About 30 workers from Bunnings Mount Maunganui walked off the job in protest at proposed changes for increased flexibility.
First Union retail and finance secretary Maxine Gay said the workers had learned the company was proposing a change that would remove the right to determine their start and finish times.
"The company is trying to remove mutual agreement and insert a clause that will allow management to chop and change those start and finish times at will," Ms Gay said.
"This means that a worker might be guaranteed 40 hours per fortnight, but then find that start and finish times chop and change." Ms Gay said more strikes were likely.
Bunnings has stated it would not make wholesale changes to its teams' roster patterns but that some changes would occur.
Bunnings stated any and all changes would take place in full consultation with staff with advance notice would be given, so that any significant commitments could be raised and taken into account.
The firm said it had put forward what it believed to be an industry-leading proposal covering wage rates and rosters, as part of current negotiations covered by individual employment agreements and First Union.