Deck porches around our homes get algae and grime built up in the winter months. Most people think to pressure wash this grime off. In most cases all you need is a light chemical and some old fashioned elbow grease. Pressure washing your wood deck can strip the paint and leave marks in the wood permanently if done wrong. Pressure washing wood is alright when re-staining or re-painting afterwords, but If your looking to keep the finish and just clean up the dirt, a good scrub down and rinse can go a long way.