Sat Dhaiwal joined A-Plant in 1993 and became chief executive in 2002.
In 1993, A-Plant had 52 locations and had an annual turnover of £27m. The business has since grown to 179 locations and had an annual turnover of over £400m in the 2016/17 financial year.
Geoff Drabble, chief executive of parent company Ashtead, said: “This has been well planned for some time. By stepping down next year, there is a 12-month handover period until Richard Thomas takes over. Although it isn’t the time to say goodbye yet, myself and the board would like to thank Sat for the tremendous job he has done as CEO of A-Plant and for his contribution to the growth of the company.”