Dish Detergent

• Amazingly, a simple solution of water and liquid dish detergent will break up mold and mildew that has formed on the roof, without harming the home and surrounding soil. In a bucket, mix 10 drops of liquid dish detergent per 1 gallon of water. Stream the solution through a hose with a spray bottle attachment. Most times, this will break up any mold and mildew that has not completely set into the roof.
  
  

Bleach

• Bleach works effectively to kill mold spores and get rid of mildew. It is important to first rinse any vegetation on the ground with clear water, as this will work as a barrier between plants and the bleach solution. Mix a solution of one part water, one part bleach. Then, either scrub the roof with this solution, or use a hand-pump sprayer to cover the area. The sprayer will save you the hassle of climbing onto the rooftop. When all mold and mildew is gone, rinse the roof, siding and nearby vegetation with clear water to remove any bleach or mildew residue.
  
  

Copper Sulfate

• A copper sulfate solution also works effectively in removing mold and mildew on the roof. Mix 12 ounces of copper sulfate (available at most hardware and home-improvement stores) per 1 gallon of water. Scrub this solution directly onto the mold and mildewed areas, or run through a hose attachment. Repeat as necessary until all signs of mold and mildew have been removed. Then, rinse the roof and surrounding areas with a stream of clean water to release any leftover mildew or cleaning-solution residue.