How to Paint a Metal Roof
To paint a metal roof, you'll need to use an oil-based paint if you have a terne metal roof or an acrylic-based paint if you have a galvanized metal roof. If you're not sure what kind of roof you have, ask a professional roofer to inspect it before you paint it. You'll also need to purchase a primer designed for metal roofs. Once you start working with the roof, use an extension ladder instead of getting on the roof whenever possible. You'll need to prepare the roof by scraping away loose paint and rust with a paint scraper or putty knife. Then, plan on washing the roof with a power washer so it's clean when you apply the paint. You'll then apply one coat of primer and two coats of paint to your roof, although you may need to apply additional coats of paint depending on how dark and rich you want the color to be.
Check with your homeowner’s association for any painting regulations. Some homeowner's associations have rules about what kinds of colors can be used to paint houses. If your neighborhood has a homeowner's association, speak with a representative to find out if there are any restrictions you need to know about before you get started. Choose a paint that’s right for your metal roof. Some historical homes have terne metal roofs, and these need to be painted with oil-based paint. Galvanized metal roofs are usually painted with acrylic-based paint. Find either oil-based or acrylic-based paint at your local home improvement store. To ensure that you know what kind of metal your roof is made out of and what kind of paint you should use, ask a professional roofer to inspect your home. Choose a color that goes with the rest of your house. Try to avoid making your roof the same color as the sides of your house. Instead, choose a neutral color that complements the sides, or a lighter color that gives an accent to your home. If your house is made of brick or stone, it is especially important to make sure your roof complements these materials, as their colors cannot be changed. Purchase a primer designed for metal roofs. You can find primers for metal at your local home improvement store. Ask an employee for help if you're having trouble finding the kind you need. These primers are specifically made to inhibit rust from growing on your metal roof. Work from an extension ladder instead of going on the roof if possible. It's usually safer to work from a ladder instead of on the roof. Lean the ladder against your house. Keep the ladder away from power lines. Do not place the ladder in front of any doors, as someone opening a door could knock the ladder down. Always keep both feet firmly against a rung of the ladder, and hold onto the side of the ladder with the hand you're not working with. When painting from your ladder, don't try to extend your reach to paint areas that are too far away. This could cause you to lose your balance and fall. Instead, use a paint roller with a long handle to reach patches far away from you. Wear a harness with a safety rope when you’re on the roof. Purchase a harness and rope at your local home improvement store. Anchor the rope securely to a stable part of your house or to a tree. Put on the harness and then attach the rope to it. With a harness, you can prevent yourself from falling off of the roof if you lose your balance. Work with a friend to stay safe. Safety is very important when working from on your roof, so it's best to have someone else with you at all times. Have someone hold the ladder from below to keep it stable while you're working from it. This same friend can help you if you do have an accident. Use a paint scraper or a putty knife to scrape away loose paint. Press the scraper or knife firmly against the paint, but make sure you don't damage the metal underneath. Don't worry about patches where the paint is in good shape, as you can simply paint over those. To help the primer and paint adhere to the roof better, try lightly scuffing the surface of the metal. For instance, if you're painting a smaller roof, you might use 80-120 grit sandpaper or a wire brush.  Remove patches of rust if you find them. As you scrape away old paint, you'll get a close look at your entire roof. Old metal roofs sometimes have patches of rust. Try scraping them away with a putty knife if they're small. Try using vinegar or other solutions you can make at home for more stubborn rust. Wash the roof with a  power washer. A power washer will be able to remove any areas of peeling paint you might have missed. It will also clean the roof, preparing it for the next coat of paint. Rent a power washer from a local home improvement store. Spray down your entire roof, moving the wand side to side to catch the whole surface. If you can't get a power washer, use your garden hose on the strongest setting. It is not as effective, but it can still clean the roof. Wait at least an hour for the roof to dry. How long it will take your roof to dry completely depends on the temperature and how sunny it is. Check the last area you washed after an hour. If it's still wet, check again every 15 minutes or so. The roof needs to be completely dry before you move forward. Choose a day with good weather. Avoid painting in the rain, as this could wash your paint away. If possible, try to paint in the spring or fall. Metal roofs can get extremely hot in the summer, making them very difficult to work with. Apply a coat of primer to the entire roof. Use a paintbrush or a paint roller to spread the primer. You need only one coat, but it should be a thick coat. Work from your ladder whenever possible. Carefully go onto your roof for areas that are hard to reach from the ladder. Purchase a roller with a long handle from a home improvement store. This allows you to reach further from your ladder. Wait at least an hour for the primer to dry. The weather can affect how long primer takes to dry, but it will usually take at least an hour. Check the can for your specific primer to see how long it typically takes to dry. When checking to see if the primer is dry, always check the area where you applied it last. Apply a coat of paint to the entire roof. Wash the brush or roller you used for the primer, or get a new one. Apply a generous amount of paint across the entire roof. Again, work from your ladder as much as possible. Wait at least an hour for the paint to dry. Check your can of paint to see how long it generally takes to dry. In most cases, it will take around an hour or so. Apply at least one additional coat of paint. The paint helps protect your roof, so apply it generously. When applying your additional coat, try working from different positions than you did for the first coat. This might help you hit spots you missed before. After the second coat, your roof should be well protected and have a nice color. If the color doesn't seem dark or rich enough yet, apply an additional coat. Always wait for the previous coat to dry before adding a new one. 
Check with your homeowner’s association for any painting regulations. Choose a paint that’s right for your metal roof. Choose a color that goes with the rest of your house. Purchase a primer designed for metal roofs. Work from an extension ladder instead of going on the roof if possible. Wear a harness with a safety rope when you’re on the roof. Work with a friend to stay safe. Use a paint scraper or a putty knife to scrape away loose paint.  Remove patches of rust if you find them. Wash the roof with a  power washer. Wait at least an hour for the roof to dry. Choose a day with good weather. Apply a coat of primer to the entire roof. Wait at least an hour for the primer to dry. Apply a coat of paint to the entire roof. Wait at least an hour for the paint to dry. Apply at least one additional coat of paint. 