# Roofing Granules

> Crushed, often ceramic-coated mineral particles embedded in the top surface of asphalt shingles and roll roofing to block UV light and add colour.

- URL: https://roof.wiki/roofing-granules/
- Topic: Roofing Materials
- Also known as: shingle granules; mineral granules; ceramic granules
- Regions: Global
- First published: 2026-11-02 · Last reviewed: 2026-11-02
- Cite as: "Roofing Granules." roof.wiki. https://roof.wiki/roofing-granules/

## Key facts

- **Typical materials:** Crushed rock (e.g. slate, schist, quartz) with ceramic coating
- **Main role:** Protect asphalt from UV; add colour
- **Special types:** Algae-resistant (copper/zinc), cool-roof reflective

Roofing granules are small particles of crushed rock, usually coated with a fired ceramic colour layer, that are pressed into the hot asphalt surface of shingles and mineral-surfaced roll roofing. They form the visible weathering surface of the product.

## Purpose

- **UV protection**: asphalt degrades quickly in sunlight. Granules shade the asphalt and are the main defence against ultraviolet ageing.
- **Colour**: the ceramic coating gives the roof its colour and blend. Lighter colours reflect more heat, which is useful in hot, sunny climates; darker colours absorb heat.
- **Fire resistance**: the mineral layer helps the shingle resist burning brands.
- **Special functions**: some granules are coated with copper or zinc compounds to resist algae, and "cool roof" granules use pigments that reflect near-infrared radiation.

## Materials

Granule materials include slate, schist, quartz, vitrified brick, stone and ceramic. The underside of a shingle uses a finer, non-coloured surfacing such as sand, talc or mica to stop shingles sticking together in the bundle.

## Granule loss

Some granule loss is normal, especially when a roof is new and loose surplus granules wash into the gutters. Ongoing or heavy loss, however, is a sign of ageing: once the asphalt is exposed, it oxidises and cracks faster. Hail can knock granules off in round patches, which is one of the signs adjusters look for after a storm. Pressure washing a shingle roof can strip granules and is generally discouraged by manufacturers.

## Inspection tip

Granules collecting in gutters or at downspout outlets, bare dark patches on shingles, or exposed fibreglass mat all indicate that the roof surface is wearing out.


## Sources

1. Asphalt shingle — Wikipedia. https://en.wikipedia.org/wiki/Asphalt_shingle
2. Algae resistant granules — Malarkey Roofing Products. https://www.malarkeyroofing.com/features/algae-resistant-granules/