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April 27, 2024

Pros and Cons of Different Roof Cleaning Methods

The average roof can accumulate up to 2 kilos of dirt per square foot. As homeowners, we often overlook the importance of roof maintenance. From pressure washing to manual cleaning and chemical treatments, their pros and cons, we discuss in detail right down below.

Pros and Cons of Different Roof Cleaning Methods

Roof cleaning method no.1: pressure washing

Pressure washing a roof involves using high-pressure water jets to remove dirt, debris, stains, and organic growths from the roof’s surface. The pressure washer has a nozzle that emits a concentrated stream of water at high velocity. It will efficiently dislodge and wash away contaminants from the roof’s surface.

How it’s done

During the pressure washing process, water is pumped through a hose attached to the pressure washer. An operator will direct the high-pressure stream onto the roof’s surface. The force of the water jet breaks down and removes dirt, moss, algae, lichen, and organic matter.

Pressure washing is highly effective at cleaning vast roof areas and it’s popular for removing difficult stains and heavy soilage. To avoid damage to the roofing materials, it’s crucial to use the correct pressure settings and techniques. Improper settings cause erosion, cracking, and dislodging of tiles and shingles.

Professional roof cleaners know how to safely and efficiently use the pressure washer. They adjust the pressure settings and use the adequate techniques to clean without damaging the roof. Professionals may turn to eco-friendly cleaning solutions to improve the efficiency of cleaning without harming the environment.

The pros of pressure washing the roofs

  • Efficient cleaning

Pressure washing is highly efficient at removing difficult stains, dirt, debris, and organic growths from the roof. The high-pressure water jet goes deep and dislodges difficult contaminants. The roof will be clean and look better than ever before.

  • It’s fast

With pressure cleaning, large roof areas can be quickly cleaned. The powerful water stream covers wide surface areas in a short amount of time. Pressure washing is a time-saving method.

  • It’s versatile

Pressure washing is adequate for various kinds of roofing materials, such as: asphalt shingles, tiles, metal roofing, etc. Professionals adjust pressure washing to various roof slopes, textures, and configurations. It’s a versatile cleaning method with excellent results for many roof structures.

Regular pressure washing prevents buildup of dirt, debris, and organic growths on the roof. It prevents roof degradation, expands its durability, and reduces the need for repairs and replacements.

  • It restores the roof’s appearance

Pressure washing may significantly change for the better the roof’s appearance. It removes unsightly streaks, stains, and discoloration from algae, dirt, moss, and lichen. A clean roof improves the curb appeal of the property and its perceived value.

  • It works with eco-friendly solutions

Pressure washing can be used with eco-friendly cleaning solutions to improve the cleaning results and reduce environmental impact. The eco-friendly cleaners break down organic matter and don’t harm the ecosystem.

The cons of pressure washing

Even if not major, the cons of pressure washing need mentioning to present an accurate picture of pressure washing for roofs. Here are the most important downsides of roof pressure washing:

  • Risk of damage

When incorrectly performed, pressure washing can damage the roofing materials. Excessive water pressure or incorrect techniques may cause cracking, erosion, and dislodging of tiles, shingles, and roofing components. Water infiltration and structural damage may occur.

  • Water intrusion

Pressure washing can make water reach under shingles or tiles, especially when roofing materials are old and damaged. Water will penetrate the roof structure and building’s interior and cause leaks, moisture damage and mould growth.

  • Risk for personal safety

Pressure washing is performed at heights so there is a risk to personal safety for property owners and contractors. Falls, slips, and injuries from equipment may happen. Professionals follow strict safety protocols such as fall protection gear and securing ladders. During pressure washing, the surfaces become wet or slippery and increase the risk of accidents.

  • Possible environmental impact

Wastewater from pressure washing contains dirt, debris, and contaminants that may harm the environment. Runoff from pressure washing may pollute soil, waterways, and aquatic habitats. It can also affect plants, animals, and ecosystems.

