For those tough spots use a gentle.
How to remove algae from aluminum siding.
How to clean algae off of aluminum siding.
Wash the whole house with a mix of common laundry detergent and water through a presser washer once a year.
Stains on wood cleanse with mild detergent mixed with water.
If mold or mildew is the culprit spraying with a bleach solution will remove it.
Spray this mixture on remaining spots.
To 1 quart and use it in the same power washer as step 1.
Mildew and algae on vinyl and wood use a solution made of oxygen bleach not chlorine bleach mixed with water.
Create a mix of bleach and water 1 tsp.
To clean aluminum siding having mildew use a solution of one part bleach and four parts water.