A builder's been hit with an $18,000 fine in the Christchurch District Court today for his blatant disregard for his employees' safety.

In 2013, Grant Collins breached a prohibition notice from WorkSafe New Zealand after inspectors found his employees repairing a roof without fall protection.

He refused to get workers down from the roof and when inspectors returned to the site they found he'd ignored the prohibition notice to stop work.

WorkSafe New Zealand's Chief Inspector Keith Stewart says his actions were unacceptable and he put his staff at great risk.