What asphalt-shingle granules actually do
The mineral surface is part of the roofing system. A roof that looks scrubbed clean is not necessarily a roof that was treated gently.
Why the granules exist
Mineral granules cover the weather-facing side of asphalt shingles, helping protect underlying layers from sunlight and exposure. Different shingles use different granules, including some with algae-resistant features.
Loose granules in a gutter can occur as a roof ages. Their presence alone does not identify the cause or prove that a specific cleaning damaged the roof.
Why force matters
ARMA explicitly warns against power washing and scrubbing asphalt shingle surfaces because either may loosen granules. Its guidance is a useful starting point, but the specific shingle manufacturer's instructions take priority.
It is reasonable to question any process that prioritizes a spotless appearance over the integrity of the surface.
Know when to stop
Brittle, cracked, lifted or visibly deteriorated shingles may call for a roofing inspection rather than cosmetic cleaning. Exterior maintenance cannot reverse advanced material failure.
Valley Wise evaluates the condition of the roofing material as part of deciding whether a service is appropriate.
Sources and further reading
- ARMA — Understanding Your Asphalt Shingle Roofing System
- ARMA — Spring Roof Inspection
- ARMA — Algae Discoloration of Roofs
This educational guide does not replace roof manufacturer directions or a qualified inspection. External references are not endorsements of Valley Wise.
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