The company has extended its fiscal year by three months to June 2020 to cushion the three-month closure of most of its 100 construction sites in March last year.
Additional costs, particularly from the extended lockdown in Scotland through June, put the business in the red, compared to a trading profit of £ 16.7 million the year before. Sales also fell 10% over the longer period to £ 637 million.
Robertson took nearly £ 3.9 million in government maintenance payments to support workers. In the period from April to mid-June, around 1,100 employees were on vacation, with work gradually resuming until June and July.
In an exceptionally challenging year, net cash was almost halved to £ 34 million.
Chairman Bill Robertson said the company has now returned to normal trading at the targeted levels of productivity and profitability.
“With the currently secured order backlog, we are confident that the coming year will be a year of profit recovery as we adapt to the new working conditions”