Professionals employ correct containment, filtration and disposal of wastewater to reduce environmental impact of pressure washing.

  • Limited efficiency on some contaminants

Even if pressure washing is efficient at removing dirt, debris, and organic growths from the roof’s surface, it’s not efficient at removing some contaminants. For example, pressure washing cannot remove algae spores from roofing materials. Additional treatments and followup cleaning are necessary as well.

  • Cost considerations

Professional pressure washing services can be expensive, especially for complex roof structures and large roof areas. The costs may increase if pressure washing causes roof damage and leads to repairs or replacements.

Roof cleaning method no.2: soft washing

Soft washing is gentler than pressure washing as it uses low-pressure water along with specialized cleaning solutions to remove dirt, stains, algae, moss, and other contaminants. Soft washing is based on the chemical action of cleaning solutions and a gentle rinsing afterwards.

How is soft washing done

During the soft washing procedure, the technicians use a low-pressure sprayer or pump system to apply on the roof a mixture of water and biodegradable cleaning agents (detergents, surfactants, and mildewcides). The cleaning solution will dwell on the roof for some time (10-15 minutes).

After the cleaning solutions has penetrated and loosened dirt, algae, moss, and organic growths, the cleaners rinse the roof with low-pressure water. They will wash away the loosened contaminants, residues, and cleaning solution. The rinse doesn’t damage the roofing materials and removes debris.

Soft washing is suitable for delicate roofing materials such as: clay tiles, asphalt shingles, and wood shakes. It’s a safe and efficient solution for roofs with fragile or aging surfaces. It has a low risk of cracking, erosion, and dislodging of roofing components.

The pros of soft washing

The list of pros for roof soft washing includes and doesn’t resume to:

  • It’s a gentle method

Soft washing uses low-pressure water and specialized cleaning solutions to gently remove stains, dirt, algae, moss, and contaminants from the roof surface. The gentle cleaning protects delicate roofing materials and reduces the risk of cracking, erosion, and dislodging roof components.

  • It’s safe for delicate roofing materials

Aging or fragile surfaces such as wood shakes, asphalt shingles or clay tiles can benefit from soft washing. The low-pressure water delivery and eco-friendly cleaning solutions reduce the risk of damaging the roofing materials.

  • It efficiently removes organic growth

Soft washing efficiently addresses and removes organic growths such as algae, moss, and lichen. The specially formulated cleaning solutions go deep, dissolve the root systems of the growths and ensure effective removal. The method also prevents regrowth.

  • It prevents streaking and discoloration

Soft washing prevents streaking, discoloration, and alteration of the finishes and landscaping. The cleaning results are uniform thanks to controlled application of the cleaning solutions and the gentle rinsing.

  • It’s environmentally friendly

Biodegradable cleaning agents and eco-friendly solutions are used with soft washing. They have low environmental impact and don’t harm the nearby vegetation, water bodies, and eco-systems. Soft washing is safe and sustainable and aligns with environmentally conscious procedures.

  • Its results are long-lasting

Soft washing offers long-lasting cleaning results as it removes contaminants and organic growths from the roof’s surface. With adequate maintenance and regular treatments, soft washing prevents recurrence of algae, moss, stains, and lichens.

  • It’s safe for nearby landscape

Plants, vegetation and landscaping near the roof won’t suffer from soft washing. The risk for the biodegradable cleaning solutions and the low-pressure water delivery to damage plants is minor. The landscaping will stay unharmed throughout the entire soft washing procedure.

The cons of soft washing

  • It’s a slow method

Soft washing takes more time and effort than pressure washing, especially in case of heavily soiled and difficult stains. The dwell time for cleaning solutions and the gentle rinsing process take a lot of time. The labor costs and inconvenience for property owners increase significantly.

  • The efficiency on tough stains is limited

Even if soft washing efficiently removes dirt, algae, moss, and lichen from the roof surface, it has limited efficiency on heavily soiled or deeply embedded stains. For difficult stains, additional treatments and follow-up cleaning may be necessary.

