Westminster Magistrates’ Court also ordered managing director of C J Langs, Kewie Doherty, to carry out 150 hours of unpaid community work. His company was also fined £80,000.
The court heard how HSE inspectors had visited the site in Sherborne Gardens, London, following an incident in January 2017.
They found evidence of poor health and safety conditions on site including dangerous work at height, a lack of suitable equipment, and untrained operatives working without adequate supervision.
A subsequent investigation found the construction company failed to plan, manage and monitor the work on site and Doherty was responsible for the poor conditions on site.
C J Langs and Doherty pleaded guilty to breaching safety regulations.
Speaking after the hearing, HSE inspector Kevin Smith said: “Dutyholders should be aware that HSE will not hesitate to take appropriate enforcement action against those that fall below the required standards.”