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How to Clean Asphalt Roof: A Comprehensive Guide from Start to Finish

Cleaning an asphalt roof is essential for extending its lifespan, maintaining curb appeal, and preventing costly repairs. While professional cleaning is often the safest and most effective option, homeowners can clean their asphalt roofs themselves with careful preparation, the right tools, and a gentle approach. This article provides a comprehensive guide on how to safely and effectively clean an asphalt roof, ensuring its longevity and protecting your investment.

Why Clean Your Asphalt Roof?

Asphalt roofs, while durable, are susceptible to the growth of algae, moss, and lichen, particularly in humid climates. These organisms not only detract from the aesthetic appeal of your home but can also cause significant damage. Algae, especially Gloeocapsa Magma (often referred to as “roof algae”), feed on the limestone filler in asphalt shingles, weakening their structure over time. Moss and lichen trap moisture, leading to granule loss, rot, and even leaks. Regular cleaning removes these threats, preserving the integrity of your roof and preventing premature degradation. Furthermore, a clean roof reflects sunlight more effectively, potentially reducing energy costs in warmer months.

Assessing Your Roof’s Condition

Before embarking on any cleaning project, a thorough assessment is crucial. Check for loose or damaged shingles, cracked sealant around vents and flashing, and any signs of underlying structural issues. If you identify significant damage, consult a professional roofing contractor before attempting any cleaning. Walking on a damaged roof can exacerbate the problem and pose a safety risk. Also, consider the age of your roof. Older roofs may be more fragile and require an even gentler cleaning approach. Look for areas heavily colonized with algae, moss, or lichen, as these areas will require more focused attention. Note the pitch of your roof; steeper roofs are inherently more dangerous to work on and may necessitate professional assistance.

Safety First: Essential Precautions

Roof cleaning can be hazardous. Prioritize safety above all else.

Wear appropriate safety gear: This includes sturdy, slip-resistant shoes (roofing boots are ideal), safety glasses, and gloves. Consider wearing a safety harness tethered to a secure anchor point if you are uncomfortable working at heights.
Work on a dry day: Avoid cleaning your roof when it’s raining, windy, or excessively hot. Wet surfaces are slippery, and strong winds can make it difficult to maintain your balance. High temperatures can also cause cleaning solutions to dry too quickly, potentially damaging the shingles.
Inform someone: Let a family member or neighbor know that you’ll be on the roof and the estimated time you’ll be working. This ensures someone knows to check on you if anything goes wrong.
Use a ladder safely: Ensure your ladder is securely positioned and extends at least three feet above the roofline. Have someone spot you while you’re climbing up and down.
Avoid high-pressure washers: High-pressure washers can easily damage asphalt shingles by blasting away the protective granules. Never use a pressure washer on an asphalt roof.

Choosing the Right Cleaning Method

The best cleaning method depends on the severity of the infestation and the type of staining.

Soft Washing: The Preferred Method

Soft washing is the most recommended method for cleaning asphalt roofs. It involves using a low-pressure sprayer to apply a cleaning solution that kills algae, moss, and lichen without damaging the shingles. This method minimizes the risk of granule loss and prolongs the life of your roof.

Manual Scrubbing (Use with Extreme Caution)

In some cases, gentle scrubbing with a soft-bristled brush may be necessary to remove stubborn growths. However, exercise extreme caution to avoid damaging the shingles. Never use a stiff-bristled brush or excessive force.

DIY Cleaning Solutions

While commercially available roof cleaning solutions are readily available, you can also create your own. A common DIY solution consists of:

50/50 mix of water and household bleach: This solution is effective at killing algae and moss. However, bleach can be harmful to plants and pets, so take precautions to protect your landscaping. Always test the solution on an inconspicuous area of the roof first to ensure it doesn’t discolor the shingles.

Important Note: When using bleach, avoid mixing it with ammonia or other cleaning products, as this can create toxic fumes.

