Sandwell Magistrates’ Court heard that the 19-year-old worker was standing on a tower scaffold in the empty swimming pool, attempting to cut canvas coverings from wooden roof beams.
The scaffold was too high to fit under the beams so he started to take off the handrails.
Meanwhile at ground level, the site manager, who is also the apprentice’s father, and another employee gave the tower a nudge to help get the handrails off, causing it to topple and fall.
The teenager, from Bedfordshire, fell and landed with such force that his hard hat broke and he suffered a fractured skull.
He also shattered his ankle and is still off work following the accident on 4 October 2013.
An HSE investigation found Pellikaan had failed to ensure the work on the roof beams was properly planned and carried out safely.
The scaffold had been put on a slope within the pool and no outriggers had been used to stabilise it.
Pellikaan of Gutter Lane, London, was fined £12,000 and ordered to pay £1,046 in costs after pleading guilty to breaching safety regulations.
After the hearing, HSE inspector Gareth Langston said: “This incident was entirely preventable and shows the importance of selecting the right equipment for the job.
“Tower scaffolds can be useful tools but should not be used on a slope when not levelled and should always be used with outriggers.
“The following week painters were due to arrive with a stable and versatile mobile elevating work platform which would have been much better suited to this job.
“Had Pellikaan waited for this equipment to come on site they would not have tried to use an unsuitable scaffold and a young man would not have suffered a painful injury that could have quite easily proved fatal.”