Confronted with unsightly stains or debris on their roofs, many homeowners contemplate pressure washing as a solution. However, it’s important to approach this task with caution. The decision to pressure wash a roof should not be taken lightly, as it can lead to irreversible damage if not done properly. In this blog post, we will discuss the pros and cons of pressure washing a roof, as well as provide valuable insights on when it is appropriate to use this method.

Key Takeaways:

Basics of Pressure Washing

Obviously, before deciding whether it’s okay to pressure wash a roof, it’s important to understand the basics of pressure washing. This includes knowing what pressure washing is, the process of pressure washing, and the types of pressure washers available.

What is Pressure Washing?

Pressure washing is a highly effective method that involves using a machine that pumps water at high pressure through a hose and nozzle to clean surfaces. The force of the water is what helps to remove dirt, grime, and other unwanted substances from the surface being cleaned.

The Process of Pressure Washing

Using pressure washing correctly is essential when cleaning a roof. It’s about choosing the right tools and settings to safely remove dirt and grime without damaging the roof. This method requires a careful approach to protect the roof’s material.

Types of Pressure Washers

There are two main types of pressure washers:

Gas-powered pressure washers are more powerful and are suitable for heavy-duty cleaning tasks, while electric-powered pressure washers are more lightweight and suitable for smaller, less demanding tasks.

Recognizing the differences between these types of pressure washers is important in determining which one is best suited for a specific cleaning task.

Understanding Roof Types

Unlike other exterior surfaces, roofs come in a variety of materials and styles, each with its own unique characteristics and considerations. It is important to understand the type of roof you have before deciding whether or not to pressure wash it.

Roof Type Characteristics
Asphalt Shingles Prone to granule loss from high-pressure washing
Tile Roofs Susceptible to cracking under high pressure
Metal Roofs Can withstand pressure washing with caution
Wooden Shakes Vulnerable to water damage and stripping of natural oils
Slate Roofs Risk of tile displacement or breakage with pressure washing

Asphalt Shingles

Asphalt shingle roofs, the most common type of roofing material in New Zealand, can be seriously damaged by pressure washing. Although it may seem like a quick solution for removing moss and debris, this method can strip away the shingles’ protective granules, significantly shortening their lifespan.

For this reason, it is not recommended to pressure wash asphalt shingle roofs, as the potential for long-term damage far outweighs any short-term aesthetic benefits. Instead, a gentle approach using a soft brush and mild cleaning solution is recommended to maintain the integrity of the shingles.

Tile Roofs

For homes with tile roofs, whether it be clay or concrete tiles, a different approach is needed when it comes to cleaning. They require careful attention due to their delicate nature and potential for cracking under intense pressure.

It is crucial to use low-pressure washing techniques and avoid using abrasive brushes or harsh chemicals that could damage the tiles. Professional roof cleaning services are often recommended for tile roofs to ensure a thorough yet gentle cleaning process that preserves the integrity of the tiles.

Roofs with tile materials require a different level of care compared to asphalt shingle roofs, and understanding the specific needs of each roof type is essential for proper maintenance.

Metal Roofs

An increasingly popular choice for residential and commercial properties, metal roofs offer durability and a sleek modern aesthetic. When it comes to cleaning, metal roofs can withstand pressure washing when done correctly, utilizing low-pressure techniques to prevent damage to the metal panels and protective coatings.

Types of metal roofs, including steel, aluminum, and zinc, have different maintenance requirements and considerations, so it is important to understand the specific material of your metal roof before proceeding with pressure washing or any other cleaning method.

Wooden Shakes

For homes with a more rustic and natural aesthetic, wooden shake roofs provide a charming and distinctive look. However, they require specific care and attention when it comes to cleaning and maintenance. Pressure washing can cause extensive damage to wooden shakes, stripping away their natural oils and accelerating decay.

Plus, it is important to regularly inspect wooden shake roofs for signs of mold, mildew, and rot, addressing any issues promptly to avoid compromising the structural integrity of the roof.

Slate Roofs

Any home with a slate roof exudes a sense of luxury and timeless elegance. These incredibly durable roofs can last for centuries when properly maintained. However, pressure washing is not recommended for slate roofs, as it can dislodge or break the individual slate tiles, compromising the roof’s integrity.

Understanding the specific care and maintenance requirements of slate roofs, including regular inspections and gentle cleaning methods, is crucial to ensure their longevity and visual appeal.

The Risks of Pressure Washing a Roof

Now, let’s delve into the potential risks and hazards associated with pressure washing a roof. While pressure washing can be an effective method for cleaning various outdoor surfaces, it is not suitable for all areas of your home, particularly the roof. When it comes to roof maintenance, the potential damage, water damage and leaks, warranty considerations, and safety concerns that can arise from pressure washing should not be overlooked.

