Archaeologists working at a medieval site on Aungier Street have downed tools for the day in a row over pay.
They're hired by the Irish Archaeological Consultancy, which is being accused of paying much lower rates than rival firms.
James Kyle from Unite says members voted to take action after the company refused to meet for talks.
"Some of our members who have 9-10 years' experience and a Masters degree are earning €11.50 an hour, other companies are paying €17.50 an hour for the same work", he said.
IAC says it deals directly with staff on contractual matters, and says it's already paying up to 4% more than the rate last requested by unions.
In a statement, the company explained that "Earlier this Spring, the trade union Unite circulated a letter throughout the commercial archaeology sector, seeking additional increases in pay/rates."
It says it has been "offering salary packages on projects, including our site at Aungier St., at, or up to 4% above those rates."