  • It can leave an odour

Some cleaning solutions may leave residual odours or chemical smells after the cleaning. Most cleaning agents are odour less or have minor scent. However, some people will notice a bothersome residual odour from soft washing.

  • There is a risk of incomplete cleaning

Soft washing is based on the chemical action of cleaning solutions. Improper application or rinsing of cleaning solutions can lead to incomplete cleaning or residues. This can alter the appearance of the roof and affect the efficiency of the cleaning process.

  • There are environmental concerns due to chemicals

Biodegradable cleaning agents and eco-friendly solutions are used with soft washing. However, there are concerns with regard of environmental impact of chemicals. Incorrect disposal or runoff of cleaning solutions may contaminate soil, waterways, and aquatic habitats, harm plants, animals, and ecosystems.

  • It’s not always cheap

Professional soft washing can be expensive for large roof areas or complex roof structures. The specialized cleaning solutions, equipment, and the additional labour increase the costs, especially when compared to other cleaning methods.

Cleaning method no.3: manual cleaning

Manual cleaning refers to using hand tools, brushes, and scrubbing implements to physically remove dirt, debris, and stains. Unlike soft and pressure washing that rely on water delivery, manual cleaning entails direct physical contact and mechanical agitation to dislodge and remove contaminants from roof.

How is manual cleaning done

Manual cleaning is done in several ways:

Hand scrubbing

Hand scrubbing means manually scrubbing the roof with brushes, scrubbing pads, and abrasive sponges to remove dirt, stains, moss, algae, and various contaminants. It employs physical effort and attention to detail for thorough cleaning.


Stiff-bristled brushes and brooms are used for brushing away debris, leaves, and loose contaminants from the roof’s surface. Brushes with long handles or extension poles can be used to reach areas with difficult access or steep roof slopes. Brushing removes surface debris and prevents buildup of organic matter.


The cleaners use putty knives, scrapers, or wire brushes to scrape away difficult stains, moss, algae, or lichen. Scraping gives results with thick or crusty deposits that brushing and scrubbing alone cannot remove.

Manual picking

Manual picking means manually remove debris, twigs, leaves, and foreign objects from the roof’s surface. It takes a lot of time and energy, but it allows precise removal of individual items. It also helps with inspection of the roof and detection of signs of damage.


Manual cleaning methods are typically used together with other roof maintenance practices, such as gutter cleaning, roof inspection, and minor repairs. They are suitable for delicate roofing materials that don’t withstand pressure washing or harsh cleaning chemicals. It can be adjusted to the particular needs of the roof and surrounding environment.

The pros of manual cleaning

  • It’s a gentle cleaning action

Manual cleaning methods represent gentle cleaning action that reduces the risk of damage to roofing materials. The roof’s structure remains intact after cleaning.

  • It ensures precise control

Manual cleaning allows precise control and the operator can focus on specific areas or stains for thorough removal of contaminants.

  • It’s safe for delicate materials

Manual cleaning methods are safe for delicate and sensitive roofing materials that pressure water jets and harsh chemicals would damage.

  • It’s environmentally friendly

Manual cleaning methods don’t require the use of water or cleaning solutions. They are environmentally friendly and sustainable.

The cons of manual cleaning

  • It’s labour intensive

Manual cleaning methods are labour intensive and require a lot of physical effort. Additionally, scrubbing, brushing, or scraping the roof’s surface takes time, especially for large roof areas or roofs with complex structures.

  • It takes time

Manual cleaning methods can take longer to complete than pressure and soft washing. Scrubbing, brushing, and scraping every area of the roof surface can take a lot of time.

  • It has limited coverage

Manual cleaning methods have rather limited coverage compared to pressure and soft washing. Manually clean a roof is complicated for difficult-to-access areas and steep roof slopes. Some areas may be skipped or incomplete.

  • There’s a risk to damage the roofing materials

Even if it’s rather gentle, manual cleaning techniques still pose a risk of damage to delicate roofing materials. Aggressive scrubbing and abrasive tools may cause scratching, abrasion, and dislodging of shingles, tiles, and other roof components.

