The teenage worker suffered bad bruising to his back but no broken bones after his fall during work to install solar panels by electrical contractor Austin Gregg, of Masham.
It was only his third day at work.
Northalerton Magistrates heard that Gregg – trading as Gregg Electrical – had two apprentices working with him 0n June 26 2013.
When the incident happened, he was on the roof of another shed planning the fitting work.
The 16-year-old was on the ground tidying up when he was asked by the other apprentice if he would fetch a tool.
Without thinking to put a harness on, the youngster went on to the roof, stumbled and trod on a partially-covered rooflight which gave way, sending him crashing through to land on the concrete floor below.
HSE’s investigation found that Austin Gregg had taken some precautions but they were either insufficient or incomplete.
Fragile rooflights were partially covered and harnesses had been provided with lanyards but fixing points were not adequate or tested.
Austin Gregg, of Masham, North Yorkshire, was fined £2,000 and ordered to pay £505 in costs after admitting a safety breach.
After the hearing, HSE Inspector Julian Franklin said: “This young man certainly had a close shave. Falling from height remains one of the biggest causes of death and major injury.
“It is crucial that employers put safety precautions in place for working at height, whether the job lasts ten minutes or ten days.
“The risks of working on fragile roofs are well recognised and there is no excuse for putting workers at unnecessary risk of serious injury, or even death.
“It is particularly important to ensure that vulnerable young people, new to the working environment, are given very close supervision, clear instructions and not exposed to risks that they may not be able to envisage.”