Aluminum siding is considered maintenance free, especially when compared to wood siding, which it first replaced. However, aluminum siding still gets dirty, stained with bird droppings, and sometimes mold can form. You may also start to notice a chalky look to your siding from natural weathering. Fortunately, the average homeowner can clean his own aluminum siding. When finished, aluminum siding can be painted, if desired.
The best way to clean your aluminum siding is to get out your power washer. Use just plain water. It will work best If you have access to hot water or if your power washer heats up water; however, cold water will suffice. Start power washing at the top of the siding and work your way down. If you find using the low setting is not sufficient, try the higher setting, but test in an inconspicuous spot first as high pressure washers can sometimes break or bend aluminum siding. Again, start from the top and work your way down to the bottom. Power washing will usually clean most aluminum sidings to the owner's satisfaction.
If the power washing did not do the trick in getting your aluminum siding clean, the next best way to clean it is by using detergent and a soft nylon scrubbing brush. Trisodium phosphate (TSP) or a biodegradable laundry detergent will work well mixed with warm to hot water. Carefully follow dosing directions for the TSP and be sure to wear protective eye wear and gloves. For the biodegradable laundry detergent, mix 1/3 of a cup with 6 gallons of water. Then, carefully scrub your aluminum siding clean. Start at the top and work your way down. Rinse areas clean with your regular hose before they dry.