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Roofingaka: mineral surface cap sheetaka: granule cap

Cap Sheet

In Plain English

The top layer of a built-up roof that protects everything underneath from sun, rain, and weather.

Definition

The top layer or final ply of a built-up or modified bitumen roofing system, providing the weather-resistant surface exposed to the elements. Cap sheets are typically mineral-surfaced (granule-coated) to reflect UV radiation and protect the underlying bitumen layers from weathering. In modified bitumen systems, the cap sheet is a reinforced polymer-modified membrane.

Example

The cap sheet on the low-slope roof was granule-surfaced in tan to match the building color scheme and reflect solar heat.

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