From the moment you walk out your front door , Exterior dirt, Algae-Mold-Fungus creates an image of darkness, Concrete is suppose to look bright grey not black moldy looking. Now your investment is looking pretty dingy. Everyone has a pressure washer, and we all know how labor intensive it is. So we ignore the inevitable for as long as we can. Call SWP to turn it back looking new again , ye it cost for a pro to do it, however it will stay like that for better then a year. You didnt waste your time doing it and hoping it was already done. Call for an estimate .