Potential Damage to Roofing Materials

The force of high-pressure water from a pressure washer can dislodge or break roofing materials, such as shingles or tiles. In addition, the use of harsh cleaning chemicals in combination with high pressure can cause further deterioration of the roofing materials. This can result in weakened structural integrity and compromise the protection of your home against the elements.

The potential damage to roofing materials caused by pressure washing can lead to costly repairs and even premature roof replacement. It’s essential to consider gentler methods of cleaning and maintenance to preserve the longevity and functionality of your roof.

Water Damage and Leaks

The force of the water during pressure washing can penetrate under the shingles or tiles, causing water to seep into the underlying structure of the roof. This can result in water damage, as well as the development of leaks inside your home. Over time, these leaks can lead to mold and mildew growth, as well as structural damage.

Rather than risking water damage and leaks by pressure washing your roof, it’s important to prioritize regular roof inspections and maintenance. This proactive approach can help identify and address any potential issues with your roof, ensuring its long-term durability and performance.

Roof maintenance, including periodic inspections and repairs, plays a crucial role in protecting your home from water damage, leaks, and other structural issues. It’s important to prioritize the use of methods that safeguard the integrity of your roof and prevent potential damage.

Warranty Considerations

Leaks caused by pressure washing can also impact the warranty coverage of your roofing materials. Many manufacturers’ warranties explicitly state that damage resulting from improper cleaning methods, including pressure washing, will void the warranty. This means that any potential damage or issues with the roof that arise from pressure washing may not be covered by the warranty, leaving you responsible for the full cost of repairs.

To avoid voiding your roof’s warranty and incurring additional expenses, it’s crucial to adhere to the recommended cleaning and maintenance guidelines provided by the roofing material manufacturer. By following these guidelines, you can help preserve your warranty coverage and protect your investment in your home’s roof.

Safety Concerns

Washing a roof with a pressure washer poses safety hazards for both the person operating the equipment and surrounding individuals. The high-powered water stream can be difficult to control, increasing the risk of injury or accidents. Additionally, using a pressure washer on a sloped surface, such as a roof, can create unstable footing and increase the likelihood of slips and falls.

Water and electricity are a dangerous combination, and using a pressure washer on a roof increases the risk of electrical hazards. It’s important to prioritize safety and consider alternative methods for cleaning and maintaining your roof to minimize the risk of accidents and injuries.

Alternatives to Pressure Washing

Despite the effectiveness of pressure washing, there are alternative methods for cleaning a roof that can be gentler on the roof materials and still deliver excellent results. These alternatives include soft washing, chemical cleaning agents, and manual moss and debris removal.

Soft Washing

Pressure washing can be too harsh for some types of roofing materials, especially those that are older or more delicate. Soft washing is a method that uses gentle, low-pressure water combined with environmentally friendly cleaning solutions to effectively remove dirt, grime, and organic growth from the roof’s surface. This approach ensures thorough cleaning without causing any damage to the roof.

Chemical Cleaning Agents

With advancements in cleaning technology, there are now specialized chemical cleaning agents available that can effectively clean a roof without the need for high-pressure washing. These cleaning agents are designed to break down and remove organic matter, mold, mildew, and algae from the roof’s surface while being safe for the environment and surrounding vegetation. With the right application and a thorough rinse, chemical cleaning agents can restore the roof’s appearance and extend its lifespan.

Cleaning agents, when used properly, can effectively remove stains, dirt, and organic growth from the roof while preserving the integrity of the roofing materials. It’s essential to choose a cleaning agent specifically formulated for roof cleaning and to follow the manufacturer’s instructions for safe and effective use.

Manual Moss and Debris Removal

Soft scrubbing and manually removing moss, leaves, and debris from the roof can be an effective way to maintain its cleanliness without the need for high-pressure washing. This method involves gently brushing or scraping off any visible moss and debris while taking care not to damage the roof’s surface. This approach can be particularly useful for roofs with delicate or aging materials that may not withstand the force of pressure washing.

Any stubborn areas can be treated with a targeted application of cleaning agents or a gentle rinse to ensure thorough cleaning without causing damage to the roof. Manual moss and debris removal is a meticulous yet effective alternative to pressure washing for maintaining the cleanliness and appearance of a roof.

How to Safely Pressure Wash Your Roof (If Applicable)

Not all roof types can withstand the force of a pressure washer, but if your roof is suitable for pressure washing, it’s important to do so carefully to avoid causing damage. Here’s a guide on how to safely pressure wash your roof if it’s applicable to your specific roofing material.

Selecting the Right Pressure Washer

Pressure washing a roof requires a delicate balance of power to effectively remove dirt and grime without causing damage to the shingles or tiles. It’s crucial to select a pressure washer with the appropriate power and nozzle options for your specific roof material. Too much pressure can lead to leaks, broken shingles, or water intrusion, while too little pressure may not effectively clean the roof.

