Mohammed Unees pleaded guilty to three safety breaches at Sheffield Magistrates' Court after a block and beam floor collapsed at one of his sites in Sheffield in September 2007.
The Health and Safety Executive said the blocks, which had been “illegally and dangerously” stored on the highway, were being transferred onto the recently constructed block and beam floor by three migrant workers who were working unsupervised and late into the evening.
The overloaded floor collapsed causing one of the men to fall three metres to the concrete floor below where he was hit by falling masonry. The injured man, who had to crawl for assistance, received serious back injuries.
The HSE said work had continued on site the following day despite the collapse and an unprotected hole that had appeared in the floor. As a consequence all work was halted by a prohibition notice.
HM inspector of health and safety John Rowe said: "If there is no supervision and management of a site it makes the likelihood of an accident of this type much greater.
"Property developers need to recognise their legal duties as clients and contractors and take steps to comply with the law".
The second charge resulted from an inspection one month later, when the HSE said Mr Unees had failed to ensure the scaffolding was in safe condition or prevent the risk of injury from a possible internal fall into the stairwell void.
The third charge was for failing to prepare a health and safety plan before construction work began on the site.
Mr Unees was fined a total of £4,000 and ordered to pay full costs of £986.