 The design of the Class 16 closely followed that of Hendrie's Class 15 4-8-2 Mountain type which was introduced at the same time from the same builders and many parts were made interchangeable.The cylinders were arranged outside the plate frames, with the piston valves above the cylinders and actuated by Walschaerts valve gear.The boilers were equipped with superheaters and had Belpaire fireboxes.