When choosing a pressure washer, consider the PSI (pounds per square inch) and GPM (gallons per minute) ratings, as well as the nozzle tips. For most roofs, a pressure washer with a PSI of 1200 to 1800 and a GPM of 1.4 to 1.6 is suitable. Additionally, using a wide fan tip nozzle (40-degree or higher) can help distribute the pressure evenly and reduce the risk of damage.

Appropriate Pressure Settings

Roof materials such as asphalt shingles, clay tiles, or metal require different pressure settings to ensure effective cleaning without causing harm. It’s important to use low pressure when pressure washing a roof to avoid dislodging granules, cracking tiles, or denting metal. For asphalt shingles, the pressure should generally not exceed 1200 PSI to prevent damage, while clay tiles and metal roofs can withstand slightly higher pressures.

Appropriate pressure settings also involve using the correct nozzle tips to disperse the water evenly across the roof’s surface, preventing concentrated pressure in one area. It’s essential to adjust the pressure and angle of the spray to avoid lifting or damaging the edges of the roofing material.

Protective Measures for Your Roof

Your roof is a crucial part of your home’s structure, and protecting it during the pressure washing process is paramount to avoid costly repairs or replacements. Prior to pressure washing, it’s essential to inspect the roof for any loose or damaged shingles or tiles that may become dislodged during the cleaning. Secure any loose elements and make necessary repairs before proceeding with pressure washing.

This inspection should also include checking for any signs of wear or weakness in the roof structure, such as rot or decay, to ensure that it can withstand the pressure of the washing process. Additionally, protecting surrounding landscaping, covering gutters, and using a mildew and moss inhibitor after cleaning can help maintain the integrity of the roof and prevent future damage.

Step-by-Step Guide

Applicable Roof Types Pressure Settings
Asphalt Shingles 1200 PSI or lower, wide fan tip nozzle
Clay Tiles 1500 PSI or lower, wide fan tip nozzle
Metal Roof 1800 PSI or lower, wide fan tip nozzle

This step-by-step guide details the specific pressure settings and techniques recommended for each roof type, ensuring a safe and effective cleaning process that preserves the integrity of the roof.

Professional Roof Cleaning Services

Your roof is a vital part of your home’s structure and protecting it from the elements is crucial. Professional roof cleaning services can help you maintain the integrity and appearance of your roof, extending its lifespan and preventing costly repairs.

When to Hire a Professional

Cleaning your roof yourself can be dangerous and may result in damage to the shingles or tiles. Additionally, there are certain types of algae, moss, and lichen that require professional treatment to ensure they are fully removed and do not grow back. It is best to hire a professional roof cleaning service if you notice discoloration, streaks, or any signs of organic growth on your roof.

Regular roof maintenance can help prevent the buildup of debris, algae, and moss, thereby extending the life of your roof. Look for a professional roof cleaning service that has experience in dealing with your specific type of roof and offers comprehensive cleaning and maintenance packages.

Look for a company that is licensed, insured, and has a good reputation in the community. It’s important to choose a service that uses eco-friendly cleaning solutions and has the proper equipment to safely and effectively clean your roof without causing any damage.

The Importance of Regular Roof Maintenance

What many homeowners fail to realize is that regular roof maintenance is essential for the long-term health of their roof. By investing in professional roof cleaning services on a regular basis, you can prevent the buildup of debris, algae, and moss, which can lead to costly repairs and premature roof replacement.

Maintenance of your roof can also improve the energy efficiency of your home by keeping your roof in good condition and preventing air leaks. Additionally, regular maintenance can help protect your home’s structural integrity and maintain its curb appeal.

To wrap up

On the whole, pressure washing a roof is not recommended. While it may seem like a quick fix for removing stains and moss, the high pressure can cause damage to the shingles and disrupt the protective layers of the roof. Instead, it is best to use gentler methods such as low-pressure washing or using specialized cleaning solutions specifically designed for roofs. Additionally, regular maintenance and preventative measures like trimming overhanging branches and keeping gutters clean can help prevent the build-up of debris and algae on the roof, prolonging its lifespan and maintaining its appearance.


Q: Is it OK to pressure wash a roof?

A: No, it is not recommended to pressure wash a roof as it can cause damage to the roofing material and lead to leaks.

Q: What could happen if I pressure wash my roof?

A: Pressure washing a roof can strip away the granules on asphalt shingles, break or crack tiles, and force water under the shingles, leading to water damage.

Q: How should I clean my roof instead of pressure washing?

A: It is best to clean a roof using a gentle approach such as low-pressure washing, soft washing, or using a brush and mild cleaning solution to remove algae, moss, or debris.

Q: Can pressure washing void my roof warranty?

A: Yes, pressure washing a roof can potentially void the warranty of the roofing material, as it is often not recommended by manufacturers.

Q: Are there any alternatives to pressure washing for roof maintenance?

A: Yes, alternative methods for roof maintenance include regular inspections, keeping gutters clean, trimming overhanging branches, and using zinc or copper strips to prevent algae and moss growth.