Burnley-based engineering firm Lupton & Place has been prosecuted by the Health & Safety Executive following a fall at its factory on Athletic Street on 23 September 2010.
Reedley Magistrates' Court was told the company, which employs almost 150 people, allowed the contractor to work along a section of the roof without anything in place to stop him falling.
The 67-year-old, who has asked not to be named, was fixing a leak on the roof when he lost his balance, stepped backwards and fell through one of the roof panels. He escaped injury after landing on a machine cover more than four metres below.
Lupton & Place admitted breaching Section 3(1) of the Health and Safety at Work Act 1974 by failing to ensure the safety of workers. The company, which produces parts for the automotive, defence and electronics industries, was fined £6,000 and ordered to pay £6,250 in prosecution costs on 11 August 2011.
Speaking after the hearing, the investigating inspector at HSE, Matt Lea, said: "The contractor had been employed by the firm for more than 30 years, but nothing was done to monitor or control the work he was doing.
"A company the size of Lupton & Place should have requested method statements and risk assessments from him to make sure the work could be done safely.
"It would have been much more sensible to use a cherry picker to fix the leak, instead of allowing someone to walk along the roof and work on the fragile surface.
"The handyman was very lucky to come away from the incident with just bruising. He could easily have suffered a major injury or even been killed in a fall of that distance."
Last year, more than 4,000 employees suffered a major injury as a result of a fall from height at work and 12 were killed in the UK.