which required “noncombustible” exterior walls — typically, concrete and steel studs — from top to bottom.

But experts tell us all that wood makes the buildings especially vulnerable during construction, before sprinklers and flame-resistant sheet rock are in place.

That proved to be the case in 2014, when a six-story, 124-unit apartment complex under construction in San Francisco’s Mission Bay went went up in flames. The fire was later ruled an accident.

The latest fire, last Friday, proved to be very difficult for first responders to deal with. ABC 7 in San Francisco reports

Firefighters say they had to take a defensive stance against this one because of its size and the threat from the scaffolding and a wildly swinging crane.

"When the crane takes on that much heat, it starts to spin," said Battalion Chief Zoraida Diaz. "So that was one of our major concerns fighting this fire."

The crane didn't collapse, but part of the building did. No firefighters were hurt, they were at a safe distance when it happened.

Firefighters and police say they knew it was dire to get the area evacuated as soon as possible. 

You can check out images from the fire below: