Caernarfon Crown Court heard that Andrew Wilding and his colleague were using pneumatic drills to break up an unsupported concrete floor on the first storey of a former hospital outbuilding at Plas Maldwyn site in Caersws which was being converted into residential accommodation.

During the breaking work in May 2008 the floor split and both men fell through to the ground below. A section of the broken floor slab fell on Wilding, causing life-threatening internal injuries.

An HSE investigation discovered that developer Gruffydd Charles Beynon-Thomas had failed to ensure the safety of workers by not properly planning structural work at an early stage.

Gruffydd Charles Beynon-Thomas, trading as Plas Maldwyn Developments, of Ty Gwyn Road, Caersws, Powys, pleaded guilty to safety breaches and was fined £7,500 and ordered to pay costs of £7,500

After the hearing, HSE inspector Chris Wilcox said: “People carrying out building refurbishment must ensure that structural work is properly planned and advice sought from a competent person, for example a structural engineer, at an early stage.

“The consequences in failing to recognise the risks inherent in this type of work can be significant.  This was a major incident that could easily have been fatal”