Will Bleach Damage Asphalt Shingles?

Asphalt shingles are a popular roofing material due to their durability and affordability.

However, with time, they are exposed to various elements that can cause wear and tear, leading to the need for maintenance and cleaning.

One common question you might ask is whether using bleach for cleaning will damage your asphalt shingles.

Different two parts of grey bitumen asphalt shingles roof one part overgrown with green moss other clean

Bleach is known for its strong cleaning power, and you might consider using it to remove mold, algae, or other stains from your roof.

But it's crucial to understand that improper use of bleach can potentially harm your asphalt shingles.

When used cautiously and in the correct concentrations, bleach can be a beneficial cleaning agent without causing significant damage to the roofing material.

In this article, we'll explore the effects of bleach on asphalt shingles and discuss tips to protect your roof while cleaning it effectively.

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The Composition of Asphalt Shingles

Asphalt shingles are a popular roofing material for residential buildings in the United States. It covers over 80% of the existing residential building stock in some areas.

Roof shingles on top of the house against blue sky with cloud, dark asphalt tiles on the roof background

Understanding the composition of these shingles can help you make informed decisions about their care, including whether or not bleach can damage them.

Your asphalt shingles consist of three primary layers:

1. Fiberglass Base Mat or Organic Base Mat

The foundation of the shingle provides strength and durability to the overall structure.

Fiberglass mats are often more resistant to moisture and fire, whereas organic mats are made from paper or wood fibers, offering flexibility at low temperatures.

2. Asphalt

This waterproofing layer covers the base mat and is responsible for the shingle's main protective property.

The asphalt coating can vary in thickness and is made of a mixture of bitumen, a petroleum byproduct, and crushed rock or sand that helps all the layers bond together.

3. Granule Surfacing

This top layer provides UV protection and additional weather resistance.

The granule surfacing is composed of crushed minerals or ceramic-coated granules that come in various colors and textures to suit your aesthetic preferences.

As their name suggests, the key ingredient in asphalt shingles is asphalt, which is susceptible to environmental factors like heat and sun exposure.

These factors can cause the asphalt to release air pollutants, especially on hot and sunny days.

Effects of Bleach on Asphalt Shingles

When considering the use of bleach on your asphalt shingles, it's important to understand how the chemical composition of bleach might interact with the materials in the shingles.

In particular, be aware of the potential effects of sodium hypochlorite, the active ingredient in bleach, on the shingles' layers.

Old composite roof with damage

Here are the things that could happen to shingles with bleach misuse.

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Color Fading and Discoloration

Using bleach on your asphalt shingles may result in color fading and discoloration.

While a 75% solution of household bleach can be effective in cleaning your roof, it may cause the shingle color to fade.

To reduce the risk of fading, be sure to dilute the bleach solution properly and follow the recommended application guidelines.

Granule Loss

Asphalt shingles are designed with granules that protect them from harmful ultraviolet (UV) rays and extend their lifespan.

However, using bleach on your shingles can cause these granules to loosen or wash away.

This can lead to a weakened shingle that is less resistant to weathering and the elements.

Shingle Deterioration

The chemical composition of bleach can be harsh on asphalt shingles and may contribute to premature deterioration.

Overexposure to bleach can weaken the shingles, making them more susceptible to damage from the elements.

To avoid this issue, be sure to use the proper bleach concentration and avoid excessive applications.

Can Bleach Harm the Longevity of Asphalt Shingles?

In small concentrations, bleach can be relatively safe to use on asphalt shingles, particularly when trying to remove algae, mold, or mildew.

However, using excessive amounts of bleach or applying concentrated bleach directly onto the shingles can cause damage.


To protect your shingles and roof integrity, it's always a good idea to dilute bleach with water.

Generally, a mixture containing 5.25% sodium hypochlorite is found to be effective for disinfecting purposes.

A ratio of one part bleach to three or four parts water should also be sufficient for most cleaning purposes. Although other sources say a 50:50 solution can also be used.

Additionally, using a gentle, low-pressure rinse when applying the solution can help prevent extensive wear and tear on your shingles.

Bear in mind that while bleach can be effective at killing organic growth, it won't prevent regrowth.

To address the root cause of the problem, consider a long-term solution, such as installing zinc or copper strips at the roof peaks, which release natural ions that help prevent algae, moss, and mildew growth.

Check these zinc metal strips for roofs on Amazon.

Alternatives to Bleach for Cleaning Shingles

There are alternative methods for cleaning shingles without the potential negative impacts of bleach.

These alternatives can be both effective and gentle on your asphalt shingles. Let's explore a couple of options: oxygen-based cleaners and eco-friendly products.

Learn more: 11 Roof Shingles Color Ideas And Options

Oxygen-Based Cleaners

Oxygen-based cleaners, such as oxygen bleach or sodium percarbonate, are a less-harsh option for cleaning your shingles.

These cleaners can help remove dirt, algae, and mildew without causing damage to your asphalt shingles.

Check out this chlorine-free oxygen-based cleaner on Amazon.

To use an oxygen-based cleaner, simply mix the powder with water to form a solution.

Apply the solution to your shingles using a low-pressure sprayer, and let it sit for about 15 to 20 minutes. Gently rinse off the solution with a garden hose or low-pressure washer.

This process can safely and effectively clean your shingles, while also limiting any environmental impact.

Eco-Friendly Products

Another option to consider for cleaning your shingles is to use eco-friendly cleaning products specifically designed for use on roofs.

These products are often made from natural ingredients and are free of harsh chemicals that can harm your shingles or the environment.

Some eco-friendly roof cleaning products include:

  • Green algae and moss removers
  • Vinegar and water mixture
  • Baking soda solutions

To use these products, follow the manufacturer's instructions for mixing and application.

Typically, you'll spray the cleaning solution onto the shingles and allow it to sit for a specified time before gently rinsing the shingles with water.

Friendly Reminder to Handle These Chemicals with Care

Before you start, make sure to wear gloves and gather the necessary measuring devices.

blue latex gloves and apron opening a yellow bottle of bleach

It's important to remember that when using a bleach solution, you should first clean the roof surface to remove any superficial dirt or grime.

Applying bleach on a clean surface will enhance its effectiveness and provide a proper level of disinfection.

While working with bleach, be cautious about the risks associated with its vapors, as they may cause irritation to the skin, eyes, or respiratory tract.

Work in a well-ventilated area, wear protective gear, and avoid mixing bleach with incompatible chemicals, as they can produce toxic gases.

If you're uncertain about using bleach on your asphalt shingles or feel unsure about the cleaning process, it's best to consult a professional roofing contractor for advice.

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