Pressure or power washing is an effective way to clean large surfaces without a lot of scrubbing. A pressure washer can remove debris, paint, oil or grease that is stuck or encrusted on a surface. It works best on non-porous surfaces like concrete and will work well in a concrete basement. It is not recommended as a cleaning solution for a basement with wooden walls or dirt floors.
Remove all items from the basement before pressure washing it. A pressure washer sprays hard and water droplets will get on everything. Pictures should be taken down and anything that can be damaged by the pressure or water must be removed. Anything that can't be moved, but should be protected, can be wrapped in or covered with plastic and secured with duct tape. Check for a drain in your basement. If there is one, make sure it's clear. If there isn't a drain in the basement, reconsider using a pressure washer to clean it. You will need a lot of towels, rags or a shop vacuum to clean up the water.
Washing the Basement
Rent a pressure washer with the least amount of pressure needed to do the job. Pressure washers come in sizes from 1,200 pounds per square (psi) inch to 3,000 psi. A 1,200-to-1,500 psi washer is safe for most basement cleaning projects. A stronger one should be used by someone with experience using a pressure washer. Mix the detergent in your washer as recommended by the manufacturer and spray your basement walls, starting from about three feet away. Work your way closer as you get more comfortable using it.
Practice using the pressure washer outside on a wall or the sidewalk before bringing it inside. The extremely high pressure can be surprising at first and takes some getting used to. Practice using different angle tips as well. It's best to determine which tip will work best in your basement before using the washer inside.
Never point a pressure washer at anyone, as it can cause injury. Wear safety goggles to protect yourself from the splattering water. Make sure that all electrical outlets and any other devices in your basement are covered or unplugged. While it's not likely that you'll break a window with a pressure washer, it is entirely possible, so covering a window or being aware of it and staying away from it is highly recommended. Spraying a window can also drive water into the frame which can cause mildew and mold to breed later.