Westminster Magistrates Court was told that a Health and Safety Executive (HSE) inspection at Dudley House in Hounslow on 23 May 2018 had identified a number of work at height issues.
The inspector found several unprotected edges where a person could fall a significant distance and also a floor that was being removed by a handheld breaker while workers were standing next to it.
STS Constructions had also failed to put any measures in place to prevent workers from falling if the floor collapsed.
The HSE found the firm's risk assessment had identified measures that needed to be implemented. However, these were not actioned.
STS Constructions of North London Business Park pleaded guilty to breaching reg 6(3) of the Work at Height Regulations 2005. In addition to the fine, the company must also pay £1,135 costs.