The son pulled his father to safety after he was trapped by rubble when the building collapsed during unsafe renovation work, a court has heard.
The pair, aged 51 and 20 from Penkridge, Staffordshire, who have asked not to be named, fell through two floors but avoided serious injury in the incident at High Street, Bilston on 25 June 2012.
They were working as bricklayers for Clark Brothers (Builders & Developers) Ltd of Bilston, which was prosecuted by the Health and Safety Executive (HSE) after an investigation revealed the company failed to properly plan, manage and supervise the refurbishment work.
Wolverhampton Magistrates' Court was told the father and son team were block-laying inside a former shop building when the second floor they were working on suddenly gave way.
The weight of the collapsing floor and block work was such that it smashed through the first floor beneath, and sent them crashing all the way to the ground floor, leaving the father buried under rubble. The son had to pull him free before both were taken to hospital for treatment. They were discharged later the same day after escaping with relatively minor injuries.
The collapse meant a section of the High Street had to be closed until a building control team had declared the structure safe.
HSE inspectors found that the refurbishment project was unsafe and immediately issued a prohibition notice stopping any further work at the site.
The court heard that Clark Brothers did not properly plan and supervise the work, and, failed to take suitable measures to protect those that may have been affected by the work whilst the building was being renovated.
Clark Brothers (Builders & Developers) Ltd, of High Street, Bilston, Wolverhampton, was fined £10,000 and ordered to pay £1,844 in costs after pleading guilty to breaching Section 3(1) of the Health and Safety at Work etc Act 1974.
Speaking after the hearing, HSE inspector Paul Cooper said: "Clark Brothers (Builders & Developers) Ltd made a number of serious errors in attempting to undertake this work without proper planning, training and supervision.
"A floor collapse, as with any unplanned demolition work, presents very serious dangers that can result in serious or fatal injury. The fact the father and son escaped relatively unharmed in this collapse is remarkable.
"The uncontrolled collapse of the building also posed a risk to members of the public who were out on the High Street that morning."