How to Wash Asphalt Shingle Roofs: Soft Wash Guide

Washing asphalt shingles requires a very different approach than pressure washing siding or concrete. In this guide, we’ll walk you through the soft wash method, which removes black streaks, algae, moss, and lichen without damaging shingles. The process uses a stronger chemical mix than house washing and must be handled with care to avoid plant damage, chemical overspray, or personal injury.

What Is Soft Washing for Roofs?

Soft washing is the industry-standard method for cleaning asphalt shingles. It uses a low-pressure application of a high-strength sodium hypochlorite mix (bleach + surfactant) to kill and dissolve organic growth like algae, moss, and lichen. Unlike pressure washing, which can damage shingles, soft washing lets chemistry do the work.

Key Note: We do not rinse the mix off the roof. The longer it dwells, the more effective it is. Rain events help rinse away the remaining residue. We often tell our customers: "It took 20 years for the buildup on your roof to form; it might take a few weeks for it to be fully washed off."

Before and After

Soft Wash Roof Cleaning Process

1. Protect the Property: Constantly spray surrounding vegetation and lawn with water before, during, and after applying the roof mix. (Pro tip: It is very beneficial to have a second person solely spraying water around the work area).
2. Bag All Downspouts: Secure plastic bags or neutralizer buckets to the ends of all downspouts to capture and neutralize runoff. This prevents bleach runoff from killing grass and plants.
3. Mix Solution: Use a higher concentration than house wash—often a 3–6% sodium hypochlorite mix with a surfactant (like Eliminator or Dragon Juice). This “hot mix” is necessary to kill moss, algae, and lichen.
4. Apply Chemical: Use a soft wash system or dedicated 12V pump setup to apply the solution evenly to the shingles. Start at the gutter line and work towards the ridge (same method as house washing).
5. Limit Overspray: Overspray is when solution lands on things other than the shingles—like windows, cars, or plants. Always adjust the tip and be cognizant of where you are spraying.
6. Observe Results: Organic growth will begin turning brown or white within minutes. If the moss stays green, apply another coat.
7. Do NOT Rinse: Leave the mix on the roof. This allows time for it to kill all growth and lets rain wash it away safely.

Action in Progress

Safety Considerations

• Wear a respirator: The bleach mist from soft washing can cause lung irritation or long-term damage. Always wear proper PPE.
• Use ladder safety: A telescoping ladder is preferred for roof access because it’s lightweight and fits in tighter areas. Here’s a good one: Telescoping Ladder.
• Consider Cougar Paws: These roofing boots grip shingles safely. They’re a must if you need to walk any part of the roof. Cougar Paws Boots.
• Do not spray near electrical service lines: Be aware of power lines, cable runs, and satellite dishes while working around roofs.

Pro Tips

• Only soft wash in calm conditions—wind will blow mist and increase overspray risks.
• Use a dedicated roof pump—not a downstream injector. The mix needs to be much stronger than what downstreaming can deliver.
• Walk customers through what to expect—full results may take 1–3 weeks after treatment.
• Keep extra surfactant in your mix to help it cling to steep roof pitches and shed less quickly.

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