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May 7, 2024

Is it OK to Pressure Wash a Roof?

Yes, it is ok to pressure wash a roof, but only if you have done in-detail research work before. You have to assess the condition of the roof, read the manufacturer’s guidelines, and procure the necessary safety equipment. When done correctly, pressure washing is effective on many types of roofing materials.

It’s ok to pressure wash a roof. But why?

It’s ok to pressure wash a roof for several reasons, but you need to do due diligence before proceeding. Pressure washing uses a high-pressure water stream to remove dirt, debris, stains, and contaminants from many surfaces. It uses specialized treatment such as a pressure washer that pressurizes water to create a strong jet that dislodges and washes away difficult grime.

Why it’s ok to pressure wash a roof

  • It removes dirt and debris

The high-pressure water stream from the pressure washer will efficiently dislodge and remove dirt, dust, leaves, and debris from surfaces. It gets deep into crevices and difficult-to-reach areas to ensure thorough cleaning.

  • It removes stains

Pressure washing can remove difficult stains such as algae, mildew, and moss from the roof’s surface. The force of the water stream breaks down lifts stains and gives the roof its initial appearance.

  • It’s versatile

Pressure washing is adequate for many roofing materials.

  • It’s effective

Pressure washing works fast and can cover large areas in a short amount of time.

  • It works as preventive maintenance

Regular pressure washing reduces the risk of buildup of dirt, grime, and organic growth on surfaces. It expands the roof’s lifespan and reduces the need for repair work.

What surfaces can be cleaned with pressure washing

The surfaces that can be cleaned with pressure washing are many:

  • Concrete surfaces

Pressure washing is highly efficient for cleaning concrete surfaces such as sidewalks, driveways, patios, and retaining walls.

  • Brick and masonry

Brick and masonry surfaces on buildings, walls, and facades can accumulate dirt, moss, effloresce, and mildew. Pressure washing efficiently removes the contaminants. Professionals take care when pressure washing brick surfaces to avoid damage to surface and mortar joints.

  • Wooden surfaces

Decks, fences, and siding made of wood can be cleaned from mould, mildew, algae, and dirt buildup with pressure washing. Professionals use lower pressure settings and adequate cleaning solutions to avoid damage.

  • Vinyl siding

Proper technique and distance are used when pressure washing the vinyl siding on homes and buildings. This way, it can be avoided warping, cracking, and discolouration.

  • Metal surfaces

Pressure washing is efficient at cleaning metal surfaces such as aluminium, steel, and wrought iron.

Is pressure washing suitable for all roofing materials

No, pressure washing isn’t suitable for all roofing materials. Here’s an overview:

Clay tiles

Clay tile roofs are durable and can withstand the forces of pressure washing. Pressure washing removes dirt, stains, algae, and moss from clay tiles and revitalizes their colour and appearance.

Slate roofs

Slate roofs are dense and non-porous and can be cleaned with pressure washing.

Synthetic roofing materials

Some synthetic roofing materials, such as composite tiles and synthetic shingles resemble natural materials. However, they are durable and resist pressure washing.

Asphalt shingles

Pressure washing isn’t the most adequate cleaning method for asphalt shingle roofs. Asphalt shingles are made of granules adhered to fibreglass or organic mat base. High-pressure water can dislodge the granules and cause premature degradation of the shingles.


Soft washing and manual cleaning with gentle scrubbing and mild detergents can be used to clean roofs made of asphalt shingles.

Metal roofs

Metal roofs such as those made of aluminium, steel, or copper can be cleaned with pressure washing. It’s because they have a non-porous nature.


Adequate pressure settings have to be used. It’s also necessary to avoid directing the water stream at seams, flashing, and areas with a risk of water penetration (seams, flashing).

Concrete tiles

Pressure washing is safe to use on concrete tiles to efficiently remove dirt, moss, algae, and contaminants from concrete tiles.

Wood shakes

Pressure washing isn’t recommended on wood shake roofs as wood shakes are made of natural wood. Natural wood is porous and sensible to damage from high-pressure water.

