If your roof has not been cleaned in a while, it is probably in sad shape — but luckily for you, you can pressure wash roof dirt, grime, and mildew away using a pressure washer. Pressure washers use a stream of warm water under high pressure combined with a cleaning agent to quickly and efficiently clean a wide variety of surfaces. Because your roof is designed to resist and drain away water, a pressure washer is a perfect way to clean it. What follows should give you an idea of what to expect when you pressure wash your roof.
Step 1 - Setting Up
Your setup will depend on the particular pressure washer you use. Before doing anything, read the owner's manual that goes with your pressure washer — doing this will help you plan your setup. However, in general, you will need two things — a water source and a power source. Some pressure washers are gas powered, and some are powered by electricity. Figure out which power source your pressure washer uses and make sure it is available. Additionally, make sure you are in range of a water source.
Once you have verified that you can operate your pressure washer, you need to figure out what chemical solution to use. This is easier than it seems. Anywhere that sells or rents pressure washers will be able to direct you to a mixture that will work with your washer and roof. For cleaning a roof, try to avoid a chemical solution that contains bleach, as it can stain your home and kill plants. If you must use a chemical solution, set up tarps to keep it off of anything that could be damaged.
Since you are setting up, take this time to put your mixture of choice in your pressure washer as directed by its instructions.
Finally, before starting up your pressure washer, you need to wear eye protection and gloves.
Step 2 - Cleaning
Before you begin, tighten all connections in your pressure washer. You do not want any leaks, either in or out.
You should be able to reach your roof with your pressure washer without using a ladder by spraying with a special attachment. Ideally, you should hold your attachment several feet from your roof. Additionally, do not point your pressure washer attachment directly at your roof. Holding it an angle is better. About 45 degrees is the best angle possible to use your pressure washer attachment on your roof.
Keep in mind that pressure washers have their name for a reason — they can produce a great deal of pressure. There are many safety concerns that result from this. Do not aim a pressure washer at yourself or another person. Do not even put your hand in front of it to test the pressure. Serious injuries can result. Additionally, do not use a pressure washer while on a ladder.
Step 3 - Finishing Up
Once you have gone over your whole roof to your satisfaction, wait 10 minutes for the chemical solution to do its work. Once you have done this, go over your roof one more time to rinse it away.