Cleaning the render is generally advised after a few years. This will sharpen the aesthetic look and rejuvenate the finished facade by removing any organic growth, bird droppings and film of weathering found on surface.
The surface can be cleaned using a pressure washer with clean water and a low concentration of mild detergent. The washer should be set on fan application, not high power (very high pressure washers can damage the render surface). Carefully clean the render surface, in a controlled fashion, working from top to bottom.