Nick Bake runs a construction firm in Blaine, and he's getting a little frustrated as he searches for more workers.

He recently hired four entry-level carpenters. He agreed to the wages they asked for — about $14 per hour — plus health insurance, and he was willing to train them.

But when it came time for work, they didn't show up.

"It's terribly hard to find construction workers right now," said Bake, owner of Suburban Framing, a firm with 25 employees year-round. "We're just trying to get bodies on the job site."

A downtown commercial building boom, recession-era exodus from the building trades and the retirements of thousands of skilled baby boomers are leaving construction crews short of labor. And the shortage is starting to push building costs upward as contractors struggle to maintain a skilled workforce.

General contractors are paying more per square foot than they did three years ago, as they compete for material and work to meet what they see as the increasingly high price of building regulations. Labor becomes yet another factor steadily driving up cost.

"Are costs moving up? Yes, they are," said Kelly Doran, owner of Doran Companies. "But it's not like all the sudden they've doubled or gone up 50 percent."

Just as the skyline in downtown Minneapolis is crowded with cranes, sites on Lake Street, Washington Avenue and Portland Avenue are crowded with workers in hard hats. The city's building boom is driving an emerging labor shortage felt by contractors around the Twin Cities. Industry leaders worry that a thin supply of certain types of construction workers is a looming problem.

Contractors in the state believe carpenters, equipment operators and laborers are becoming especially difficult to hire, according to a November survey from the Associated General Contractors of Minnesota. Masons and truck drivers are also difficult to find.

Before the housing market imploded, construction employed 132,000 Minnesotans. That number fell to 86,000 in 2010 as construction laborers left their professions for work in other industries or took early retirement.

There was so little demand for residential construction workers that wages fell about 25 percent, said Scott Gertjejansen, a branch manager for Carpentry Contractors, which bills itself as the largest residential framing company in the Twin Cities.

The industry has slowly recovered, and wages are part of the way back. Had the homebuilding market not slowed down in the second half of 2014, Gertjejansen said he would already lack the workers he needs to get projects completed. He expects to have a problem in 2015.

Every time he passes one of the apartment projects in downtown Minneapolis, or the new Vikings stadium, or even the Saints stadium in St. Paul, he looks at the workers in hard hats and thinks about his own labor needs.

"We're always defending against the commercial work," Gertjejansen said. "Right now, I think they're winning."

Commercial projects have drawn not only from the limited pool of existing construction workers, but they're also attracting newcomers. "Everybody's fighting for that new graduate from the tech schools," Gertjejansen said.

A slow rebound

Construction hiring has been gradually increasing since the industry collapsed during the recession, but it's not back to pre-crisis levels.

"Construction has definitely gotten better, but it's still not to where it once was," Doran said. "Multifamily's hot right now, but there's not tons of other stuff being built."

The number of construction jobs in Minnesota rose to 108,000 in November. Summer openings in the industry have steadily risen for the past five years, to more than 4,000 in June, the highest level since 2005.

Despite lingering uncertainty in the national housing market, people like David Siegel, director of the Builders Association of the Twin Cities, are worried that the workforce won't be equal to the work in the future. "I think there is a shortage now, and I frankly think it's going to get more severe," he said.

The average homebuilder nationally is 55 years old, Siegel said, an age that's not ­ideal for climbing around on rafters and plywood roofs.

"It gets hard to swing a hammer when you're 55 and 60 — it gets tougher," he said.

School enrollments are below what they need to be to fill the pipeline with workers, and people who left construction for the oil industry or other types of jobs are reluctant to come back.

The tightness of the labor market is forcing subcontractors like Bake, who owns Suburban Framing, to increase what they charge in order to hire the people they need. He raised his prices about $1.50 per square foot earlier this year, in order to pay for more expensive labor.

"This summer, I gave guys $5-an-hour raises," he said. "Because if I didn't, they would have gone somewhere else."

Adam Belz • 612-673-4405 Twitter: @adambelz