Asphalt shingle roofs often accumulate unwanted growths such as moss, lichen, algae, and grime over time. These growths can harm the appearance of your home — and worse, compromise the integrity of your shingles. That’s why proper cleaning and maintenance are essential.
Why Regular Cleaning Matters
- Over time, moisture, shade, and organic debris encourage the growth of moss, lichen, algae, and mildew on asphalt shingles. These organisms cling to the roof surface, hold water, and can slowly deteriorate shingles.
- Moss and lichen in particular are problematic — moss retains moisture like a sponge, while lichen (a mix of algae and fungus) can form tough, crusty patches that are difficult to remove.
- Left unchecked, these growths can loosen or lift shingle granules, exposing the asphalt and fiberglass layers underneath to the elements, which accelerates wear and shortens roof lifespan.
Why Soft Washing Is Recommended — Not Pressure Washing
When cleaning asphalt shingle roofs, the method you choose is just as important as cleaning itself. High-pressure washing (e.g. with power washers) is strongly discouraged. The force of pressurized water can strip away the protective granule layer on shingles — leaving them vulnerable to UV radiation, weathering, and premature deterioration.
Instead, the safest and most effective method is soft washing. In soft washing:
- A gentle, low-pressure spray applies a specialized cleaning solution. This solution penetrates and kills organic growth like moss, lichen, algae, and mildew, rather than blasting them off with brute force.
- Once the cleaning solution has done its work, the roof is rinsed gently (often with just a garden hose), preserving the protective granules while removing dead organic matter and loosened debris.
- Soft washing doesn’t just restore the roof’s look; by killing the root of moss and lichen growth and avoiding abrasive damage, it helps extend the life of your roof.
The Process of Roof Moss Removal & Roof Cleaning
Here’s a simplified outline of how to clean and remove moss, lichen, and other organic growth from an asphalt roof safely and thoroughly:
- Inspect & Identify — Look for dark streaks, patches of green or gray, fuzzy moss, or crusty lichen. These may indicate growths that need cleaning.
- Prepare the Area & Protect Surroundings — Before applying any solution, protect vegetation, plants, windows, and metal surfaces from chemical over spray. Rinse nearby plants or cover them if needed.
- Use Appropriate Cleaning Solution — Use a roof-safe cleaner formulated for asphalt shingles. Many effective soft-wash solutions are oxygen-based or mild bleach-based without being overly aggressive.
- Apply With Low Pressure (Soft Wash) — Use a pump sprayer or low-pressure hose to coat the roof evenly. Avoid high-pressure washers or stiff brushes that can damage shingles.
- Let the Solution Work (Dwell Time) — Allow the cleaning solution to sit on the roof for the recommended time so it can kill moss, lichen, algae, and mildew effectively.
- Rinse Gently From Top Down — Once dwell time is over, rinse the roof gently with a low-pressure spray or garden hose, working from the top downward to flush off loosened debris and dead organisms.
- Inspect & Repeat If Necessary — For stubborn patches of moss or lichen, you may need to reapply the solution or do targeted spot treatment. Regular cleaning helps prevent regrowth.
Long-Term Maintenance & Prevention
- Inspect Regularly. Check your roof at least once a year (often after rainy seasons) to catch moss, lichen, or algae early before they spread.
- Address Moisture & Shade. Moss and lichen thrive in damp, shaded areas. Improving ventilation, trimming overhanging branches, or ensuring better sunlight exposure can help prevent regrowth.
- Use Soft-Wash Maintenance Instead of High-Pressure Cleaning. Schedule periodic soft washing (every few years or as needed) to keep growths under control without damaging shingles.
- Protect Surrounding Landscaping. Whenever you perform roof cleaning, make sure to shield your plants, trees, and other exterior surfaces from runoff or chemical overspray.
Bottom Line
If you want to preserve the life and appearance of your asphalt shingle roof, addressing moss, lichen, and other organic growth quickly is key. The most effective and roof-friendly approach is through professional-style soft washing — a method designed for roof moss removal and long-term maintenance without compromising roof integrity.
Regular care, gentle cleaning, and smart prevention will help your roof stay strong and clean for many years.