For the best chemicals to clean a metal roof, stick to gentle detergents such as dish soap, laundry detergent, or car-wash soap mixed in a diluted solution of ¼ cup of soap to 1 gallon of water. These mild cleansers are safe for most roof finishes but are still strong enough to remove remaining dirt particles. Chemicals like bleach or acids can damage your roof, poison landscaping and grass, and pose a hazard to you and your family. If your roof is very dirty or you think it requires chemical cleaning, call a roof cleaning professional.

There are several telltale signs that your roof needs to be professionally cleaned. It's best to hire a professional as soon as you notice any indicators of wear to preserve your roof's longevity. Key signs to look for include:

• Moss, Algae, or Plant Growth: Look for moss growth, black streaks (which are often a type of black algae), or any other plant life on your roof's surface.

• Dirt and Grime Buildup: A general layer of dirt and grime can accumulate over time.

• Leaf Buildup: An accumulation of leaves, especially in the gutters, is a clear sign.

• Buildup Under Shingles: Dirt and debris can get trapped under the edges of your shingles.

• Shifting Roof Shingles: While this can indicate other problems, it can also be a sign that cleaning and maintenance are overdue.

• Comparison to Neighbors: If your roof appears significantly dirtier or different from your neighbors' roofs, that’s another sign it may be time for a cleaning.

Yes, you can, but you’ll need to acquire the right pressure washer tips and cleaning solutions for the job. In particular, you’ll need tips that are capable of lowering the pressure from a max of 3,500 PSI to between 150 and 300 PSI. As for the cleaning solution, look for options that are clearly marked for soft washing rather than pressure washing. 

Flat roofs are a solid option for people who want extra outdoor space. Flat roofs are very common in other parts of the world and only recently has the U.S. started to see the benefit in the increased space. Flat roofs are also easier to maintain and pose much less of a safety risk, which allows for more DIY work for handy homeowners. Some people also build green or living roofs that grow plant life.