Asphalt Shingle Granule Loss
Asphalt shingle granule loss is the shedding of the small mineral granules that coat the top of asphalt shingles and shield the asphalt from sunlight. Some loss is normal with age, but heavy loss, bare dark patches, and granules piling up in gutters signal a roof that is wearing out and exposed to UV damage.
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In depth
The granules protect the asphalt layer from UV and add fire resistance. Hail, foot traffic, ice, age, and hard washing knock them loose. Pressure washing a roof is a leading avoidable cause, which is why manufacturers call for soft washing instead. Look for dark grit at the base of downspouts, bald spots, and dark streaks that are bare asphalt rather than algae. Algae can be cleaned, but bare spots cannot be restored. If granules are falling heavily, a roofer should assess the roof.
How this shows up on our jobs
Gutters are where Madison homeowners first see it: a layer of dark grit in the trough. We note heavy granule loss in our reports and never pressure wash a roof.
Services where this matters
Frequently asked
- What is Asphalt Shingle Granule Loss?
- Asphalt shingle granule loss is the shedding of the small mineral granules that coat the top of asphalt shingles and shield the asphalt from sunlight. Some loss is normal with age, but heavy loss, bare dark patches, and granules piling up in gutters signal a roof that is wearing out and exposed to UV damage.
- How does Asphalt Shingle Granule Loss show up on our jobs?
- Gutters are where Madison homeowners first see it: a layer of dark grit in the trough. We note heavy granule loss in our reports and never pressure wash a roof.
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Related terms
Soft Wash
Soft washing is a low-pressure exterior cleaning method that uses biodegradable detergents and a controlled bleach solution to kill the algae, mold, mildew, and bacteria that cause staining — rather than scouring them off with brute force. A soft wash rig delivers cleaning fluid at roughly 60-200 PSI, comparable to a strong garden hose, which is safe on siding, shingles, painted surfaces, screens, and caulking. The chemistry does the work: the solution dwells on the surface, breaks down the organic growth at the cell level, and is then rinsed clean with fresh water.
Gloeocapsa Magma
Gloeocapsa magma is a photosynthetic cyanobacteria that feeds on the limestone calcium carbonate filler embedded in asphalt shingles. It is the organism responsible for the black or dark-gray streaks that run from ridge to eave on millions of American roofs. Algae spores are carried by wind, birds, and squirrels, which is why you'll often see streaks appearing on one slope of a roof before the other, and why entire neighborhoods in Madison begin showing streaks within a few years of each other once the spore population establishes locally.
Roof Moss Treatment
Roof moss treatment is killing moss on a roof with a gentle biocide or soft wash solution and letting rain and wind clear it away, instead of scraping or pressure washing it off. Moss holds moisture against shingles and lifts their edges, but aggressive removal strips granules and does more harm than the moss.
Pressure vs. Volume
Pressure (PSI) and volume (GPM) are the two fundamental outputs of a pressure washer, and understanding the tradeoff between them is the single biggest step an amateur can take toward professional-level results. Pressure is the force of water hitting a single point; volume is the amount of water moving across a surface over time. A high-PSI, low-GPM machine cleans a tiny spot aggressively — great for lifting paint, terrible for washing a driveway. A moderate-PSI, high-GPM machine cleans broadly and gently — great for siding, wood, and most large surfaces.
Gutter Guard
A gutter guard is any cover, screen, insert, or hood system installed over or inside gutters to reduce the amount of debris that enters the trough and clogs the downspouts. There are five main categories: fine-mesh screens (most effective for large debris), micro-mesh (very fine, catches small needles and seeds), solid reverse-curve hoods (water clings and flows in, debris falls off), foam inserts (fill the gutter with foam through which water seeps), and bottle-brush inserts (same concept as foam).