  • It’s not efficient for difficult stains and contaminants

Manual cleaning methods aren’t highly efficient for removing difficult stains, moss, algae or lichen from the roof’s surface. Some contaminants will require supplemental treatments or more intensive cleaning methods to obtain good results.

  • It has limited accessibility

Manual cleaning methods are challenging on roofs with inaccessible structures, such as several levels, steep pitches, and obstacles (skylights, chimneys). Such areas will require specialized equipment and elaborate safety measures. The complexity and costs will significantly increase.

  • It poses risk for injuries or accidents

Manual cleaning methods involve working at heights, which always is risky. Falls, slips, and injuries from handling the tools may take place. Professionals will use fall protection gear or securing ladders. The surfaces may get slippery or wet and increase the risk of accidents.

Cleaning method no.4: chemical treatments

Chemical treatments for roof refer to application of specially formulated solutions and treatments on the roof. They eliminate algae, moss, lichen, and other organic growths. The treatments are typically biocides, algae inhibitors, and antimicrobial agents that aim and stop the growth of microorganisms on the roof.

The chemical treatments for roof

Several chemical treatments are used for roof maintenance:


Biocides are chemical substances that are formulated to kill or inhibit the growth of living organisms, algae, moss, lichen, fungi, and bacteria. Biocides disrupt cellular processes and metabolic functions within the microorganisms. Therefore, the microorganisms will die or stop growing.

Professionals apply biocides on the roof’s surface as a spray or solution and allow it to dry. The active ingredients will penetrate and work against the contaminants in time.

Algae inhibitors

Algae inhibitors are chemical compounds made to prevent the growth of algae on the roof’s surface by creating a hostile environment that blocks algae colonization and proliferation. Copper and zinc compounds, and various proprietary formulas will produce trace amounts of metal ions in time.

The metal ions are toxic to algae and block their growth. Algae inhibitors take forms of coatings, shingles, or granules embedded in roofing materials. They offer protection against algae infestation for a long time.

Antimicrobial agents

Antimicrobial agents are chemical substances that aim and block the growth of many microorganisms, such as fungi, algae, and mould. Quaternary ammonium compounds, silver nanoparticles, or other antimicrobial formulations are agents that disrupt microbial cell membranes, enzymes, or dna replication processes.

Quite often, the antimicrobial treatments are included into roofing materials. They can also be applied as surface coatings to offer ongoing protection against microbial growth.

The pros of chemical treatments

  • They offer long-term protection

Chemical treatments offer long-term protection against algae, moss, lichen, and other organic growths. They block their growth and prevent colonization on the roof surface. Regular application of chemical treatments keeps the roof nice and clean and lowers the frequency of cleaning.

  • They work as preventive measures

Chemical treatments work as preventive measures that protect the roof’s surface from microbial infestation. They create a hostile environment for algae, moss, and various contaminants.

  • Some are environmentally friendly

Some chemical treatments are environmentally friendly and have low impact on the environment. They don’t harm the nearby vegetation, water bodies, and ecosystems. Algae inhibitors and biodegradable biocides protect against microbial growth and align with environmentally conscious practices at the same time.

  • They are compatible with roofing materials

Chemical treatments are compatible cu many types of roofing materials, such as: tiles, asphalt shingles, metal roofing, and more. They work on new and current roofs to offer long-lasting protection against microbial infestation and maintain the cleanliness and appearance of the roof.

The cons of chemical treatments

  • They pose a possible environmental impact

Some chemical treatments pose environmental risk when not used or disposed of correctly. Biocides, algae inhibitors, and antimicrobial agents may include toxic substances. The toxic substances seep into the soil, waterways, and surrounding ecosystems and pose risks to animals, plants, and aquatic habitats.

Incorrect application or runoff of chemical treatments can pollute and degrade the environment.

