Why pressure wash before an exterior paint or stain job?

The first if not one of the first things a solid painter needs to do before applying any paint or stain to a large surface is pressure wash. Some may think this is not an important step, but it is one you don't want to skip if you want the work, you just paid for to last. Pressure washing before any paint or stain job, done correctly will remove loose paint, dirt, dust, debris, grime, bird poop, spider webs, dead bugs and other natural markings from the elements. If you do have other stains or markings on the surface, special cleaners may be needed.

This is all done to promote adhesion to the surface you're working on. Imagine basically a thin layer of dust coating the areas to be worked on. If its painted or stained without pressure washing that layer will now be trapped under the surface. If what you're working on is newly built chances are you won't have to pressure wash, but it never hurts. Over time the coating will deteriorate faster because whatever was put on the surface never had a chance to properly bond or adhere to the surface. In the case of fences or decks, pressure washing most importantly removes the mildew and mold. There are plenty of cleaners for mildew and mold that can be bought out there. Another alternative would be bleach.

As you can see this is a crucial step. The goal is to have a surface that's dry, dull but most importantly clean. Having your new paint job last for the long run is the major purpose plain and simple. Next time you are painting or staining a large project make sure to hit it with a pressure washer. Last thing, if you're working on a small area or surface just wipe it down and dust it off, no need to bust out a pressure washer! It's usually the simple steps that make a big difference.