SafeWork NSW says the two carpenters were working near the base of the wall amid strong winds at the Carlingford site in August 2017 when it fell and pinned them both.

One 30-year-old worker died at the scene despite the efforts of other workers, who dug frantically to free him, while the other suffered scratch marks to his face and was treated for shock.

The wall had come down in winds reaching 80km/h.

NSW Bricklaying Pty Ltd was on Friday fined $500,000, Effective Building and Construction Pty Ltd was fined $60,000 and another company director, Jianen Wang, was fined $60,000 following a prosecution by SafeWork NSW over the incident.

"Each party responsible failed to apply appropriate risk management and safety measures, ultimately failing in their duty to protect workers," SafeWork NSW's Valerie Griswold said in a statement on Friday.

EBC was contracted to build a two-storey duplex in Carlingford in 2017 and hired WZY Development Pty Ltd and its director Mr Wang to manage activities, according to SafeWork.

Mr Wang had NSW Bricklaying build a 6.5 metre wall to divide the duplexes. It was later found to have been inadequately braced.

"Risks assessments were not completed at this site nor were temporary supports installed, safe work method statements implemented or adequate supervision provided to workers," Ms Griswold said.

"All of these things put the workers on site at significant risk."

EBC, NSWBL and Mr Wang have the right to appeal their sentences.

Australian Associated Press