Striker walks the line in front of the jobsite at the Canadian Museum of Human Rights, Monday. (CBC)

Picket lines went up Monday at high profile building sites in Winnipeg, including James Richardson International Airport and the Canadian Museum for Human Rights at the Forks.

Members of the United Association of Plumbers and Pipefitters voted Sunday against a contract settlement with employers. The workers are reportedly seeking an 18 percent wage increase over three years.

A dozen or so construction workers wearing placards formed a picket line at the museum construction site early Monday. And pickets appeared at the airport as well.

Strike captain Rick Fournier said unionized plumbers and pipefitters overwhelmingly rejected a three percent per year wage offer from the Construction Labour Relations Association however CLRA spokesman Peter Wightman said the employer offered the union a 10.4 percent wage boost over three years.

Fournier said members of his union local are among the lowest paid workers in the trade in Canada.

Fournier said other trades including unionized iron workers and carpenters are expected to honour their picket lines.

"The CLRA has to deal with all these unions," said Fournier. "They're all in negotiations, they'll all be going to the wall, I'll put it that way. Some of them may have to walk on a line and we won't cross their line so they won't cross our line."

Museum spokesperson Angela Cassie said she doesn't expect a major delay on the project just yet.

"Those are not particularly trades that have a lot of work currently on the site," she said.

Airport construction manager Steve Smith of EllisDon Construction said as many as 450 workers at the airport project could be affected if the picket lines by plumbers and pipefitters remain in place for any extended period of time.

"It's obviously going to be a delay to the end date, absolutely," said Smith. "It'll be a critical delay to the project."

The new airport terminal is scheduled to open in the fall.