Work stops on city sites.
Work was stopped as part of a HSE crackdown on unsafe practices.
Inspectors visited 24 contractors on refurbishment sites in the city and served four prohibition notices, effectively stopping work due to concerns about working at height and electrical issues.
Two improvement notices were also issued to contractors where there was a lack of adequate welfare facilities and the use of stepladders without carrying out a risk assessment.
It is the second time this year that HSE inspectors have carried out random checks.