MIAMI — First it was drywall, then it was the skyrocketing cost of concrete pushing up the overall price of construction. Now copper is the latest raw material with rapid price increases that is affecting companies from Miami to Shanghai.

Demand for copper has more than tripled the price of the metal, used in plumbing and electrical work, over the past few years. Last month, copper traded at a record $4.04 a pound.

"It's nearing the price of cheap gold," says Walid Wahab, president of Wahab Construction, a firm that specializes in high-end interior construction. Wahab said he was shocked recently when pricing one project to find that the costs to wire the building had tripled.

While essential building materials such as concrete, structural steel and drywall have leveled off in price, that's not true for copper, a conductor used to wire not just electricity but also telephone and data lines in buildings.

"What we see is that the volatility in the pricing of construction materials is beginning to settle down, except for copper," said Kent Long, a senior vice president with Centex Construction, Florida's largest general contractor.

While the recent spike in prices is hitting electrical contractors especially hard, it shouldn't have a big effect on overall construction costs. Contractors estimate that electrical work usually accounts for about 10 percent to 20 percent of a project's total cost; of that, copper is about 1 percent to 2 percent.

Compare that to concrete, which can account for as much as 40 percent of project costs.

But for the companies that do the electrical work for buildings, "our exposure to copper is pretty large," said George Haufler, president of Daniel Electrical Contractors in West Miami-Dade. The electrical contractor, owned by Texas-based Integrated Electrical Services, wires many of the new commercial and residential developments in south Florida.

When copper hit that peak in May, that meant Daniel was paying about $4 a pound, rather than the $2 of six months earlier, Haufler said. The price has since dropped back to about $3.50.

"It's one of those things, after you see it hit the ceiling, when it's a foot below it doesn't seem that bad," he said. "We had a bet about what was going to hit $3 first — a gallon of unleaded gas or copper. Copper hit it first."

Haufler says it's a global supply-and-demand situation that's driving the numbers now.

Vast construction in China has been one of the main drivers of demand worldwide. But recent strikes and other labor disputes at copper mines, most recently in Mexico, have also restricted supply.

UBS AG said in a recent note that it expects copper supply to increase more than 5 percent but demand to rise almost 6 percent, according to Bloomberg News. That deficit should keep copper prices high. UBS expects copper to average $2.80 a pound for the year.

The only alternative to copper wiring is aluminum, which is increasingly more affordable, according to Haufler, who noted that sometimes the savings can be as much as $500,000, depending on the size of the building. But copper has a lower resistance and is a better conductor than aluminum.