Melling began his stint at Curtins in 1981 as an Apprentice before progressing to the Board of Directors in 1999. He then accepted his position as CEO in 2004 and was responsible for expanding the firm to 14 locations in the UK.
Melling also enabled the firms appointments on project masterplans worth in excess £1bn. He recently supported the business through an employee-owned trust transition.
Board director Paul Menzies said: "Where we were once just a civil and structural engineering firm, now we're also a business with heart."
The firm has appointed Neil Parkinson as the next CEO. He will start his new position on 1st January 2025.
Melling said: "I can think of no-one better than Neil to take on this role. He knows the business inside out, and his passion and experience are the perfect fit to continue to build on Curtins' legacy and lead the business into what I'm sure will be a bright and exciting future."