We've been using a product called Green to Clean, it is highly effective at removing and preventing moss, bacteria, lichen, algae, fungi, viruses and mould on all hard external surfaces, prolonging and protecting new and old surfaces, helping to reduce safety hazards and even brightening & cleaning as it goes. It also makes a very effective patio cleaner and driveway cleaner.
All you need to do is spray and walk away, within a few days you will see it start to work.
