Around 100 electricians walked out of the Corus steel plant in Redcar on Monday of this week.
Not one contractor for Balfour Beatty went into work on the site.
Engineering construction workers at sites across Britain were set to walk out on Wednesday of this week in a dispute over pay. Sites include Ratcliffe, Stanlow Grangemouth Sellafield, Saltend and Runcorn.
Redcar workers leafleted the workforce on Monday to publicise the official protest.
They blocked the road, causing a long tailback of cars.