Alternative methods

Manual cleaning with gentle scrubbing and specialised wood cleaners or chemical treatments is more appropriate for cleaning wood-shake roofs.

Risks associated with pressure washing delicate roofing materials

  • Damage to surface

Delicate roofing materials can be damaged by high-pressure water. The force of the water stream may dislodge granules from shingles and cause premature degradation, splint wood shakes, and lead to structural damage.

  • Water intrusion

When incorrectly used, high-pressure water can go beneath roofing materials, such as shingles or tiles. Water may penetrate the underlying structure and cause leaks, rot, and damage to the roof deck and building’s interior.

  • Destroy protective coating

Some roofing materials have protective coatings or finishes that pressure washing may destroy. The force of the water stream may wear the coatings, and reduce the efficiency in protecting the surface from UV rays, moisture, and environmental damage.

  • Risk of mould and mildew growth

Incorrect or incomplete pressure washing methods may leave organic matter or moisture. They make for an ideal environment for mould and mildew growth.

The benefits and disadvantages of pressure washing

The benefits of pressure washing

  • Ensures efficient cleaning

Pressure washing efficiently removes dirt, debris, algae, moss, mildew and other contaminants from the roof’s surface. The high-pressure water stream goes deep into crevices, ensures thorough cleaning, and restores the roof’s initial appearance.

  • Improves curb appeal

A clean roof improves the curb appeal of a property. Pressure washing removes unsightly stains and discolouration and gives the roof a fresh look.

  • Expands the roof’s lifespan

Regular pressure washing expands the roof’s lifespan as it prevents the buildup of dirt, debris, and organic growth. The risk of damage and degradation is reduced and the roofing materials will last longer.

  • Prevents damage

In time, dirt, algae, moss, and other contaminants may deposit on the roof’s surface and cause degradation. Pressure washing removes harmful substances, and lowers the risk of premature wear and tear. It also lowers the need for expensive repair or premature roof replacement.

  • Maintains property value

A clean and well-maintained roof contributes to the property’s value. Pressure washing preserves the roof’s condition, protects your investment, and ensures that your property keeps its value in time.

  • Improves energy efficiency

A clean roof reflects more sunlight and heat than a dirty one. It absorbs less heat and maintains the inside temperatures cool and comfortable in the summer. The need and costs for cooling will significantly decrease.

  • Prevents pest infestations

Organic growths such as algae, moss, and mildew attract pests such as insects and rodents. Pressure washing removes the growths, reduces the risk of pest infestations, and protects the roof’s integrity.

  • Benefits the health

Algae, mould, and mildew on the roof pose health risks to people inside because they release spores into the air. Pressure washing removes the contaminants and creates a healthy environment. It also improves indoor air quality.

The disadvantages of pressure washing

  • Risk of damage

High-pressure water may damage delicate roofing materials such as asphalt shingles or wood shakes.

  • Water intrusion

Incorrect pressure washing techniques or excessive water pressure can push water beneath roofing materials and cause water intrusion. Leaks, rot, and damage to the roof deck and inside of the building will occur.

  • Destroy protective coatings

Some roofing materials have protective coatings or finishes that pressure washing may destroy. The force of the water stream can wear away the coatings and reduce their efficiency in protecting the surface from moisture, UV rays, and environmental damage.

  • Risk of mould and mildew growth

Incomplete or incorrect pressure washing methods can leave moisture or organic matter and create a favourable environment for mould and mildew growth.

  • Safety concerns

Working on a roof can be dangerous, especially when using the pressure washer at heights. Uneven surfaces, slippery surfaces, and electrical hazards pose risks of injuries, falls, and accidents.

  • Environmental impact

Pressure washing may result in the runoff of water, cleaning solutions, and contaminants into the environment. The runoff may pollute waterways, and harm plants, and wildlife.

  • Limited efficiency on difficult stains

Even if pressure washing efficiently removes most dirt, debris, and stains, it’s not enough for difficult stains or deeply embedded grime. In such scenarios, additional cleaning methods or treatments will be needed.

  • High costs

Pressure washing can be expensive, especially for large roofs or heavily soiled roofs.

