Sheffield Magistrates’ Court heard how, on 18 May 2018, the operative was working on the first floor of a house being built at a development property on North Street.
He was using a trowel to remove excess mortar from the back of breeze blocks, when he stepped backwards and fell through an unprotected stairway opening onto the concrete ground floor.
He suffered two fractured ribs and contusions.
An HSE investigation found that Trumax Building had failed to install a proprietary guardrail system or traditional scaffold guardrails around the perimeter of the opening.
Trumax Building Ltd of Doncaster pleaded guilty to breaching safety regulations and was fined £10,000 and ordered to pay £803 in costs.
After the hearing, HSE inspector Stuart Whitesmith said: “This incident could so easily have been avoided by simply carrying out correct control measures and safe working practices, particularly to protect inexperienced workers.
“In this case someone suffered serious injuries which could been easily avoided by installing guardrails around the opening, to prevent workers falling from height.”