Let’s start with soap, water, bleach, and a brush. It’s pretty easy to do unless it’s a two-story house or any place that’s too hard to reach from the ground or with a 6-foot step ladder. Anything higher than that starts to get very hard to reach. Always wear old clothes that you don’t mind getting paint or bleach. There are many different types of brushes that will screw onto an extension pole so you can reach siding on a second level. Using a mixture of soap, water, and some household bleach before painting exterior siding will clean the siding to and kill any mold and mildew on the siding that’s to be painted. Care should be taken not to scrub the paint off down to the bare wood. If you do then you will have to prime any spots of bare wood.
If you clean the siding with a pressure washer, safety should be first and foremost on your mind. High-pressure water can cause serious injuries. There are cases where people have lost toes fingers and worst by being careless with a pressure washer. Be sure to familiarize yourself with the use of the pressure washer and safety procedures before you began. Pressure washers can be rented at your local rental store for a very reasonable daily rate. You can also purchase pressure washers at most paint stores or home improvement stores. If you will be using a pressure washer for other things around your yard such as cleaning masonry, exterior brick, driveways, and sidewalks then I would certainly consider buying one.
Another method to get the surface clean before you began painting exterior siding is using a 2-gallon garden sprayer and a mixture of bleach and water. Mix together in a 5 gallon bucket 1 part bleach and 4 parts water. Fill sprayer with the mixture and spray an area no larger than you can keep wet and rinse off within 5 minutes. This mixture should kill all the mold and mildew and remove most of the dirt. Use a scrub brush for stubborn areas. Make sure you rinse well-leaving none of the bleach residue on the siding. Continue this prosses until you have the entire house cleaned. After this its time to start painting exterior siding and making your house beautiful and protected again.