Washing your stuff, lawn furniture or your pets outside on concrete sidewalks, pavers, poolside, etc. may leave a soapy residue that you will have to clean off afterwards. This is more difficult to do if it is left to bake into the porous surface. Additionally the washing area will become cleaner and then the surrounding area and may look different until the rest of the area is cleaned. Please keep this mind when planning big washing projects and if possible do it on the lawn.