The work safety watchdog WorkSafe has closed 18 construction sites in the third series of raids in three weeks.
After ordering a halt to activity on 11 sites two weeks ago, it took action against four residential construction projects in north Canberra last week.
It's now closed the sites in Watson run by five different companies.
WorkSafe said action against one company responsible for the most breaches came "when they were unable to find any evidence that the company had safe work management systems in place."
"This is an appalling number of safety concerns which could easily have led to fatalities or injuries in our community, WorkSafe Commissioner Jacqueline Agius said.
"I want to send a clear message to employers that it's time to lift their game and start making safety a priority for their workers."
The safety watchdog targeted Watson in the latest phase of what it calls "Operation Safe Prospect".
The previous raids were because scaffolding was inadequate so workers were not protected from potentially fatal falls.
Commissioner Agius, said such breaches were "far too common and should not be occurring.
"We are continually seeing the same types of safety issues at residential construction sites across the ACT," she said.
"Basic health and safety requirements, like having proper scaffolding and fall protection is not negotiable.
"We will keep issuing notices to companies who blatantly disregard their legal obligations to maintain a safe workplace.
"Every employer and worker should be prioritising their safety." The organisation is not naming any of the companies or sites.