How to clean a Colorbond roof

Colorbond roofing is one of the most popular roofing materials in Australia thanks to its durability, weather resistance, and modern appearance. But like any exterior surface, it can collect dirt, mould, pollutants, bird droppings, and debris over time. Cleaning your Colorbond roof not only keeps it looking new but also helps preserve its protective coating and extend its lifespan.

This guide covers everything you need to know about cleaning a Colorbond roof safely and effectively, including the tools you'll need, the correct cleaning method, common mistakes to avoid, and when to call in a professional.

1. Why Cleaning a Colorbond Roof Matters

Colorbond steel is engineered to withstand harsh Australian conditions, but keeping it clean is still essential. Regular cleaning provides key benefits:

✓ Maintains Appearance

Dirt, pollution and leaf stains can make your roof look aged or discoloured. Cleaning restores its vibrant finish.

✓ Prevents Corrosion

While Colorbond is corrosion-resistant, build-up of debris or moisture can trap contaminants and reduce its effectiveness over time.

✓ Preserves Paint & Coating

Pollutants and mould can slowly degrade the baked-on paint finish. Cleaning prevents long-term wear.

✓ Improves Water Flow

Leaves, branches and grime can block roof channels, valleys and gutters, affecting water drainage.

✓ Reduces Heat Retention

A clean, reflective Colorbond surface helps maintain energy efficiency by reflecting heat more effectively.

2. What You’ll Need Before You Begin

Cleaning a Colorbond roof requires the right equipment to avoid scratching or damaging the metal coating. Gather:

• Sturdy ladder
• Non-slip shoes
• Safety harness (recommended for steep or high roofs)
• Garden hose with good pressure
• Soft-bristle brush or broom
• Bucket of warm soapy water (mild detergent)
• Softwash solution (optional)
• Gutter scoop
• Microfibre cloths
• Telescopic extension pole (for hard-to-reach areas)

Avoid:

• Abrasive sponges
• Harsh chemical cleaners
• Wire brushes
• High-pressure nozzles on full power

Using the wrong tools can damage the Colorbond finish, void warranties, or cause premature fading.

3. How to Clean a Colorbond Roof

Step 1: Inspect the Roof

Before cleaning, do a quick inspection from the ground and on the roof (if safe):

• Look for rust spots or scratches
• Check for loose screws or sheets
• Ensure flashings are secure
• Identify moss, mould or heavy dirt patches
• Remove branches or debris

If you see structural issues, it’s best to repair these before cleaning.

Step 2: Rinse the Roof with Clean Water

Use a garden hose to thoroughly wet the entire roof surface. This helps:

• Remove loose dirt
• Reduce the chance of scratching
• Soften debris
• Prepare for scrubbing

Always rinse from the top down to avoid pushing water underneath sheets.

Step 3: Apply Mild Soapy Water or Softwash Mix

Colorbond recommends only mild detergents or softwash cleaners to protect the paint coating. Mix:

• Warm water
• A small amount of mild dishwashing liquid or roof-safe detergent

Apply using a soft-bristle brush, sponge or sprayer. Avoid strong acidic or alkaline cleaners as they can damage the painted finish.

Step 4: Gently Scrub Problem Areas

Focus on stubborn sections such as:

• Bird droppings
• Moss or algae
• Tree sap
• Pollution stains

Use gentle pressure and work in long downward strokes. Avoid scrubbing across the sheeting ribs as this might leave visible abrasion marks.

Step 5: Rinse Thoroughly

Once cleaned, rinse the entire roof to remove detergent residue. Leftover soap can leave streaks or reduce the gloss of your Colorbond finish over time.

Step 6: Clean the Gutters

A roof clean often pushes dirt into your gutters. Make sure to:

• Scoop out leaves and debris
• Rinse the gutter channels
• Check downpipes for blockages

Clean gutters improve drainage and prevent overflow during heavy rain.

4. Cleaning Mould, Algae & Lichen on Colorbond Roofs

If your roof has mould or algae, you can treat it with a gentle softwash solution. The safest method is:

• Mix a diluted bleach solution (typically 1 part bleach to 4 parts water)
• Apply with a sprayer
• Let it sit for 10–15 minutes
• Gently scrub if required
• Rinse thoroughly

Avoid letting bleach dry on the roof, and do not use strong chlorine mixes because they can affect the coating.

Never use:

• High-strength acid
• Abrasive cleaners
• Caustic soda

These can permanently damage Colorbond steel.

5. Can You Pressure Wash a Colorbond Roof?

Yes — but with caution.

Pressure washing is safe only when done correctly, using:

• A wide fan nozzle
• Low to medium pressure
• Downward spraying direction
• Consistent distance from the surface

High pressure aimed directly at the sheet laps can force water into the roof cavity, leading to internal leaks and damage.

If you’re not experienced with pressure washing, it’s best to leave this step to a professional roof cleaner.

6. Cleaning the Exterior Walls After Roof Washing

Cleaning a Colorbond roof often causes dirty water, soap or mould residue to run down the walls. To keep your home looking fresh:

1. Rinse Walls Straight Away

Use a garden hose to wash down all exterior walls, preventing streaking and dried residue.

2. Use Mild Soapy Water for Streaks

If you notice dirt stuck to paint, brick or cladding:

• Apply warm soapy water
• Use a sponge or soft brush
• Rinse thoroughly

Avoid abrasive scrubbers that could damage painted surfaces.

3. Clean Windows & Screens

Roof runoff may splash onto:

• Window frames
• Screens
• Sliding door tracks

Wipe these areas with a cloth and warm water.

4. Light Pressure Wash (Optional)

For brick or concrete walls, light-pressure washing can remove stubborn stains. Keep it low pressure to avoid damaging paint or render.

7. How Often Should You Clean a Colorbond Roof?

Generally, Colorbond roofs should be washed every 12–24 months, but you may need more frequent cleaning if:

• You live near the ocean
• There are trees overhanging your home
• Birds frequently land on your roof
• You live in an industrial or high-pollution area
• Your roof receives very little sunlight

Regular maintenance helps prevent staining and prolongs the life of your roof’s coating.

8. Tips for Keeping Your Colorbond Roof Cleaner, Longer

• Trim overhanging branches
• Install gutter guards
• Remove debris after storms
• Schedule annual gutter cleaning
• Avoid harsh chemicals
• Inspect for scratches and touch up when needed
• Rinse the roof after fire season or heavy dust storms

9. When to Hire a Professional Roof Cleaner

Cleaning a Colorbond roof can be dangerous due to slippery surfaces and the risk of falls. You should hire a professional if:

• Your roof is steep or two storeys
• You’re not confident working at heights
• There’s heavy mould or algae build-up
• You need pressure washing
• The roof hasn’t been cleaned in many years
• You want to avoid damaging the Colorbond coating

Professionals use the correct low-pressure equipment and roof-safe cleaning agents to deliver a long-lasting, streak-free result.

Conclusion

A Colorbond roof is designed to last, but regular cleaning is essential to maintain its appearance and performance. With the right cleaning techniques—using mild detergents, gentle scrubbing, proper rinsing and safe pressure washing—you can keep your roof looking its best for years.

If you need help cleaning your roof, get in touch with Rapid Roof Services in Sydney - your professional roof cleaners.