The Cleaning Process: Step-by-Step

Protect your landscaping: Cover plants and shrubs around the base of your house with plastic sheeting to protect them from cleaning solutions. Wet the plants thoroughly before and after cleaning to further minimize any potential damage.
Apply the cleaning solution: Using a low-pressure sprayer or pump sprayer, apply the cleaning solution evenly to the affected areas of the roof. Allow the solution to dwell for the recommended time (usually 15-20 minutes), but don’t let it dry completely.
Rinse thoroughly: Using a garden hose with a wide nozzle, gently rinse the roof with water. Avoid using a high-pressure nozzle, as this can damage the shingles. Rinse from the top down to avoid driving water under the shingles.
Inspect and repeat: After rinsing, inspect the roof to ensure all algae, moss, and lichen have been removed. If necessary, repeat the cleaning process on stubborn areas.
Clean up: Remove the plastic sheeting from your landscaping and rinse any remaining cleaning solution from the plants. Properly dispose of any used cleaning solutions.

Post-Cleaning Maintenance

After cleaning your roof, consider implementing preventative measures to inhibit future growth.

Install zinc or copper strips: These strips can be installed along the roof ridge and release small amounts of zinc or copper ions each time it rains, preventing the growth of algae and moss.
Trim overhanging branches: Prune trees and shrubs that overhang your roof to improve airflow and reduce moisture retention.
Regular inspections: Inspect your roof regularly for any signs of new growth or damage. Addressing problems early can prevent them from escalating into more serious issues.

FAQs: Addressing Your Concerns

FAQ 1: How often should I clean my asphalt roof?

The frequency of cleaning depends on your climate and the level of tree cover around your home. Generally, cleaning your roof every 1-3 years is recommended, especially in humid or shaded areas.

FAQ 2: Can I walk on my asphalt roof?

Walking on an asphalt roof can be risky, especially if the roof is old or damaged. Minimize walking on the roof as much as possible. If you must walk on the roof, wear soft-soled shoes and step on areas where the shingles overlap.

FAQ 3: What is “roof algae” and how do I get rid of it?

Roof algae, specifically Gloeocapsa Magma, is a black or green algae that thrives in humid environments. It can be effectively removed with a 50/50 mix of water and household bleach, applied using a soft wash technique.

FAQ 4: Will cleaning my roof void the warranty?

Check your roofing warranty carefully. Some warranties may be voided if you use certain cleaning methods or chemicals. Always consult your warranty documents before cleaning your roof. Professional cleaning often avoids this risk.

FAQ 5: What if I can’t reach certain areas of my roof safely?

If you can’t safely reach certain areas of your roof, hire a professional roofing contractor or roof cleaning company. They have the necessary equipment and expertise to clean your roof safely and effectively.

FAQ 6: Is it better to use a commercially available roof cleaner or a DIY solution?

Both commercially available roof cleaners and DIY solutions can be effective. Commercial cleaners are often formulated to be safe for asphalt shingles and may contain additional ingredients to prevent future growth. DIY solutions are more cost-effective but require careful mixing and application. Always read and follow the manufacturer’s instructions when using any cleaning product.

FAQ 7: How do I protect my gutters during roof cleaning?

Flush your gutters before cleaning the roof to remove any debris. Consider covering the downspouts with mesh screens to prevent debris and cleaning solution from entering the drainage system. Rinse the gutters thoroughly after cleaning the roof.

FAQ 8: Can cleaning my roof damage the shingles?

Yes, improper cleaning can damage asphalt shingles. Avoid using high-pressure washers, harsh chemicals, or abrasive scrubbing. Opt for soft washing techniques and gentle cleaning solutions.

FAQ 9: How do I know if I need to replace my roof instead of cleaning it?

If your roof is significantly damaged with missing or severely deteriorated shingles, widespread granule loss, or leaks, cleaning may not be enough. Consult a professional roofing contractor to assess the condition of your roof and determine if replacement is necessary.

FAQ 10: What’s the best time of year to clean my asphalt roof?

The best time of year to clean your roof is during the spring or fall, when temperatures are mild and there’s less risk of extreme heat or cold. Avoid cleaning during the hottest part of the summer or when temperatures are near freezing.

FAQ 11: How long does it take to clean an asphalt roof?

The time it takes to clean an asphalt roof depends on the size of the roof, the severity of the staining, and the cleaning method used. A typical residential roof can take anywhere from a few hours to a full day to clean.

FAQ 12: Is it worth hiring a professional roof cleaning company?

Hiring a professional roof cleaning company offers several advantages. Professionals have the necessary equipment, expertise, and insurance to clean your roof safely and effectively. They can also identify and address any underlying issues that may be contributing to the growth of algae and moss. While it’s more expensive than DIY cleaning, it’s often the safest and most effective option, especially for larger or steeper roofs.