A series of COVID-19 restrictions breaches on residential construction sites was unforgivable, but mandatory vaccinations were not required for the sector, Chief Minister Andrew Barr said.
Mr Barr hoped the inspections were enough to deter builders from breaking the rules, and tough compliance checks would continue.
"These breaches are unforgivable. They put employees and the general community at risk. It's simply not good enough and the sites have been shut down," Mr Barr said.
Four residential construction sites were on Thursday closed for "serious" breaches of public health restrictions.
Inspectors from WorkSafe ACT issued eight prohibition notices and 27 improvements in a three-and-a- half hour period in Strathnairn in west Belconnen.
Master Builders ACT chief executive Michael Hopkins said the association strongly supported the enforcement of COVID safety practices on building and construction sites.
"We understand that the industry continues to face delays and that the current restrictions mean working at 100 per cent capacity is not an option. However, this is no reason to compromise on the COVID-safe practices that are mandatory," Mr Hopkins said.

Mr Barr was pleased to hear from the WorkSafe commissioner there was strong compliance in another part of the city, and members of the Master Builders association and the Housing Industry Association had very strong compliance.
The Chief Minister said strong vaccine take-up in the territory meant vaccine mandates were not required for the construction industry.
"I appreciate everyone wants to know every single person they might come into contact with in a high-risk setting would be vaccinated. It is generally the case that most people are now [vaccinated] in those settings," he said.
Residential construction was shut for a month after the ACT was locked down on August 12, with the ACT government expressing caution about reopening the sector due to its track record complying with safety rules.
Large-scale construction sites returned to work on September 3, with residential construction allowed to resume on Friday, September 10.