It depends on the type of siding. Vinyl and aluminum siding can be damaged by power washing, while wood siding can be stained or water-logged if not properly cleaned and sealed after power washing. Consult with a professional to find out if power washing is recommended for your home's particular type of siding, and always follow their instructions to avoid damaging your home.

It's not necessarily bad for siding, but it can be if done improperly. Power washing can strip the paint or sealant off of the siding and cause it to deteriorate more quickly. It's important to use the correct amount of pressure and spray the correct direction so that the water doesn't hit the house at an angle and peel the paint.