John Hughes, of Newark, was working in the outdoor yard of Caledonian Building Systems Ltd at Carlton-on-Trent, Nottinghamshire, on 20 February 2009.
He was helping a fork lift truck driver to raise an 11-tonne modular building unit off some blocks and a wheeled axle, on to a lorry, but the unstable load started to rock.
Hughes put his right hand on to the wooden block, to move it out of the way, but one end of the unit came down on his fingers.
His index finger was crushed and had to be amputated at the knuckle, but eighteen months later after continuing problems it was completely removed.
His middle finger was also damaged and Hughes was off work for twelve weeks in total.
A Health and Safety Executive investigation found the lifting operation was disorganised and the employees involved were not provided with clear information or instructions.
Caledonian Building Systems Ltd, of Glendale Gryfe Road, Bridge of Weir, Renfrewshire, pleaded guilty to breaching lifting and safety regulations.
Nottingham Magistrates fined the firm £15,000 yesterday and ordered it to pay costs of £7,328.
After the hearing HSE inspector Stuart Parry said: “This was a routine lifting operation for Caledonian Building Systems Ltd yet it was poorly assessed and planned and was conducted in a disorganised manner.
“Companies moving large loads with lift trucks should remember these basic legal requirements to ensure they protect their employees and anyone else who may be affected by their work.”