John Holdom pleaded guilty to health and safety breaches after a subcontractor fell 4m through a temporary timber handrail that gave way whilst he worked on the first floor of the building.
He suffered two broken wrists and bruising.
HSE prosecuting inspector Karl Raw said: "Sufficient measures had not been taken to support or protect anyone from falling from the landing area and the wooden handrail was not sufficiently secured.
"Many incidents could be avoided if companies ensured that they had thought through a safe way of tackling a job, provided all necessary protective equipment and safeguards to minimise risk to anyone on or near the site. The handrail was quite clearly unsatisfactory."
The HSE said that last year 10 employees and 13 self-employed were killed with 3,409 seriously injured after falling from height.
Mr Holdom was also ordered to pay £1,614 in costs.