What to consider before pressure washing the roof

Before pressure washing the roof, you need to consider several aspects:

Assess the condition of the roof

Before pressure washing the roof, you have to examine the roof’s condition to detect damage, degradation, and areas of concern. You have to inspect for loose or missing shingles, signs of water damage, structural problems, and cracks.

Assessing the roof condition helps you decide if pressure washing is adequate or not for your roof. For instance, pressure washing isn’t ideal for a roof in poor condition as it can aggravate current problems. It can also cause further damage.

Consult the manufacturer’s guidelines

Many roofing materials come with manufacturer guidelines and recommendations on cleaning and maintenance. There is valuable information on the most adequate cleaning methods, products, and techniques for the roof.

Manufacturer guidelines may advise against pressure washing. Take note of the recommendations to safely clean the roof without damaging it or voiding warranties.

Consider alternative cleaning methods

Not all roofing materials can withstand pressure washing. Delicate materials such as asphalt shingles or wood shales will require more gentle cleaning methods like soft washing, manual cleaning, and chemical treatments.

Ensure safe and successful roof cleaning

Here’s what you need to do to ensure safe pressure washing on your roof:

  • Reduce risks of falls and injuries

Cleaning the roof at heights is dangerous work. Turn to safety equipment, such as safety harnesses, ladders, and non-slip footwear to minimize the risk of falls and injuries. You want stability and protection from beginning to end.

  • Prevent accidents and damage

Roof cleaning involves using equipment such as pressure washers, which can cause accidents or damage if incorrectly handled. Expertise in operating equipment and following safety protocols reduces the risk of accidents and prevents damage to the roof, people on the ground, and surrounding property.

  • Protect personal health

When you clean the roof, you are exposed to hazards such as dust, debris, chemicals, and environmental pollutants. Wear adequate personal protective equipment (PPE), such as masks, goggles, gloves, and protective clothing. It’s how you can protect yourself against respiratory issues, eye injuries, skin irritation, and other health risks.

  • Employ correct technique

Expertise in roof cleaning techniques and methodologies ensures that the cleaning process is conducted effectively and efficiently.  The correct technique prevents damage to the roof surface, prevents water intrusion, and leads to excellent cleaning results.

  • Compliance with safety standards and regulations

Professionals adhere to safety standards and regulations, such as Occupational Safety and Health Administration (OSHA) guidelines. This ensures a safe working environment and reduces the risk of legal liabilities or penalties associated with workplace accidents or violations.

  • Reduce risks and prepare for emergencies

Being prepared for emergencies, such as accidents, injuries, or adverse weather conditions, is essential for reducing risks during roof cleaning. Knowledge of emergency procedures, first aid, and access to communication devices or emergency services ensure a prompt response to unexpected situations.

  • Professionalism and accountability

Turning to professionals or individuals with expertise in roof cleaning is a wise decision. It shows a commitment to safety, quality, and professionalism. Professionals understand the importance of safety equipment, expertise, and precautions and prioritize them to ensure safe and efficient roof cleaning.

Alternative roof cleaning methods

Soft washing

Soft washing is a gentle cleaning method that uses low-pressure water and specialized cleaning solutions to remove dirt, stains, algae, mould, and mildew. It’s appropriate for delicate roofing materials such as asphalt shingles, wood shales, and synthetic tiles.

Low-pressure sprayers and nozzle tips are used for safely clean the roof. To reduce environmental impact and protect plants, soft washing is used with biodegradable and eco-friendly cleaning solutions.


  • It’s gentle on delicate roofing materials and has a low risk of damage
  • It uses eco-friendly cleaning solutions and has a low environmental impact
  • It removes algae, mould, and mildew
  • It’s safe for landscaping and vegetation


  • It’s less efficient on difficult stains and heavy buildup
  • It requires specialized equipment and cleaning solutions
  • It takes time to give results
  • To ensure application and safety, it requires professional expertise

Manual cleaning

Manual cleaning refers to using non-abrasive tools and gentle scrubbing techniques to remove dirt, debris, stains, and algae. It’s a good cleaning option for delicate roofing materials such as cedar shingles, wood shakes, and clay tiles.

