Stephen McKeown hurt his back in the fall, which happened after he carried out salting work at St Francis' Primary, Port Glasgow, in November 2010.
The 61-year-old, who had worked for 18 years as a janitor in various schools, sued Inverlcyde Council over the incident.
A judge said the council's gritting system was reasonable, but existed only on paper and was never put into action.
The court heard that damages were agreed at £30,000 but the council did not accept liability, instead blaming the janitor.
Mr McKeown had fallen against a wall as he used a litter picker, the court heard.
Judge Lord Burns said Mr McKeown was not to blame, ordering Inverclyde Council to pay damages.