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A Comprehensive Guide to Roof Washing

Residential Roof Cleaning & Moss Removal in Vancouver, BC

When it comes to roof washing in Canada, the first step is to identify your roof type. Equally important is having the knowledge and expertise to effectively and safely clean your specific roof type. Furthermore, understanding your roof's current condition is essential to avoid wasting time and resources on cleaning a roof that might actually require replacement.

In this blog post, we'll explore four common roof types found in Canada and discuss:

  1. Identifying Roof Types and Their Characteristics

  2. Assessing Roof Conditions

  3. Safely Cleaning Your Roof

  4. Maintaining Your Roof for Longevity

Accurately determining your roof's material is crucial because it enables you to:

  • Gauge its expected condition considering its age.

  • Choose the appropriate cleaning and maintenance methods.

In Canada, the most frequently encountered residential roof types include:

1) Asphalt Shingle Roofs

Ashphalt Shingle Roof Cleaning in Vancouver, BC
Ashphalt Shingle Roof Cleaning in Vancouver, BC


  • Asphalt roofs are recognizable by their flat, sleek appearance and sand granules on the shingle surface.

  • They are cost-effective, excellent at reflecting sunlight, and fire-resistant—making them popular in wildfire-prone areas or communities with closely spaced houses.

  • A new asphalt roof appears clean, with intact sand granules and shingles free from cracks or curling. Over time, exposure to the elements will manifest as wear and tear.

Cleaning Process:

  • To clean an asphalt roof, begin by brushing off heavy moss at the shingle overlaps. Attach a moss brush to a pole for efficient moss removal.

  • Next, either leaf blow (in dry conditions) or gently rinse (if it's raining) the moss into the gutter system. Ensure the gutters are thoroughly cleaned.

  • The next step involves applying a 4-6% mixture of sodium hypochlorite and roof-washing soap evenly across the entire roof. Leave the mixture to naturally clean the roof with the help of rain, wind, sun, and snow.

This method not only enhances the roof's appearance but also extends its lifespan without compromising its integrity. While brushing can be slightly detrimental to the shingles, regular maintenance eliminates the need for repeated brushing.

Maintenance: Maintain the roof's cleanliness by re-spraying it every 2-4 years, ensuring clean gutters before each application.

2) Cedar Roofs

Cedar Shake Shingle Roof Cleaning in Vancouver, BC
Cedar Shake Roof Cleaning in Vancouver, BC


  • Cedar roofs are easily recognizable by their large wooden shingles, which can vary in size.

  • A new cedar roof boasts rich colour and shingles free from lifting or curling.

Cleaning Process:

  • To clean a cedar roof, start by removing loose debris through leaf blowing or gentle rinsing.

  • Clean out the gutters to facilitate drainage during the cleaning process.

  • Apply CWB Solutions 'Gold Assassin detergent to the surface of the roof using a downstream injector. Let the solution dwell for 15-20 minutes.

  • Using a pressure washer rated for 4-8 gallons per minute, gently rinse the shingles with a nozzle rated for twice your machine's capacity. This reduces pressure and minimizes the risk of damage. Use a maximum PSI of 2500.

  • After rinsing with a pressure washing, apply a diluted oxalic acid treatment to the roof with a downstream injector. Let it dwell for 10-15 minutes. This treatment brightens the cedar shakes to restore their natural colour.

  • Repeat the fourth step, and thoroughly rinse the roof using a high-volume pressure washing.

  • Lastly, apply roof coating to hydrate and protect it from the elements.

Maintenance: Cedar roofs require infrequent cleaning. When needed, repeat the same process and periodically remove loose debris, preferably during warm, sunny weather when the roof and debris are dry.

3) Metal Roofs

Metal Roof Cleaning in Vancouver, BC
Metal Roof Cleaning in Vancouver, BC


  • Metal roofs consist of large sheets of thin metal, often corrugated, and are commonly used in snowy regions due to their snow-shedding properties.

  • They do not naturally accumulate moss but can collect debris from overhanging trees.

  • A well-maintained metal roof will be free of bends and loose screws, with a uniform paint coating.

Cleaning Process:

  • For cleaning, spray the roof with a 2-3% sodium hypochlorite and roof-washing soap mixture and rinse it off for an immediate clean look.

  • Pressure washing without detergent is an option, but it can be time-consuming and potentially damaging.

Maintenance: Re-spray the roof every 2-4 years, with the frequency depending on the roof's pitch. Steeper roofs require less frequent cleaning.

4) Concrete/Tile Roofs

Concrete/Tile Roof Cleaning in Vancouver, BC
Concrete/Tile Roof Cleaning in Vancouver, BC


  • Concrete/tile roofs are heavy and often painted for added protection.

  • They are easily recognizable due to their uniform appearance, with identical-sized and shaped tiles.

  • Concrete roofs are energy-efficient, helping to regulate indoor temperatures.

Cleaning Process:

  • **Before cleaning, ensure there are no cracked or broken tiles. Replace any damaged tiles before proceeding.

  • To clean a concrete roof, begin by leaf blowing or rinsing the entire roof.

  • Clean out the gutters and then apply a 4-6% mixture of sodium hypochlorite and roof-washing soap.

  • After allowing the mixture to sit for 10-15 minutes, use a pressure washer (up to 2500 PSI, following the same nozzle recommendations as mentioned for cedar roofs) to remove algae and moss.

  • Afterward, clean the gutters again and install Gutter Baskets. Respray the entire roof with the mixture to inhibit organic growth and extend cleanliness.

Maintenance: Maintaining a concrete roof is similar to cedar roofs—periodically remove loose debris and respray every 4-5 years.

Special Considerations

Note that the climate in your area will impact your roof's condition over time, including UV damage, oxidation, cracking, or organic growth. Adapt your maintenance accordingly based on your specific climate and roof type.

Maintaining the roof of your Canadian home is vital to its longevity and aesthetic appeal. Roof washing, when done correctly, can enhance the curb appeal of your property and extend the life of your roof. However, it's crucial to understand the specific needs of your roof type and follow a safe and effective cleaning process. In this guide, we'll explore the four most common roof types in Canada and provide insights into determining their type, assessing their condition, safely cleaning them, and maintaining their integrity.

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