The proper steps when painting a house are washing, scraping, sanding, repairing, priming, and then finally applying the finish topcoat of house paint. No matter how good the quality of the paint is, you cannot expect it to adhere to old, dirty, peeling paint. Paint must have a stable base.
First, wash the walls to remove dirt, grease, and extremely loose paint chips. If you use a pressure washer to clean the walls, you must be careful because a pressure washer can do considerable damage. If a powerful stream of water is shot directly at the siding, it can force water into it and up under the siding. This is particularly true for two-story homes, when you are directing the water stream up from the ground.
It is better to use the pressure washer on a low-power stream to distribute the cleaner over the walls and to later rinse them with fresh water. A solution of water, trisodium phosphate, and bleach (to kill mildew) is most effective. You must cover any vegetation near the house.
Before you begin, you should totally saturate the ground near the house with water to dilute any solution that runs off. Environmentally safe cleaners are also available, and I recommend them.
Once the cleaning solution is on the walls, give it time to work. It is best to do this washing in the early morning or late evening, when there is no direct sun and less wind, so it will not dry quickly. Use the pressure washer on low power again to rinse the walls with fresh water.
When the walls are dry, it is time to start the scraping. There are several scraping options: hand scraper, power scraper, chemical strippers, and heat strippers. Hand scraping is the most work, but it is still the most effective method to remove layers of old, deteriorating paint.
A good-quality hand scraper will have a handle and a tall knob. It is designed to be a two-handed operation. Always pull the scraper toward your body. This provides more force and less chance it will dig into the wood and damage it. Select a scraper with a hard carbide blade instead of an inexpensive mild steel blade. The steel blades will dull quickly, making the job more difficult and increasing the possibility of damaging the wood.
Once you have all the loose paint removed, sand the surface. This serves two purposes. First, it provides a slightly roughened surface to which the primer can better adhere. Second, it will feather the edges along the spots where the old paint has peeled off. Repair any bad spots with wood repair materials or even automobile body filler. Paint the surface with a good primer selected for the type of topcoat paint you will use.
