Bleach is one of the readily available items that can introduce a new perspective in your roof shingles cleaning routine. When correctly in the right amount, bleach can efficiently destroy the algae, bacteria, mold, mildew, moss, fungus and other organic organisms growing on the roof.

The reason many homeowners and pro roof cleaners use it is that works fast. However, when not properly used with other solutions, it can be dangerous not only to the roof but also to the surrounding environment. Read on for details of using bleach to clean roof shingles, asphalt, and other types of roof systems.

Why is Bleach a Good Roof Cleaner

Bleach is a class of compounds widely used to whiten clothes and remove stains and as a disinfectant to kill germs.

House hold bleach-ingredients for roof cleaning
Clorox Bleach

Liquid household bleach has 5.25 to 8.25% of the active sodium hypochlorite (NaClO) ingredient. It also contains other secondary ingredients such as sodium hydroxide which is intended to keep the solution alkaline.

It is the sodium hypochlorite in bleach that denatures proteins in microorganisms that thrive on roofs. This ingredient is effective in killing algae, mildew, mold, fungi, bacteria, and viruses.

The Sodium hypochlorite becomes hypochlorous acid when it comes into contact with water.  Hypochlorous acid is the active ingredient further that attacks proteins that make up the microorganisms leading to the destruction of the algea as well as other microorganisms on your roof shingles.

How to use Bleach to Clean Roof Shingles

Using bleach is a fast and efficient way of cleaning and keeping your roof shingles clean. It can be is used to clean stained and dirty roof shingles.

Some of the items you will need for the method below include water, chlorine bleach, 1 cup of powdered laundry soap, a stiff roof broom/brush, ladder pump garden sprayer, a large bucket, a ladder, gloves, apron, goggles and rubber soled shoes with good gripping.


Bleach irritates mucous membranes, the skin and the respiratory system. Do not forget to put on protective gear; gloves, lab coat or plastic apron, and goggles

Bleach reacts readily with other chemicals, so caution should be exercised when using this chemical. Ensure the area is well ventilated when diluting or using bleach.

Cold water should be used for dilution as hot water decomposes the active ingredient, sodium hypochlorite, rendering it ineffective.

Cleaning procedure for roof shingles with bleach, powdered laundry soap and water

  1. Use a ladder to climb and inspect the roof for dirt, algae, mold, mildew, moss or lichen.
  2. After identifying the affected areas climb down the roof and mix thoroughly 1 gallon of hot water, 1 cup of chlorine and 1 cup of powdered laundry soap in a large bucket.
  3. Pour the mixed solution into a garden sprayer.
  4. Carefully get to the roof using a ladder and spray the affected shingles; starting from bottom to the top of your roof.
  5. You also gently scrub the wet areas as you spray the solution on dry areas.
  6. Rinse the roof.
  7. Repeat the process until when the roof shingles are clean.

Cleaning asphalt roof shingles with bleach and water

Bleach and water work well when cleaning asphalt roof shingles. Clean the roof following the procedure below;

  1. Climb the roof using a ladder and inspect the roof to find areas affected with algae, stains or moss.
  2. Wet all the plants and vegetation around your home to protect them from bleach mixture.
  3. Mix equal parts of bleach and water in the ratio of 50:50 to form a bleach cleaning solution.
  4. Pour the solution in a garden hose sprayer.
  5. Climb the roof using a ladder and spray the shingles with the solution.
  6. Leave the solution on the surface of the roof shingles for 15 to 20 minutes.
  7. Rinse thoroughly with water. Any remaining algae or moss will be washed away with rain or blown away by wind.

When using this method ensure that you clean the roof in the morning hours or when it’s cloudy and there is no rain. If you clean on a sunny day bleach will evaporate. Keep repeating the process till the roof is clean. If the problem of algae and moss persists then it is important to consult a professional roof cleaner.

How to use Bleach to clean other types of roofs

Some types of bleach for instance oxygen bleach, can be used to clean other types of roofs. It is environment friendly and it does not damage the color of the roof on wooden roof shingle shakes. This procedure requires the bleach and water

  1. Inspect it for algae, moss, mold, mildew, dirt and stains.
  2. Dilute a solution of oxygen bleach with water and pour the solution in  a pump sprayer,
  3. Use a ladder to climb the roof and wet the whole roof with plain water using a garden hose.
  4. Spray the affected areas of your roof.
  5. Leave the solution on the roof for 15 minutes.
  6. Use a garden hose to rinse the roof with water.
  7. Repeat the same process until you get all the stains off the roof.

Cleaning the roof with bleach and Trisodium phosphate

The benefit of using Trisodium Phosphate is that it comes with sodium hypochlorite as the active ingredient. Cleaning your shingles with this solution requires; a pressure washer with black soft spray chemical injector tip, 5.5 gallon system and hot water

  1. Start by climbing the roof using a ladder to inspect affected areas.
  2. Wear gloves, goggles and rubber soled shoes
  3. Wet all the plants and vegetation around your home to protect them from bleach mixture.
  4. Pour a ratio of 50: 75 Trisodium Phosphate and bleach into the mixing tank a for 1500-2000 square roof affected by algae.
  5. Use a pressure washer with a black soft spray chemical injection to add water in the tank.
  6. Stir the solution with the spray tip as you add water and leave it to settle for 5 to 10 minutes.
  7. Spray the solution on the roof and leave it for 30 minutes.
  8. Rinse the roof with water.
  9. Water exterior surfaces of the building, windows and plants after cleaning.

The disadvantage of this is that trisodium phosphate strips paint from the roof. If the solution is left on windows, it dries leaving tough stains that are difficult to remove. It also contains phosphates that are harmful to the environment.

How much Bleach is safe for your Roof?

When using bleach, the amount you use is a key factor that will determine the results. According to ARMA (Asphalt Roofing Manufacturers Association) a 50/50 solution of household strength sodium hypochlorite  and water is sufficient to remove moss and algae. Below is a discussion from a roof cleaning expert explaining how much sodium hypochlorite is too much to damage your roof.

Benefits of using Bleach for Roof Cleaning

Bleach is readily available and one of the fastest ways of cleaning algae from the roof and shingles.  It is a strong cleaner that kills algae and fungus and removes stains that comes with it. It makes it easy to get rid of dirt on the roof and shingles.

 There is no need of rinsing or inspecting the roof after the application.

Oxygen bleach is recommended because it does not harm plants and animals in the environment. It saves time and energy because there is no need of watering plants and vegetation before cleaning the roof with bleach.


Following are reasons beach can be bad cleaning agent for your roof

  • Trisodioum phosphate bleach causes eye damage. It also irritates and burns skin depending on its concentration when used without taking precaution.
  • It dries out shingles thus they curl, crack and have a short life span if not used according to the instructions of the roof manufacturer.
  • It degrades wood and it is also toxic depending on the type of roof where it is applied.
  • Patients with lung diseases are affected by fumes from bleach which may accelerate the disease. Sodium hypochlorite reacts with light and produces dangerous chlorine gas.
  • It is corrosive when used in high concentrations thus it may corrode flashing, valleys and boots other than the roof it cleans the surface but it does not penetrate the roof to remove the roots of black mold.


Always keepbleach away from children and wear safety glasses and gloves every time when using it.

You must go an extra mile to water; plants, shrubs and vegetation to prevent phosphates in bleach from hurting the environment.

Before using bleach to clean your roofs at home, be sure to equip yourself with enough knowledge and do follow the manufacturer’s instructions on the bleach product. If you can, involve a roof cleaning professional. 



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