Decorative concrete overlays need a bit of maintenance to protect their beauty and investment. This isn't difficult maintenance, so there is no need to put it off. For starters, seal decorative concrete overlays once a year to protect them. The sealant is available at any home improvement center and should be applied by manufacturers directions. To keep the overlay clean, regularly hose it down using medium pressure on a pressure washer or hose. If the overlay is dirty, use a mild household cleaning soap and a bristle mop to scrub it down. Be sure to rinse completely clean with clear water.