The less expensive solution is to spray wash the roof with a 50 percent mix of water and bleach to get rid of the algae.
Remove mildew from roof shingles.
Allow the oxygen bleach to sit on the shingles for 20 minutes.
In a two gallon bucket create a cleanser composed of 1 4 chlorine bleach and 3 4 water.
Fill a handheld pump sprayer with the solution and apply it to the moldy shingles only.
Rinse from the top of the roof down to avoid re staining the shingles with the dirty water.
They re likely to damage the shingles just be sure to wet your foundation plantings first and rinse everything in clean water when you re done.
Never use a.
Set the nozzle at the highest pressure setting and hold it 12 inches from the shingles.
Allow the solution to soak into the shingles for at least 15 minutes.
But outdoor heavy duty cleaning usually calls for more heavy duty mixtures such as tsp and chlorine bleach see the tsp page for more details or specialty additives such as jomax from rustoleum which combines a cleaner with a bleach activator.
No pressure washers please.
Step 4 take precautions.
Cleaning step 2 make and apply the bleach solution.
Put on rubber gloves and a breathing mask before proceeding you so you can.
Spray all the plants growing near your house with water and this will help protect them from any damage caused by the chlorine bleach.
Step 3 check for cleanliness and rinse.
If you ve had experience with mold and mildew in the home you know the best mildew remover is chlorine bleach.