Reading Magistrates’ Court heard how concerns were raised by both workers and members of the public.
HSE inspectors made a number of visits during 2015 to two project sites where In House Design & Build Ltd was the principal contractor and identified a number of serious safety failings.
In House is the £62m turnover construction and project management arm of the Soho House private members club and oversees work on its developments.
An HSE investigation found that over a four-month period at the first site, and despite several enforcement notices being served, the company still failed to adequately address the risks.
The notices served were for breaches including unsafe work at height, working in unstable deep excavations and inadequate arrangements for planning, managing and monitoring construction work.
Further similar concerns were found later in the year at the second site where very poor welfare arrangements were also noted.
In House Design and Build Limited, of Dean Street, London, pleaded guilty to two breaches under the CDM Regulations and was fined £100,000.
Project manager, Neil Crow, of London, who had been in charge of operations at both sites, pleaded guilty to two CDM and safety breaches and was fined £15,000.
Full costs of £15,000 were also awarded.
Speaking after the hearing, HSE inspector Dominic Goacher said: “Principal contractors and their managers have a duty to ensure risks to workers are managed throughout the construction phase of projects.
“This case serves as a reminder to those responsible of the importance of ensuring construction work is properly planned, managed and monitored so that serious risks are identified and eliminated or controlled.
“It was only by good fortune that someone was not seriously injured or killed in this instance.”