  • They raise health concerns

Chemical treatments pose health risks to people exposed to the treated roof or fumes from the application. Skin contact or inhalation of chemical solutions and residues may cause allergic reactions, irritation, and respiratory problems in some people.

The professionals wear protective gear and follow strict safety protocols to reduce health risks when applying chemical treatments.

  • Their efficiency is limited on existing growth

Chemical treatments have limited efficiency on existing algae, moss, lichen, and organic growth, especially when compared to pressure washing or manual scrubbing. Chemical treatments don’t completely eradicate current contaminants. Additional cleaning will be needed.

  • They are not cheap

The costs for chemical treatments can be high, especially for large roofs or roofs with complex structures.

  • The efficiency has limited duration

Chemical treatments don’t offer permanent protection against algae, moss, lichen, and various contaminants. To maintain efficiency, chemical treatments require regular re-application. Weather conditions, exposure to sunlight, and roof material composition influence the durability.

When the consistent treatment cannot be maintained, the efficiency decreases and the risk of microbial infestation increases.

  • They may damage the surrounding surfaces

When not carefully applied, chemical treatments may damage surrounding surfaces or landscaping. Overspray or runoff from the application process may stain or discolor exterior finishes, siding, windows, or vegetation.

Chemical treatments may damage the appearance and integrity of the property. Professionals will contain the chemical treatments to minimize accidental damage to surrounding surfaces.

Let’s sum up the pros and cons of every roof cleaning method

Pressure washing


  • Efficient cleaning of difficult stains, dirt, and organic growth
  • It’s efficient for large roof areas
  • It’s versatile
  • It gives the roof back its initial appearances


  • If not correctly done, it can damage the roofing materials
  • If not properly executed, it can cause water intrusion
  • It requires specialized equipment and expertise
  • It presents environmental concerns with runoff and dispose of wastewater

Soft washing


  • It’s adequate for delicate roofing materials
  • It removes organic growths without causing damage
  • It prevents streaking and discoloration
  • It’s environmentally friendly


  • It takes more time than pressure washing
  • It’s not highly effective on difficult stains and deeply embedded contaminants
  • It can cause residual odour
  • It’s more expensive than manual cleaning

Manual cleaning


  • It’s gentle and precise
  • It’s safe for delicate roofing materials
  • It’s environmentally friendly
  • It’s cost-efficient for small roof areas


  • It takes a lot of time and effort
  • It has limited coverage
  • It can damage the roofing materials
  • It’s not efficient on stubborn stains and deeply embedded contaminants

Chemical treatments


  • They ensure long-term protection against organic growths
  • They inhibit microbial infestation
  • Some are environmentally friendly
  • They work for many roofing materials


  • They pose environmental impact when improperly used or disposed of
  • They pose health concerns
  • The efficiency is limited on existing growth
  • They are expensive and require periodic reappllication

When to use each of the roof cleaning method

Pressure washing

  • Heavy contamination, heavy stains, dirt buildup, and extensive organic growths (algae, moss, and lichen).
  • Large roof areas like commercial buildings and large houses
  • Sturdy roof materials like concrete tiles, metal, or asphalt shingles
  • When one wants immediate results

Soft washing

  • Delicate roof materials such as cedar shingles, wood shakes, or slate
  • As a preventive maintenance measure to block algae, moss, and lichen growths on roofs prone to microbial infestation and in areas with shade and high humidity.
  • For roofs with delicate finishes or architectural details
  • When eco-friendly cleaning solutions and minimal environmental impact are top priorities

Manual cleaning

  • For localized contamination, spot treatments, and small areas of contamination
  • For historic or architectural roofs with intricate details, ornamental features or delicate materials
  • For diy enthusiasts or homeowners who prefer hands-on cleaning methods
  • When the budget is tight

Chemical treatments

  • When there’s a need for preventive measures against microbial infestation
  • For long-term protection against organic growths, especially in regions with humid climates or frequent rainfall
  • When environmentally friendly solutions are preferred
  • For low-maintenance solutions
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