Both firms admitted failing to put proper procedures and safeguards in place to prevent painter Paul Welstead falling at East Croydon railway station on 7 January 2015.
Welstead, aged 31 at the time of the accident, suffered severe ligament damage and has been unable to return to work as an industrial painter since falling around three metres.
The companies were fined at Croydon Crown Court after admitting safety charges in a prosecution brought by the Office of Rail and Road (ORR).
The court heard that the two companies agreed the £12m contract with Network Rail to undertake the replacement of station floor surfaces, canopy roofs and cladding.
BAM Nuttall started work in January 2014 and later that year a third company, DRH, was asked by the existing contractors to supply industrial painters to undertake specialist tasks.
Welstead and a colleague were given a site induction when they arrived for work on 18 December, but they were not briefed on the risk assessment, which required work over the platforms to be undertaken at night, for workers to wear full body harnesses and for the waiting room below to be locked.
Returning to work on 7 January following the Christmas and New Year holiday, Welstead and his colleague were not given another safety briefing, nor were they warned about fragile roofs, and at 9.40am he fell through the unguarded suspended ceiling into the waiting room below.
Johnny Schute, Deputy Director, Policy, Strategy and Planning, said: “The fines handed out today send a powerful message to the industry that the safety of workers on the railways is absolutely paramount, and proper risk assessments and briefings must be carried out and followed.
“The ORR is committed to protecting the safety of workers and passengers and will not hesitate to take enforcement action when and where it is necessary.”