Welcome back to the channel! Today, I’m taking you through a quick yet informative project: cleaning a fiberglass roof over a carport. While this might sound like a routine job, there’s a lot to learn—especially if you’re new to roof cleaning and considering starting a pressure washing business. One of the most common questions I get is: “Can you clean a roof using just a pressure washer?” Let’s dive in.
Revisiting a Fiberglass Roof
In 2020, I cleaned this exact fiberglass roof, and it was so heavily covered in organic growth (like algae and leaves) that you couldn’t even see through it. Fast-forward to now, and you’ll find only minor specks of organic matter. This transformation proves how effective the right mix of cleaning solution can be, especially when applied properly and left to work its magic.
Fiberglass vs. Asphalt: Key Differences
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Fiberglass Roofs:
- Can handle a bit more agitation.
- You can apply a low to moderate pressure rinse to help remove stubborn debris.
- Risk of damage is minimal compared to asphalt, but you still need to be cautious and use the correct techniques.
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Asphalt Shingles:
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Never use high pressure to clean; it can strip off granules and compromise the roof.
- Best cleaned with a soft wash approach—low pressure and the right chemical mix.
- Rinsing asphalt shingles is optional; letting the solution and natural rainfall remove stains over time can be highly effective.
How We Cleaned This Fiberglass Roof
My colleague Ben tackled the job with a 10 GPM pressure washer—but don’t let that fool you. The pressure washer is more for rinsing than blasting away grime. Thanks to a “skunk valve,” we were able to use a somewhat stronger mix than typical downstream injectors can provide. However, for heavily stained surfaces or delicate roofing materials, a dedicated soft wash system remains the gold standard.
Why Use a Soft Wash System?
- It allows you to apply a hotter mix (stronger chemical concentration) at very low pressure.
- Ideal for removing organic growth—moss, algae, lichen—without risking structural damage.
- Essential for materials like asphalt shingles that don’t tolerate high pressure.
The Simple Answer to a Big Question
So, can you clean a roof with a pressure washer? The short version is no, at least not in the way most people think.
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Fiberglass Roofs & Metal Roofs: Rinsing at low pressure can help, and a little agitation is okay if you’re careful.
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Asphalt Shingles: Skip direct pressure altogether. A low-pressure soft wash is safer and more effective.
My Personal Preference: The Soft Wash Approach
I often prefer not to rinse at all when dealing with asphalt shingles. Instead:
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Spray the Shingles: Use the appropriate soft wash solution.
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Let It Sit: Allow the chemicals to do the heavy lifting, breaking down organic matter at the root.
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Protect Landscaping: Always pre-rinse and post-rinse nearby plants and grass.
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Wait on Mother Nature: Rainfall in the following 30–60 days typically washes away any remaining residue, leaving the roof looking new.
Want to Master Roof Cleaning?
If you’re thinking about starting or growing a pressure washing business, knowing how to clean roofs properly is a game-changer. It’s not just about removing dirt—it’s about protecting surfaces and ensuring lasting results for your customers.
That’s why I recommend checking out the How to Wash course, which walks you step-by-step through:
- Choosing and maintaining the right equipment.
- Mixing chemicals safely for each surface type.
- Properly cleaning every area of a residential property.
- Essential property protection methods to keep landscaping pristine.
This course could save you countless hours of trial and error and help you avoid costly mistakes. It’ll be the first link in the comment section and in the description if you’re watching this on YouTube.
Final Thoughts
Roof cleaning is an art as much as it is a science. Understanding the materials you’re dealing with and choosing the right cleaning method sets you up for success. While a pressure washer can help with certain roof types, like fiberglass or metal, it’s rarely the best tool for asphalt shingles. A soft wash system is by far the safer and more effective approach for those more delicate materials.
If you found this post helpful, subscribe to stay updated on the latest pressure washing tips. Don’t forget to hit the like button if you enjoyed the content. See you in the next post—and remember, cleaning smarter (not harder) always wins in the long run!
Ready to Perfect Your Roof Cleaning Skills?
Stay safe, stay efficient, and happy cleaning!
