EMERYVILLE (KPIX 5) — After yet another large fire at a Bay Area construction site, there is new scrutiny on the building techniques that turn unfinished projects into a perfect opportunity for arsonists.

Developers believe arsonists know exactly when to strike. A 2009, building code change allows developers to increase the use of wood framing for up to five floors above the buildings concrete base.

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While it makes the projects more profitable, it also comes with a risk. ”The people that are setting these fires, and I think they are people that are setting them, are choosing the absolute best right to do it,” said Michael Ghielmetti of Signature Developers.

Once completed, wood-framed buildings are as safe as anything made of concrete or steel. But industry insiders say using wood also carries a risk when the wood framing is fully exposed.

“A certain point in a development when the property is most vulnerable,” said Greg McConnell with Oakland non-profit Jobs and Housing Coalition.

“It”s almost like a chimney, so the fire goes up through it,” said Ghielmetti.

“That’s all wasted money that ultimately goes into the cost of housing and just makes the housing crisis worse,” said McConnell.

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Wood is used to save money on the projects, versus the alternative. “The option would be steel framing … about 40 percent more than wood framing,” said McConnell.

Ghielmetti said if developers had to pay more, several current Bay Area projects would not have been built. In addition, the only way for some projects to get financing is to go with wood. “Everything else is too expensive,” he said.

So the downside to wood is that it creates that window when an arsonist could send it all up in smoke. The fires are delaying these projects for three to six months depending on the building, said Ghielmetti.

That window of vulnerability, along with the ongoing fires, now has builders paying a new cost – for added security.

“They’ve got motion detectors, dogs, barbed wire, 24/7 monitoring,” said McConnell.

It’s a situation that is forcing developers to make a business decision. “Less housing is produced because these projects don’t pencil,” said Ghielmetti. “Even the guy who makes the deli sandwiches, if he can’t make money selling a turkey sandwich, he’s not going to sell a turkey sandwich.”

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An array of security cameras and other surveillance systems are now the new norm at construction sites. Other changes being sought for large developments include having sprinkler systems and drywall installed earlier to minimize any fire damage.