Mold can grow on aluminum siding when the area is exposed to water or humidity and receives a limited amount of sunlight. Mold is a fungus that attaches itself to surfaces and can be a health hazard. Remove the mold as soon as you notice it to prevent it from spreading, and keep in mind that removing mold from aluminum siding may require more than one attempt.
Close the windows on the side of the house where you will be cleaning. Cover any shrubs of plants near the house with tarps. Cut back or prune any plants that are touching the house. Remove any debris against the wall. Cut back any tree branches that are shading the house and preventing sunlight from shining on the wall. Mold cannot thrive in sunlight.
Hose down the side of the house with a garden hose on its strongest setting. Rinse off as much of the mold as possible. Remove stubborn mold with a power washer, making sure the jet stream is not so powerful that it damages the aluminum siding.
Scrape off any visible remaining mold with a spatula. Make sure it is a non-metallic spatula in order to avoid scratching the aluminum siding.
Prepare a solution of one part bleach to four parts water in a bucket. A household bleach product can be used and is less expensive than many commercial products. Bleach kills mold spores.
Clean the aluminum siding with a sponge dipped in the water/bleach solution. Scrub as hard as possible without buckling the aluminum.
Rinse off the siding with a hose and water. Allow the siding to dry and inspect it again to see if any mold remains.
Use a spray bottle to apply the beach/water solution to any remaining mold spots. Scrub the spots with a sponge. Rise the siding, allow it to dry and inspect it again.
Attack the mold with a commercial mold-cleaning product if the mold persists or quickly comes back. These products are available at hardware stores.
Scoop up any mold on the ground and place it in garbage bags. Dispose of the garbage bags as soon as possible.