While most types of siding are low-maintenance, it's important to remember that it still needs to be cleaned and maintained. Siding can lose its appeal if not treated properly. Pressure washing is common to clean vinyl or metal siding of your house. A safer alternative you can use a mild detergent and a soft-bristled brush to clean it. To clean your house siding, divide it into sections, starting with the part that is most noticeable and working your way down.