When pressure washing isn’t feasible or access to the roof is limited, manual cleaning is an adequate method. It requires attention to detail and various tools, like soft-bristled brushes, sponges, and scrubbing pads.

Manual cleaning can be used in conjunction with homemade solutions such as mild detergent and water.


  • It ensures precise control over the cleaning process
  • It has a low risk of damage
  • It’s adequate for delicate roofing materials and areas with limited access
  • It has a minor impact on the environment
  • It can be adjusted to target specific areas and stains


  • It takes a lot of time and effort
  • It requires physical effort
  • It’s not highly efficient on heavy buildup and extensive staining
  • It may require other forms of cleaning solutions

Chemical treatments

Chemical treatments refer to the application of specialized cleaning solutions or treatments to the roof surface to break down and remove dirt, stains, moss, algae, and mildew. It’s adequate for delicate roofing materials and roofs where physical cleaning isn’t efficient or practical.

The application of chemical treatments requires safety precautions, wearing protective gear (gloves, goggles, and respirators) and following manufacturer instructions for dilution, safety guidelines, and application.

After application, some chemical treatments require a period of dwell time to allow the solution to work. Rinsing with water may be necessary to wash away residues.


  • It can be tailored to the specific contaminants and stains
  • It’s efficient for targeting algae, moss, and mildew
  • It can be applied in difficult-to-reach areas and areas with limited access
  • It is less labour-consuming than manual cleaning


  • It requires careful handling and safety precautions
  • It may require several applications for difficult stains and heavily soiled areas
  • If incorrectly applied and disposed of, it can impact the environment
  • The efficiency depends on the type and severity of the stain

Recommendations for roof pressure washing

Here are some common recommendations for roof pressure washing from experts, roofing professionals, and manufacturers:

  • Examine the roof

Always conduct an in-detail inspection of the roof before pressure washing. You need to detect any damage, loose shingles, and areas of concern. Address any repairs and issues beforehand to prevent further damage during the cleaning.

  • Read manufacturer guidelines

Read the manufacturer guidelines and warranty specifications for the roofing material. Some manufacturers may include specific recommendations or restrictions regarding pressure washing. They may mention recommended pressure levels, cleaning solutions, and techniques.

  • Use low pressure

Use low-pressure washing techniques to reduce the risk of damage to the roofing material. High-pressure water can dislodge granules from asphalt shingles, damage flashing, or push water beneath roofing materials. It can lead to water intrusion and damage.

  • Select the proper nozzle

Use a wide-angle nozzle or a low-pressure tip to evenly spread the water and reduce the force of the water stream. Don’tuse narrow or high-pressure nozzles as they concentrate the water stream and damage the roof surface.

  • Pre-wet the roof

Before applying cleaning solutions or pressure washing, pre-wet the roof surface with water. It will loosen dirt, debris, and contaminants and prevent the cleaning solution from drying too quickly.

  • Turn to eco-friendly cleaning solutions

Opt for eco-friendly and biodegradable cleaning solutions that are safe for the environment and landscaping. Avoid harsh chemicals or bleach-based cleaners as they damage roofing materials and harm vegetation.

  • Work in sections

Divide the roof into manageable sections and work methodically to clean efficiently. Don’t spray water upward under the shingles, as you may push water beneath the roofing material and cause leaks.

  • Protect surroundings

Use plastic sheeting and tarps to cover plants, landscaping, gutters, and downspouts. You will protect them from cleaning solutions, runoff, or debris. To reduce environmental impact, you should rinse surrounding areas with water before and after pressure washing.

  • Take on safety precautions

Prioritize safety and wear adequate personal protective equipment (PPE), including gloves, goggles, and non-slip footwear. Use caution when working on ladders or at heights, and ensure proper ladder placement and stability.

  • Hire the professionals

For large and more complex roof cleaning jobs, you should hire professional roof cleaners. They are experienced and successfully clean large roofs and complex roofs. They carry the expertise, skills, and equipment to ensure stress-free pressure washing from beginning to end.

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