Specialist drilling contractor Stephen Harrison was employed by Jehu Project Services to carry out refurbishment work at a care home in Pontcanna, Cardiff.
Harrison stepped off the tower scaffold on 28 July 2015, and onto a loose concrete block on the ground floor. He fell backwards, head first, into a rubble-filled skip at the bottom of the lift pit.
A nearby specialist fire and rescue team stabilised Harrison and then attached him to the hook of a tower crane to winch him out of the pit. He was taken to hospital, where he stayed for 18 days, with fractured vertebrae, five broken ribs and a punctured lung. He was not paralysed but his injuries were life changing; he will not return to work.
Jehu had fitted lightweight barriers around the edges of the drop and filled the bottom of the pit with beanbags before the accident. However they were later removed because they were in the way of other contractors.
The Health and Safety Executive (HSE) found the management and supervision of the construction site was ineffective. It said the construction plan failed to properly consider the risks of working on tower scaffolds and there was a lack of an effective temporary works management system.
Jehu pleaded guilty to breaching reg 13(1) of the Construction (Design and Management) Regulations 2015 and reg 6(3) of the Work at Height Regulations, which cover ensuring construction work is carried out without risks to health or safety and preventing workers being injured by falls. It was fined £143,000 plus £15,029 costs.
Following the accident, all of the danger areas were fenced with scaffolding.
HSE inspector Liam Osborne said: "Jehu had been given many warnings in the past by HSE about the lack of effective planning, managing and monitoring on their construction sites, as well as warnings about unsafe working at height. [Newport Crown Court] heard some really positive steps the company is now taking to put these matters right, including making substantial management changes.
"There is a clear hierarchy for managing work at height risks; site managers need to prevent it if possible and then provide suitable fixed barriers. Lower-order measures, such as soft-landing systems or the use of harnesses should only be selected as a last resort and if it is safe and appropriate to do so."