Health and Safety Executive inspector Tariq Khan said the man was “lucky to be alive” after the fall.
Staffordshire Magistrates’ Court heard two workers at the Burton-on-Trent company had been renewing the roof of a large industrial unit in Uttoxeter when the incident occurred in April 2007.
One of the men working in the valley gutter, fell onto the neighbouring roof pitch which gave way causing him to fall more than 4.5m onto a concrete floor below.
He sustained serious injuries but has been able to return to work.
Mr Khan said sufficient measures had not been taken to protect anyone from falling off or through the “fragile” roofing.
He said: “There was also inadequate supervision of the work on a roof measuring in excess of 80m long and 80m wide.
“The employee who fell is lucky to be alive; we would not normally expect someone falling from that height onto a concrete floor to survive.”
The company was also ordered to pay £3,138 in costs after pleading guilty to the breach of the Health & Safety at Work Act.