Neil Anson, a 44 year old self-employed plasterer from Wolverhampton, was struck by timber roof trusses being unloaded by a mobile crane from a lorry trailer at a construction site at Foster Avenue, Bilston last year.
The Health and Safety Executive (HSE) prosecuted Kent Road Construction and Fortmere Construction, both firms of Brierley Hill, following an investigation into the incident.
Wolverhampton Magistrates Court heard that on 10 June 2009, Anson was getting off the trailer when several packs of the roof trusses fell onto him, severely fracturing his right leg, elbow, hand and thumb.
A dozen of the large wooden structures, together weighing some 400kg, pinned Anson to the floor and another, larger, heavier pack also fell towards the stricken man but fortunately the pack hit a road sign that stopped it landing on him.
Kent Road Construction admitted breaching Regulation 8(1) of the Lifting Operations and Lifting Equipment Regulation 1998.
Fortmere Construction admitted breaching Regulation 14(1) of the Construction (Design and Management) Regulation 2007.
Kent Road Construction was fined £6,000 and ordered to pay £4,496 costs while Fortmere Construction was fined £4,000 and ordered to pay £899 costs.
HSE inspector Martin Overstall said: "Anson received very serious injuries as a result of this incident and had the falling timber hit his head, he would almost certainly have died.
"This case should remind companies managing construction sites and directing cranes to ensure all operators are properly trained and competent to do so. The law also requires companies that hire contractors to make reasonable checks that they are competent to carry out work on a construction site.
"In this case, the contractor failed to plan, supervise and carry out a safe lifting operation. The client company had not appointed a co-ordinator, one of whose roles would have been to advise the client on the competence of the contractor."